NAME

       scons - a software construction tool

SYNOPSIS

       scons [options...] [name=val...] [targets...]

DESCRIPTION

       scons orchestrates the construction of software (and other tangible products such as
       documentation files) by determining which component pieces must be built or rebuilt and
       invoking the necessary commands to build them.  SCons offers many features to improve
       developer productivity such as parallel builds, caching of build artifacts, automatic
       dependency scanning, and a database of information about previous builds so details do not
       have to be recalculated each run.

       scons requires Python 3.6 or later to run; there should be no other dependencies or
       requirements, unless the experimental Ninja tool is used.

       Changed in version 4.3.0: support for Python 3.5 is removed; the CPython project has
       retired 3.5: https://www.python.org/dev/peps/pep-0478.

       You set up an SCons build system by writing a script that describes things to build
       (targets), and, if necessary, the rules to build those files (actions).  SCons comes with
       a collection of Builder methods which apply premade actions for building many common
       software components such as executable programs, object files and libraries, so that for
       many software projects, only the targets and input files (sources) need be specified in a
       call to a builder.  SCons thus can operate at a level of abstraction above that of pure
       filenames. For example if you specify a library target named "foo", SCons keeps track of
       the actual operating system dependent filename (such as libfoo.so on a GNU/Linux system),
       and how to refer to that library in later construction steps that want to use it, so you
       don't have to specify that precise information yourself.  SCons can also scan
       automatically for dependency information, such as header files included by source code
       files (for example, #include preprocessor directives in C or C++ files), so these implicit
       dependencies do not have to be specified manually.  SCons supports the ability to define
       new scanners to support additional input file types.

       Information about files involved in the build, including a cryptographic hash of the
       contents of source files, is cached for later reuse. By default this hash (the content
       signature) is used to determine if a file has changed since the last build, although this
       can be controlled by selecting an appropriate Decider function. Implicit dependency files
       are also part of out-of-date computation. The scanned implicit dependency information can
       optionally be cached and used to speed up future builds. A hash of each executed build
       action (the build signature) is cached, so that changes to build instructions (changing
       flags, etc.) or to the build tools themselves (new version) can also trigger a rebuild.

       SCons supports the concept of separated source and build directories through the
       definition of variant directories (see the VariantDir function).

       When invoked, scons looks for a file named SConstruct in the current directory and reads
       the build configuration from that file (other names are allowed, see the section called
       “SConscript Files” and the -f option for more information). The build may be structured in
       a hierarchical manner: the SConstruct file may specify subsidiary configuration files by
       calling the SConscript function, and these may, in turn, do the same. By convention, these
       subsidiary files are named SConscript, although any name may be used. As a result of this
       naming convention, the term SConscript files is used to refer generically to the complete
       set of configuration files for a project (including the SConstruct file), regardless of
       the actual file names or number of such files. A hierarchical build is not recursive - all
       of the SConscript files are processed in a single pass, although each is processed in a
       separate context so as not to interfere with one another.  SCons provides mechanisms for
       information to be shared between SConscript files when needed.

       Before reading the SConscript files, scons looks for a directory named site_scons in
       various system directories and in the directory containing the SConstruct file or, if
       specified, the directory from the --site-dir option instead, and prepends the ones it
       finds to the Python module search path (sys.path), thus allowing modules in such
       directories to be imported in the normal Python way in SConscript files. For each found
       site directory, (1) if it contains a file site_init.py that file is evaluated, and (2) if
       it contains a directory site_tools the path to that directory is prepended to the default
       toolpath. See the --site-dir and --no-site-dir options for details on default paths and
       controlling the site directories.

       SConscript files are written in the Python programming language, although it is normally
       not necessary to be a Python programmer to use scons effectively.  SConscript files are
       invoked in a context that makes the facilities described in this manual page available in
       their local namespace without any special steps. Standard Python scripting capabilities
       such as flow control, data manipulation, and imported Python libraries are available to
       use to handle complicated build situations. Other Python files can be made a part of the
       build system, but they do not automatically have the SCons context and need to import it
       if they need access (described later).

       scons reads and executes all of the included SConscript files before it begins building
       any targets. To make this clear, scons prints the following messages about what it is
       doing:

           $ scons foo.out
           scons: Reading SConscript files ...
           scons: done reading SConscript files.
           scons: Building targets  ...
           cp foo.in foo.out
           scons: done building targets.
           $

       The status messages (lines beginning with the scons: tag) may be suppressed using the -Q
       option.

       To assure reproducible builds, SCons uses a restricted execution environment for running
       external commands used to build targets, rather then propagating the full environment in
       effect at the time scons was called. This helps avoid problems like picking up accidental
       settings, temporary debug values that are no longer needed, or one developer having
       different settings than another (or than the CI/CD pipeline). Environment variables that
       are needed for proper operation of such commands need to be set explicitly, which can be
       done either by assigning the desired values, or by picking values individually out of
       environment variables using the Python os.environ dictionary. The execution environment
       for a given construction environment is contained in its $ENV construction variable. A few
       environment variables are picked up automatically - see the section called “ENVIRONMENT”).

       In particular, if the compiler or other commands that you want to use to build your target
       files are not in standard system locations, scons will not find them unless you explicitly
       include the locations into the PATH element of the execution environment. One example
       approach is to extract the entire PATH environment variable and set that into the
       execution environment:

           import os
           env = Environment(ENV={'PATH': os.environ['PATH']})

       Similarly, if the commands use specific external environment variables that scons does not
       recognize, they can be propagated into the execution environment:

           import os

           env = Environment(
               ENV={
                   'PATH': os.environ['PATH'],
                   'ANDROID_HOME': os.environ['ANDROID_HOME'],
                   'ANDROID_NDK_HOME': os.environ['ANDROID_NDK_HOME'],
               }
           )

       Or you may explicitly propagate the invoking user's complete external environment:

           import os
           env = Environment(ENV=os.environ.copy())

       This comes at the expense of making your build dependent on the user's environment being
       set correctly, but it may be more convenient for many configurations. It should not cause
       problems if done in a build setup which tightly controls how the environment is set up
       before invoking scons, as in many continuous integration setups.

       scons is normally executed in a top-level directory containing an SConstruct file. When
       scons is invoked, the command line (including the contents of the SCONSFLAGS environment
       variable, if set) is processed. Command-line options (see the section called “OPTIONS”)
       are consumed. Any variable argument assignments are collected, and remaining arguments are
       taken as targets to build.

       Values of variables to be passed to the SConscript files may be specified on the command
       line:

           scons debug=1

       These variables are available through the ARGUMENTS dictionary, and can be used in the
       SConscript files to modify the build in any way:

           if ARGUMENTS.get('debug', 0):
               env = Environment(CCFLAGS='-g')
           else:
               env = Environment()

       The command-line variable arguments are also available in the ARGLIST list, indexed by
       their order on the command line. This allows you to process them in order rather than by
       name, if necessary. Each ARGLIST entry is a tuple containing (argname, argvalue).

       See the section called “Command-Line Construction Variables” for more information.

       scons can maintain a cache of target (derived) files that can be shared between multiple
       builds. When derived-file caching is enabled in an SConscript file, any target files built
       by scons will be copied to the cache. If an up-to-date target file is found in the cache,
       it will be retrieved from the cache instead of being rebuilt locally. Caching behavior may
       be disabled and controlled in other ways by the --cache-force, --cache-disable,
       --cache-readonly, and --cache-show command-line options. The --random option is useful to
       prevent multiple builds from trying to update the cache simultaneously.

       By default, scons searches for known programming tools on various systems and initializes
       itself based on what is found. On Windows systems which identify as win32, scons searches
       in order for the Microsoft Visual C++ tools, the MinGW tool chain, the Intel compiler
       tools, and the PharLap ETS compiler. On Windows system which identify as cygwin (that is,
       if scons is invoked from a cygwin shell), the order changes to prefer the GCC toolchain
       over the MSVC tools. On OS/2 systems, scons searches in order for the OS/2 compiler, the
       GCC tool chain, and the Microsoft Visual C++ tools, On SGI IRIX, IBM AIX, Hewlett Packard
       HP-UX, and Oracle Solaris systems, scons searches for the native compiler tools (MIPSpro,
       Visual Age, aCC, and Forte tools respectively) and the GCC tool chain. On all other
       platforms, including POSIX (Linux and UNIX) platforms, scons searches in order for the GCC
       tool chain, and the Intel compiler tools. These default values may be overridden by
       appropriate setting of construction variables.

   Target Selection
       SCons acts on the selected targets, whether the requested operation is build, no-exec or
       clean. Targets are selected as follows:

        1. Targets specified on the command line. These may be files, directories, or phony
           targets defined using the Alias function. Directory targets are scanned by scons for
           any targets that may be found with a destination in or under that directory. The
           targets listed on the command line are made available in the COMMAND_LINE_TARGETS
           list.

        2. If no targets are specified on the command line, scons will select those targets
           specified in the SConscript files via calls to the Default function. These are known
           as the default targets, and are made available in the DEFAULT_TARGETS list.

        3. If no targets are selected by the previous steps, scons selects the current directory
           for scanning, unless command-line options which affect the directory for target
           scanning are present (-C, -D, -u, -U). Since targets thus selected were not the result
           of user instructions, this target list is not made available for direct inspection;
           use the --debug=explain option if they need to be examined.

        4.  scons always adds to the selected targets any intermediate targets which are
           necessary to build the specified ones. For example, if constructing a shared library
           or dll from C source files, scons will also build the object files which will make up
           the library.

       To ignore the default targets specified through calls to Default and instead build all
       target files in or below the current directory specify the current directory (.) as a
       command-line target:

           scons .

       To build all target files, including any files outside of the current directory, supply a
       command-line target of the root directory (on POSIX systems):

           scons /

       or the path name(s) of the volume(s) in which all the targets should be built (on Windows
       systems):

           scons C:\ D:\

       A subset of a hierarchical tree may be built by remaining at the top-level directory
       (where the SConstruct file lives) and specifying the subdirectory as the target to build:

           scons src/subdir

       or by changing directory and invoking scons with the -u option, which traverses up the
       directory hierarchy until it finds the SConstruct file, and then builds targets relatively
       to the current subdirectory (see also the related -D and -U options):

           cd src/subdir
           scons -u .

       In all cases, more files may be built than are requested, as scons needs to make sure any
       dependent files are built.

       Specifying "cleanup" targets in SConscript files is usually not necessary. The -c flag
       removes all selected targets:

           scons -c .

       to remove all target files in or under the current directory, or:

           scons -c build export

       to remove target files under build and export.

       Additional files or directories to remove can be specified using the Clean function in the
       SConscript files. Conversely, targets that would normally be removed by the -c invocation
       can be retained by calling the NoClean function with those targets.

       scons supports building multiple targets in parallel via a -j option that takes, as its
       argument, the number of simultaneous tasks that may be spawned:

           scons -j 4

       builds four targets in parallel, for example.

OPTIONS

       In general, scons supports the same command-line options as GNU Make and many of those
       supported by cons.

       -b
           Ignored for compatibility with non-GNU versions of Make

       -c, --clean, --remove
           Set clean mode. Clean up by removing the selected targets, well as any files or
           directories associated with a selected target through calls to the Clean function.
           Will not remove any targets which are marked for preservation through calls to the
           NoClean function.

           While clean mode removes targets rather than building them, work which is done
           directly in Python code in SConscript files will still be carried out. If it is
           important to avoid some such work from taking place in clean mode, it should be
           protected. An SConscript file can determine which mode is active by querying
           GetOption, as in the call if GetOption("clean"):

       --cache-debug=file
           Write debug information about derived-file caching to the specified file. If file is a
           hyphen (-), the debug information is printed to the standard output. The printed
           messages describe what signature-file names are being looked for in, retrieved from,
           or written to the derived-file cache specified by CacheDir.

       --cache-disable, --no-cache
           Disable derived-file caching.  scons will neither retrieve files from the cache nor
           copy files to the cache. This option can be used to temporarily disable the cache
           without modifying the build scripts.

       --cache-force, --cache-populate
           When using CacheDir, populate a derived-file cache by copying any already-existing,
           up-to-date derived files to the cache, in addition to files built by this invocation.
           This is useful to populate a new cache with all the current derived files, or to add
           to the cache any derived files recently built with caching disabled via the
           --cache-disable option.

       --cache-readonly
           Use the derived-file cache, if enabled, to retrieve files, but do not not update the
           cache with any files actually built during this invocation.

       --cache-show
           When using a derived-file cache show the command that would have been executed to
           build the file (or the corresponding *COMSTR contents if set) even if the file is
           retrieved from cache. Without this option, scons shows a cache retrieval message if
           the file is fetched from cache. This allows producing consistent output for build
           logs, regardless of whether a target file was rebuilt or retrieved from the cache.

       --config=mode
           Control how the Configure call should use or generate the results of configuration
           tests.  mode should be one of the following choices:

           auto
               SCons will use its normal dependency mechanisms to decide if a test must be
               rebuilt or not. This saves time by not running the same configuration tests every
               time you invoke scons, but will overlook changes in system header files or
               external commands (such as compilers) if you don't specify those dependecies
               explicitly. This is the default behavior.

           force
               If this mode is specified, all configuration tests will be re-run regardless of
               whether the cached results are out of date. This can be used to explicitly force
               the configuration tests to be updated in response to an otherwise unconfigured
               change in a system header file or compiler.

           cache
               If this mode is specified, no configuration tests will be rerun and all results
               will be taken from cache.  scons will report an error if --config=cache is
               specified and a necessary test does not have any results in the cache.

       -C directory, --directory=directory
           Run as if scons was started in directory instead of the current working directory.
           That is, change directory before searching for the SConstruct, Sconstruct, sconstruct,
           SConstruct.py, Sconstruct.py or sconstruct.py file or doing anything else. When
           multiple -C options are given, each subsequent non-absolute -C directory is
           interpreted relative to the preceding one. This option is similar to using -f
           directory/SConstruct, but -f does not search for any of the predefined SConstruct
           names in the specified directory. See also options -u, -U and -D to change the
           SConstruct search behavior when this option is used.

       -D
           Works exactly the same way as the -u option except for the way default targets are
           handled. When this option is used and no targets are specified on the command line,
           all default targets are built, whether or not they are below the current directory.

       --debug=type[,type...]
           Debug the build process.  type specifies the kind of debugging info to emit. Multiple
           types may be specified, separated by commas. The following types are recognized:

           action-timestamps
               Prints additional time profiling information. For each command, shows the absolute
               start and end times. This may be useful in debugging parallel builds. Implies the
               --debug=time option.

               New in version 3.1.

           count
               Print how many objects are created of the various classes used internally by SCons
               before and after reading the SConscript files and before and after building
               targets. This is not supported when SCons is executed with the Python -O
               (optimized) option or when the SCons modules have been compiled with optimization
               (that is, when executing from *.pyo files).

           duplicate
               Print a line for each unlink/relink (or copy) of a file in a variant directory
               from its source file. Includes debugging info for unlinking stale variant
               directory files, as well as unlinking old targets before building them.

           explain
               Print an explanation of why scons is deciding to (re-)build the targets it selects
               for building.

           findlibs
               Instruct the scanner that searches for libraries to print a message about each
               potential library name it is searching for, and about the actual libraries it
               finds.

           includes
               Print the include tree after each top-level target is built. This is generally
               used to find out what files are included by the sources of a given derived file:

                   $ scons --debug=includes foo.o

           memoizer
               Prints a summary of hits and misses using the Memoizer, an internal subsystem that
               counts how often SCons uses cached values in memory instead of recomputing them
               each time they're needed.

           memory
               Prints how much memory SCons uses before and after reading the SConscript files
               and before and after building targets.

           objects
               Prints a list of the various objects of the various classes used internally by
               SCons.

           pdb
               Re-run scons under the control of the pdb Python debugger.

           prepare
               Print a line each time any target (internal or external) is prepared for building.
               scons prints this for each target it considers, even if that target is up to date
               (see also --debug=explain). This can help debug problems with targets that aren't
               being built; it shows whether scons is at least considering them or not.

           presub
               Print the raw command line used to build each target before the construction
               environment variables are substituted. Also shows which targets are being built by
               this command. Output looks something like this:

                   $ scons --debug=presub
                   Building myprog.o with action(s):
                     $SHCC $SHCFLAGS $SHCCFLAGS $CPPFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
                   ...

           stacktrace
               Prints an internal Python stack trace when encountering an otherwise unexplained
               error.

           time
               Prints various time profiling information:

               •   The time spent executing each individual build command

               •   The total build time (time SCons ran from beginning to end)

               •   The total time spent reading and executing SConscript files

               •   The total time SCons itself spent running (that is, not counting reading and
                   executing SConscript files)

               •   The total time spent executing all build commands

               •   The elapsed wall-clock time spent executing those build commands

               •   The time spent processing each file passed to the SConscript function

               (When scons is executed without the -j option, the elapsed wall-clock time will
               typically be slightly longer than the total time spent executing all the build
               commands, due to the SCons processing that takes place in between executing each
               command. When scons is executed with the -j option, and your build configuration
               allows good parallelization, the elapsed wall-clock time should be significantly
               smaller than the total time spent executing all the build commands, since multiple
               build commands and intervening SCons processing should take place in parallel.)

       --diskcheck=type
           Enable specific checks for whether or not there is a file on disk where the SCons
           configuration expects a directory (or vice versa) when searching for source and
           include files.  type can be an available diskcheck type or the special tokens all or
           none. A comma-separated string can be used to select multiple checks. The default
           setting is all.

           Current available checks are:

           match
               to check that files and directories on disk match SCons' expected configuration.

           Disabling some or all of these checks can provide a performance boost for large
           configurations, or when the configuration will check for files and/or directories
           across networked or shared file systems, at the slight increased risk of an incorrect
           build or of not handling errors gracefully.

       --duplicate=ORDER
           There are three ways to duplicate files in a build tree: hard links, soft (symbolic)
           links and copies. The default policy is to prefer hard links to soft links to copies.
           You can specify a different policy with this option.  ORDER must be one of
           hard-soft-copy (the default), soft-hard-copy, hard-copy, soft-copy or copy.  SCons
           will attempt to duplicate files using the mechanisms in the specified order.

       --enable-virtualenv
           Import virtualenv-related variables to SCons.

       --experimental=feature
           Enable experimental features and/or tools.  feature can be an available feature name
           or the special tokens all or none. A comma-separated string can be used to select
           multiple features. The default setting is none.

           Current available features are: ninja (added in version 4.2), tm_v2 (added in version
           4.4.1).

               Caution
               No Support offered for any features or tools enabled by this flag.
           New in version 4.2 (experimental).

       -f file, --file=file, --makefile=file, --sconstruct=file
           Use file as the initial SConscript file. Multiple -f options may be specified, in
           which case scons will read all of the specified files.

       -h, --help
           Print a local help message for this project, if one is defined in the SConscript files
           (see the Help function), plus a line that refers to the standard SCons help message.
           If no local help message is defined, prints the standard SCons help message (as for
           the -H option) plus help for any local options defined through AddOption. Exits after
           displaying the appropriate message.

           Note that use of this option requires SCons to process the SConscript files, so syntax
           errors may cause the help message not to be displayed.

       --hash-chunksize=KILOBYTES
           Set the block size used when computing content signatures to KILOBYTES. This value
           determines the size of the chunks which are read in at once when computing signature
           hashes. Files below that size are fully stored in memory before performing the
           signature computation while bigger files are read in block-by-block. A huge block-size
           leads to high memory consumption while a very small block-size slows down the build
           considerably.

           The default value is to use a chunk size of 64 kilobytes, which should be appropriate
           for most uses.

           New in version 4.2.

       --hash-format=ALGORITHM
           Set the hashing algorithm used by SCons to ALGORITHM. This value determines the
           hashing algorithm used in generating content signatures, build signatures and CacheDir
           keys.

           The supported list of values are: md5, sha1 and sha256. However, the Python
           interpreter used to run scons must have the corresponding support available in the
           hashlib module to use the specified algorithm.

           If this option is omitted, the first supported hash format found is selected.
           Typically this is MD5, however, on a FIPS-compliant system using a version of Python
           older than 3.9, SHA1 or SHA256 is chosen as the default.  Python 3.9 and onwards
           clients always default to MD5, even in FIPS mode.

           Specifying this option changes the name of the SConsign database. The default database
           is .sconsign.dblite. In the presence of this option, ALGORITHM is included in the name
           to indicate the difference, even if the argument is md5. For example,
           --hash-format=sha256 uses a SConsign database named .sconsign_sha256.dblite.

           New in version 4.2.

       -H, --help-options
           Print the standard help message about SCons command-line options and exit.

       -i, --ignore-errors
           Ignore all errors from commands executed to rebuild files.

       -I directory, --include-dir=directory
           Specifies a directory to search for imported Python modules. If several -I options are
           used, the directories are searched in the order specified.

       --ignore-virtualenv
           Suppress importing virtualenv-related variables to SCons.

       --implicit-cache
           Cache implicit dependencies. This causes scons to use the implicit (scanned)
           dependencies from the last time it was run instead of scanning the files for implicit
           dependencies. This can significantly speed up SCons, but with the following
           limitations:

           scons will not detect changes to implicit dependency search paths (e.g.  $CPPPATH,
           $LIBPATH) that would ordinarily cause different versions of same-named files to be
           used.

           scons will miss changes in the implicit dependencies in cases where a new implicit
           dependency is added earlier in the implicit dependency search path (e.g.  $CPPPATH,
           $LIBPATH) than a current implicit dependency with the same name.

       --implicit-deps-changed
           Forces SCons to ignore the cached implicit dependencies. This causes the implicit
           dependencies to be rescanned and recached. This implies --implicit-cache.

       --implicit-deps-unchanged
           Force SCons to ignore changes in the implicit dependencies. This causes cached
           implicit dependencies to always be used. This implies --implicit-cache.

       --install-sandbox=sandbox_path
           When using the Install builders, prepend sandbox_path to the installation paths such
           that all installed files will be placed under that directory. This option is
           unavailable if one of Install, InstallAs or InstallVersionedLib is not used in the
           SConscript files.

       --interactive
           Starts SCons in interactive mode. The SConscript files are read once and a scons>>>
           prompt is printed. Targets may now be rebuilt by typing commands at interactive prompt
           without having to re-read the SConscript files and re-initialize the dependency graph
           from scratch.

           SCons interactive mode supports the following commands:

           build [OPTIONS] [TARGETS] ...
               Builds the specified TARGETS (and their dependencies) with the specified SCons
               command-line OPTIONS.  b and scons are synonyms for build.

               The following SCons command-line options affect the build command:

                   --cache-debug=FILE
                   --cache-disable, --no-cache
                   --cache-force, --cache-populate
                   --cache-readonly
                   --cache-show
                   --debug=TYPE
                   -i, --ignore-errors
                   -j N, --jobs=N
                   -k, --keep-going
                   -n, --no-exec, --just-print, --dry-run, --recon
                   -Q
                   -s, --silent, --quiet
                   --taskmastertrace=FILE
                   --tree=OPTIONS

               Any other SCons command-line options that are specified do not cause errors but
               have no effect on the build command (mainly because they affect how the SConscript
               files are read, which only happens once at the beginning of interactive mode).

           clean [OPTIONS] [TARGETS] ...
               Cleans the specified TARGETS (and their dependencies) with the specified OPTIONS.
               c is a synonym. This command is itself a synonym for build --clean

           exit
               Exits SCons interactive mode. You can also exit by terminating input (Ctrl+D UNIX
               or Linux systems, (Ctrl+Z on Windows systems).

           help [COMMAND]
               Provides a help message about the commands available in SCons interactive mode. If
               COMMAND is specified, h and ?  are synonyms.

           shell [COMMANDLINE]
               Executes the specified COMMANDLINE in a subshell. If no COMMANDLINE is specified,
               executes the interactive command interpreter specified in the SHELL environment
               variable (on UNIX and Linux systems) or the COMSPEC environment variable (on
               Windows systems).  sh and !  are synonyms.

           version
               Prints SCons version information.

           An empty line repeats the last typed command. Command-line editing can be used if the
           readline module is available.

               $ scons --interactive
               scons: Reading SConscript files ...
               scons: done reading SConscript files.
               scons>>> build -n prog
               scons>>> exit

       -j N, --jobs=N
           Specifies the maximum number of comcurrent jobs (commands) to run. If there is more
           than one -j option, the last one is effective.

       -k, --keep-going
           Continue as much as possible after an error. The target that failed and those that
           depend on it will not be remade, but other targets specified on the command line will
           still be processed.

       -m
           Ignored for compatibility with non-GNU versions of Make.

       --max-drift=SECONDS
           Set the maximum expected drift in the modification time of files to SECONDS. This
           value determines how long a file must be unmodified before its cached content
           signature will be used instead of calculating a new content signature (hash) of the
           file's contents. The default value is 2 days, which means a file must have a
           modification time of at least two days ago in order to have its cached content
           signature used. A negative value means to never cache the content signature and to
           ignore the cached value if there already is one. A value of 0 means to always use the
           cached signature, no matter how old the file is.

       --md5-chunksize=KILOBYTES
           A deprecated synonym for --hash-chunksize.

           Changed in version 4.2: deprecated.

       -n, --no-exec, --just-print, --dry-run, --recon
           Set no-exec mode. Print the commands that would be executed to build any out-of-date
           targets, but do not execute those commands.

           Only target building is suppressed - any work in the build system that is done
           directly (in regular Python code) will still be carried out. You can add guards around
           code which should not be executed in no-exec mode by checking the value of the option
           at run time with GetOption:

               if not GetOption("no_exec"):
                   # run regular instructions

           The output is a best effort, as SCons cannot always precisely determine what would be
           built. For example, if a file generated by a builder action is also used as a source
           in the build, that file is not available to scan for dependencies at all in an unbuilt
           tree, and may contain out of date information in a previously built tree.

       --no-site-dir
           Prevents the automatic addition of the standard site_scons directories to sys.path.
           Also prevents loading the site_scons/site_init.py modules if they exist, and prevents
           adding their site_scons/site_tools directories to the toolpath.

       --package-type=type
           The type of package to create when using the Package builder. Multiple types can be
           specified by using a comma-separated string, in which case SCons will try to build for
           all of those package types. Note this option is only available if the packaging tool
           has been enabled.

       --profile=file
           Run SCons under the Python profiler and save the results to file. The results may be
           analyzed using the Python pstats module.

       -q, --question
           Do not run any commands, or print anything. Just return an exit status that is zero if
           the specified targets are already up to date, non-zero otherwise.

       -Q
           Suppress status messages about reading SConscript files, building targets and entering
           directories. Commands that are executed to rebuild target files are still printed.

       --random
           Build dependencies in a random order. This is useful when building multiple trees
           simultaneously with caching enabled, to prevent multiple builds from simultaneously
           trying to build or retrieve the same target files.

       -s, --silent, --quiet
           Silent. Do not print commands that are executed to rebuild target files. Also
           suppresses SCons status messages.

       -S, --no-keep-going, --stop
           Ignored for compatibility with GNU Make

       --site-dir=path
           Use a specific path as the site directory rather than searching the list of default
           site directories. This directory will be prepended to sys.path, the module
           path/site_init.py will be loaded if it exists, and path/site_tools will be added to
           the default toolpath.

           The default set of site directories searched when --site-dir is not specified depends
           on the system platform, as follows. Users or system administrators can tune
           site-specific or project-specific SCons behavior by setting up a site directory in one
           or more of these locations. Directories are examined in the order given, from most
           generic ("system" directories) to most specific (in the current project), so the
           last-executed site_init.py file is the most specific one, giving it the chance to
           override everything else), and the directories are prepended to the paths, again so
           the last directory examined comes first in the resulting path.

           Windows:

                   %ALLUSERSPROFILE%/scons/site_scons
                   %LOCALAPPDATA%/scons/site_scons
                   %APPDATA%/scons/site_scons
                   %USERPROFILE%/.scons/site_scons
                   ./site_scons

               Note earlier versions of the documentation listed a different path for the
               "system" site directory, this path is still checked but its use is discouraged:

                   %ALLUSERSPROFILE%/Application Data/scons/site_scons

           Mac OS X:

                   /Library/Application Support/SCons/site_scons
                   /opt/local/share/scons/site_scons (for MacPorts)
                   /sw/share/scons/site_scons (for Fink)
                   $HOME/Library/Application Support/SCons/site_scons
                   $HOME/.scons/site_scons
                   ./site_scons

           Solaris:

                   /opt/sfw/scons/site_scons
                   /usr/share/scons/site_scons
                   $HOME/.scons/site_scons
                   ./site_scons

           Linux, HPUX, and other Posix-like systems:

                   /usr/share/scons/site_scons
                   $HOME/.scons/site_scons
                   ./site_scons

       --stack-size=KILOBYTES
           Set the size stack used to run threads to KILOBYTES. This value determines the stack
           size of the threads used to run jobs. These threads execute the actions of the
           builders for the nodes that are out-of-date. This option has no effect unless the
           number of concurrent build jobs is larger than one (as set by -j N or --jobs=N on the
           command line or SetOption in a script).

           Using a stack size that is too small may cause stack overflow errors. This usually
           shows up as segmentation faults that cause scons to abort before building anything.
           Using a stack size that is too large will cause scons to use more memory than required
           and may slow down the entire build process. The default value is to use a stack size
           of 256 kilobytes, which should be appropriate for most uses. You should not need to
           increase this value unless you encounter stack overflow errors.

       -t, --touch
           Ignored for compatibility with GNU Make. (Touching a file to make it appear up-to-date
           is unnecessary when using scons.)

       --taskmastertrace=file
           Prints trace information to the specified file about how the internal Taskmaster
           object evaluates and controls the order in which Nodes are built. A file name of - may
           be used to specify the standard output.

       --tree=type[,type...]
           Prints a tree of the dependencies after each top-level target is built. This prints
           out some or all of the tree, in various formats, depending on the type specified:

           all
               Print the entire dependency tree after each top-level target is built. This prints
               out the complete dependency tree, including implicit dependencies and ignored
               dependencies.

           derived
               Restricts the tree output to only derived (target) files, not source files.

           linedraw
               Draw the tree output using Unicode line-drawing characters instead of plain ASCII
               text. This option acts as a modifier to the selected type(s). If specified alone,
               without any type, it behaves as if all had been specified.

               New in version 4.0.

           status
               Prints status information for each displayed node.

           prune
               Prunes the tree to avoid repeating dependency information for nodes that have
               already been displayed. Any node that has already been displayed will have its
               name printed in [square brackets], as an indication that the dependencies for that
               node can be found by searching for the relevant output higher up in the tree.

           Multiple type choices may be specified, separated by commas:

               # Prints only derived files, with status information:
               scons --tree=derived,status

               # Prints all dependencies of target, with status information
               # and pruning dependencies of already-visited Nodes:
               scons --tree=all,prune,status target

       -u, --up, --search-up
           Walks up the directory structure until an SConstruct, Sconstruct, sconstruct,
           SConstruct.py, Sconstruct.py or sconstruct.py file is found, and uses that as the top
           of the directory tree. If no targets are specified on the command line, only targets
           at or below the current directory will be built.

       -U
           Works exactly the same way as the -u option except for the way default targets are
           handled. When this option is used and no targets are specified on the command line,
           all default targets that are defined in the SConscript file(s) in the current
           directory are built, regardless of what directory the resultant targets end up in.

       -v, --version
           Print the scons version, copyright information, list of authors, and any other
           relevant information. Then exit.

       -w, --print-directory
           Print a message containing the working directory before and after other processing.

       --no-print-directory
           Turn off -w, even if it was turned on implicitly.

       --warn=type, --warn=no-type
           Enable or disable (with the prefix "no-") warnings (--warning is a synonym).  type
           specifies the type of warnings to be enabled or disabled:

           all
               All warnings.

           cache-version
               Warnings about the derived-file cache directory specified by CacheDir not using
               the latest configuration information. These warnings are enabled by default.

           cache-write-error
               Warnings about errors trying to write a copy of a built file to a specified
               derived-file cache specified by CacheDir. These warnings are disabled by default.

           corrupt-sconsign
               Warnings about unfamiliar signature data in .sconsign files. These warnings are
               enabled by default.

           dependency
               Warnings about dependencies. These warnings are disabled by default.

           deprecated
               Warnings about use of currently deprecated features. These warnings are enabled by
               default. Not all deprecation warnings can be disabled with the
               --warn=no-deprecated option as some deprecated features which are late in the
               deprecation cycle may have been designated as mandatory warnings, and these will
               still display. Warnings for certain deprecated features may also be enabled or
               disabled individually; see below.

           duplicate-environment
               Warnings about attempts to specify a build of a target with two different
               construction environments that use the same action. These warnings are enabled by
               default.

           fortran-cxx-mix
               Warnings about linking Fortran and C++ object files in a single executable, which
               can yield unpredictable behavior with some compilers.

           future-deprecated
               Warnings about features that will be deprecated in the future. Such warnings are
               disabled by default. Enabling future deprecation warnings is recommended for
               projects that redistribute SCons configurations for other users to build, so that
               the project can be warned as soon as possible about to-be-deprecated features that
               may require changes to the configuration.

           link
               Warnings about link steps.

           misleading-keywords
               Warnings about the use of two commonly misspelled keywords targets and sources to
               Builder calls. The correct spelling is the singular form, even though target and
               source can themselves refer to lists of names or nodes.

           tool-qt-deprecated
               Warnings about the qt tool being deprecated. These warnings are disabled by
               default for the first phase of deprecation. Enable to be reminded about use of
               this tool module.  New in version 4.3.

           missing-sconscript
               Warnings about missing SConscript files. These warnings are enabled by default.

           no-object-count
               Warnings about the --debug=object feature not working when scons is run with the
               Python -O option or from optimized Python (.pyo) modules.

           no-parallel-support
               Warnings about the version of Python not being able to support parallel builds
               when the -j option is used. These warnings are enabled by default.

           python-version
               Warnings about running SCons using a version of Python that has been deprecated.
               These warnings are enabled by default.

           reserved-variable
               Warnings about attempts to set the reserved construction variable names
               $CHANGED_SOURCES, $CHANGED_TARGETS, $TARGET, $TARGETS, $SOURCE, $SOURCES,
               $UNCHANGED_SOURCES or $UNCHANGED_TARGETS. These warnings are disabled by default.

           stack-size
               Warnings about requests to set the stack size that could not be honored. These
               warnings are enabled by default.

           target_not_build
               Warnings about a build rule not building the expected targets. These warnings are
               disabled by default.

       -Y repository, --repository=repository, --srcdir=repository
           Search the specified repository for any input and target files not found in the local
           directory hierarchy. Multiple -Y options may be specified, in which case the
           repositories are searched in the order specified.

SCONSCRIPT FILE REFERENCE

   SConscript Files
       The build configuration is described by one or more files, known as SConscript files.
       There must be at least one file for a valid build (scons will quit if it does not find
       one).  scons by default looks for this file by the name SConstruct in the directory from
       which you run scons, though if necessary, also looks for alternative file names
       Sconstruct, sconstruct, SConstruct.py, Sconstruct.py and sconstruct.py in that order. A
       different file name (which can include a pathname part) may be specified via the -f
       option. Except for the SConstruct file, these files are not searched for automatically;
       you add additional configuration files to the build by calling the SConscript function.
       This allows parts of the build to be conditionally included or excluded at run-time
       depending on how scons is invoked.

       Each SConscript file in a build configuration is invoked independently in a separate
       context. This provides necessary isolation so that different parts of the build don't
       accidentally step on each other. You have to be explicit about sharing information, by
       using the Export function or the exports argument to the SConscript function, as well as
       the Return function in a called SConscript file, and comsume shared information by using
       the Import function.

       The following sections describe the various SCons facilities that can be used in
       SConscript files. Quick links:
           Construction Environments
           Tools
           Builder Methods
           Methods and Functions to do Things
           SConscript Variables
           Construction Variables
           Configure Contexts
           Command-Line Construction Variables
           Node Objects

   Construction Environments
       A Construction Environment is the basic means by which you communicate build information
       to SCons. A new construction environment is created using the Environment function:

           env = Environment()

       Construction environment attributes called Construction Variables may be set either by
       specifying them as keyword arguments when the object is created or by assigning them a
       value after the object is created. These two are nominally equivalent:

           env = Environment(FOO='foo')
           env['FOO'] = 'foo'

       Note that certain settings which affect tool detection are referenced only when the tools
       are initializided, so you either need either to supply them as part of the call to
       Environment, or defer tool initialization. For example, initializing the Microsoft Visual
       C++ version you wish to use:

           # initializes msvc to v14.1
           env = Environment(MSVC_VERSION="14.1")

           env = Environment()
           # msvc tool was initialized to default, does not reinitialize
           env['MSVC_VERSION'] = "14.1"

           env = Environment(tools=[])
           env['MSVC_VERSION'] = "14.1"
           # msvc tool initialization was deferred, so will pick up new value
           env.Tool('default')

       As a convenience, construction variables may also be set or modified by the parse_flags
       keyword argument during object creation, which has the effect of the env.MergeFlags method
       being applied to the argument value after all other processing is completed. This is
       useful either if the exact content of the flags is unknown (for example, read from a
       control file) or if the flags need to be distributed to a number of construction
       variables.  env.ParseFlags describes how these arguments are distributed to construction
       variables.

           env = Environment(parse_flags='-Iinclude -DEBUG -lm')

       This example adds 'include' to the $CPPPATH construction variable, 'EBUG' to $CPPDEFINES,
       and 'm' to $LIBS.

       An existing construction environment can be duplicated by calling the env.Clone method.
       Without arguments, it will be a copy with the same settings. Otherwise, env.Clone takes
       the same arguments as Environment, and uses the arguments to create a modified copy.

       SCons provides a special construction environment called the Default Environment. The
       default environment is used only for global functions, that is, construction activities
       called without the context of a regular construction environment. See DefaultEnvironment
       for more information.

       By default, a new construction environment is initialized with a set of builder methods
       and construction variables that are appropriate for the current platform. The optional
       platform keyword argument may be used to specify that the construction environment should
       be initialized for a different platform:

           env = Environment(platform='cygwin')

       Specifying a platform initializes the appropriate construction variables in the
       environment to use and generate file names with prefixes and suffixes appropriate for that
       platform.

       Note that the win32 platform adds the SystemDrive and SystemRoot variables from the user's
       external environment to the construction environment's ENV dictionary. This is so that any
       executed commands that use sockets to connect with other systems will work on Windows
       systems.

       The platform argument may be a string value representing one of the pre-defined platforms
       (aix, cygwin, darwin, hpux, irix, os2, posix, sunos or win32), or it may be be a callable
       platform object returned by a call to Platform selecting a pre-defined platform, or it may
       be a user-supplied callable, in which case the Environment method will call it to update
       the new construction environment:

           def my_platform(env):
               env['VAR'] = 'xyzzy'

           env = Environment(platform=my_platform)

       Note that supplying a non-default platform or custom fuction for initialization may bypass
       settings that should happen for the host system and should be used with care. It is most
       useful in the case where the platform is an alternative for the one that would be
       auto-detected, such as platform="cygwin" on a system which would otherwise identify as
       win32.

       The optional tools and toolpath keyword arguments affect the way tools available to the
       environment are initialized. See the section called “Tools” for details.

       The optional variables keyword argument allows passing a Variables object which will be
       used in the initialization of the construction environment See the section called
       “Command-Line Construction Variables” for details.

   Tools
       SCons has a large number of predefined tool modules (more properly, tool specification
       modules) which are used to help initialize the construction environment. An SCons tool is
       only responsible for setup. For example, if an SConscript file declares the need to
       construct an object file from a C-language source file by calling the Object builder, then
       a tool representing an available C compiler needs to have run first, to set up that
       builder and all the construction variables it needs in the associated construction
       environment; the tool itself is not called in the process of the build. Normally this
       happens invisibly as scons has per-platform lists of default tools, and it steps through
       those tools, calling the ones which are actually applicable, skipping those where
       necessary programs are not installed on the build system, or other preconditions are not
       met.

       A specific set of tools with which to initialize an environment when creating it may be
       specified using the optional keyword argument tools, which takes a list of tool names.
       This is useful to override the defaults, to specify non-default built-in tools, and to
       supply added tools:

           env = Environment(tools=['msvc', 'lex'])

       Tools can also be directly called by using the Tool method (see below).

       The tools argument overrides the default tool list, it does not add to it, so be sure to
       include all the tools you need. For example if you are building a c/c++ program you must
       specify a tool for at least a compiler and a linker, as in tools=['clang', 'link']. The
       tool name 'default' can be used to retain the default list.

       If no tools argument is specified, or if tools includes 'default', then scons will
       auto-detect usable tools, using the execution environment value of PATH (that is,
       env['ENV']['PATH'] - the external evironment PATH from os.environ is not used) for looking
       up any backing programs, and the platform name in effect to determine the default tools
       for that platform. Changing the PATH variable after the construction environment is
       constructed will not cause the tools to be re-detected.

       Additional tools can be added, see the Extending SCons section and specifically Tool
       Modules.

       SCons supports the following tool specifications out of the box:

       386asm
           Sets construction variables for the 386ASM assembler for the Phar Lap ETS embedded
           operating system.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $CC, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.

       aixc++
           Sets construction variables for the IMB xlc / Visual Age C++ compiler.

           Sets: $CXX, $CXXVERSION, $SHCXX, $SHOBJSUFFIX.

       aixcc
           Sets construction variables for the IBM xlc / Visual Age C compiler.

           Sets: $CC, $CCVERSION, $SHCC.

       aixf77
           Sets construction variables for the IBM Visual Age f77 Fortran compiler.

           Sets: $F77, $SHF77.

       aixlink
           Sets construction variables for the IBM Visual Age linker.

           Sets: $LINKFLAGS, $SHLIBSUFFIX, $SHLINKFLAGS.

       applelink
           Sets construction variables for the Apple linker (similar to the GNU linker).

           Sets: $APPLELINK_COMPATIBILITY_VERSION, $APPLELINK_CURRENT_VERSION,
           $APPLELINK_NO_COMPATIBILITY_VERSION, $APPLELINK_NO_CURRENT_VERSION,
           $FRAMEWORKPATHPREFIX, $LDMODULECOM, $LDMODULEFLAGS, $LDMODULEPREFIX, $LDMODULESUFFIX,
           $LINKCOM, $SHLINKCOM, $SHLINKFLAGS, $_APPLELINK_COMPATIBILITY_VERSION,
           $_APPLELINK_CURRENT_VERSION, $_FRAMEWORKPATH, $_FRAMEWORKS.

           Uses: $FRAMEWORKSFLAGS.

       ar
           Sets construction variables for the ar library archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX, $RANLIB, $RANLIBCOM,
           $RANLIBFLAGS.

       as
           Sets construction variables for the as assembler.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $CC, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.

       bcc32
           Sets construction variables for the bcc32 compiler.

           Sets: $CC, $CCCOM, $CCFLAGS, $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX, $CPPDEFSUFFIX,
           $INCPREFIX, $INCSUFFIX, $SHCC, $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHOBJSUFFIX.

           Uses: $_CPPDEFFLAGS, $_CPPINCFLAGS.

       cc
           Sets construction variables for generic POSIX C compilers.

           Sets: $CC, $CCCOM, $CCDEPFLAGS, $CCFLAGS, $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX,
           $CPPDEFSUFFIX, $FRAMEWORKPATH, $FRAMEWORKS, $INCPREFIX, $INCSUFFIX, $SHCC, $SHCCCOM,
           $SHCCFLAGS, $SHCFLAGS, $SHOBJSUFFIX.

           Uses: $CCCOMSTR, $PLATFORM, $SHCCCOMSTR.

       clang
           Set construction variables for the Clang C compiler.

           Sets: $CC, $CCDEPFLAGS, $CCVERSION, $SHCCFLAGS.

       clangxx
           Set construction variables for the Clang C++ compiler.

           Sets: $CXX, $CXXVERSION, $SHCXXFLAGS, $SHOBJSUFFIX,
           $STATIC_AND_SHARED_OBJECTS_ARE_THE_SAME.

       compilation_db
           Sets up CompilationDatabase builder which generates a clang tooling compatible
           compilation database.

           Sets: $COMPILATIONDB_COMSTR, $COMPILATIONDB_PATH_FILTER, $COMPILATIONDB_USE_ABSPATH.

       cvf
           Sets construction variables for the Compaq Visual Fortran compiler.

           Sets: $FORTRAN, $FORTRANCOM, $FORTRANMODDIR, $FORTRANMODDIRPREFIX,
           $FORTRANMODDIRSUFFIX, $FORTRANPPCOM, $OBJSUFFIX, $SHFORTRANCOM, $SHFORTRANPPCOM.

           Uses: $CPPFLAGS, $FORTRANFLAGS, $SHFORTRANFLAGS, $_CPPDEFFLAGS, $_FORTRANINCFLAGS,
           $_FORTRANMODFLAG.

       cXX
           Sets construction variables for generic POSIX C++ compilers.

           Sets: $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM, $CXXFILESUFFIX, $CXXFLAGS,
           $INCPREFIX, $INCSUFFIX, $OBJSUFFIX, $SHCXX, $SHCXXCOM, $SHCXXFLAGS, $SHOBJSUFFIX.

           Uses: $CXXCOMSTR, $SHCXXCOMSTR.

       cyglink
           Set construction variables for cygwin linker/loader.

           Sets: $IMPLIBPREFIX, $IMPLIBSUFFIX, $LDMODULEVERSIONFLAGS, $LINKFLAGS, $RPATHPREFIX,
           $RPATHSUFFIX, $SHLIBPREFIX, $SHLIBSUFFIX, $SHLIBVERSIONFLAGS, $SHLINKCOM,
           $SHLINKFLAGS, $_LDMODULEVERSIONFLAGS, $_SHLIBVERSIONFLAGS.

       default
           Sets construction variables for a default list of Tool modules. Use default in the
           tools list to retain the original defaults, since the tools parameter is treated as a
           literal statement of the tools to be made available in that construction environment,
           not an addition.

           The list of tools selected by default is not static, but is dependent both on the
           platform and on the software installed on the platform. Some tools will not initialize
           if an underlying command is not found, and some tools are selected from a list of
           choices on a first-found basis. The finished tool list can be examined by inspecting
           the $TOOLS construction variable in the construction environment.

           On all platforms, the tools from the following list are selected if their respective
           conditions are met: filesystem;, wix, lex, yacc, rpcgen, swig, jar, javac, javah,
           rmic, dvipdf, dvips, gs, tex, latex, pdflatex, pdftex, tar, zip, textfile.

           On Linux systems, the default tools list selects (first-found): a C compiler from gcc,
           intelc, icc, cc; a C++ compiler from g++, intelc, icc, cXX; an assembler from gas,
           nasm, masm; a linker from gnulink, ilink; a Fortran compiler from gfortran, g77,
           ifort, ifl, f95, f90, f77; and a static archiver ar. It also selects all found from
           the list m4 rpm.

           On Windows systems, the default tools list selects (first-found): a C compiler from
           msvc, mingw, gcc, intelc, icl, icc, cc, bcc32; a C++ compiler from msvc, intelc, icc,
           g++, cXX, bcc32; an assembler from masm, nasm, gas, 386asm; a linker from mslink,
           gnulink, ilink, linkloc, ilink32; a Fortran compiler from gfortran, g77, ifl, cvf,
           f95, f90, fortran; and a static archiver from mslib, ar, tlib; It also selects all
           found from the list msvs, midl.

           On MacOS systems, the default tools list selects (first-found): a C compiler from gcc,
           cc; a C++ compiler from g++, cXX; an assembler as; a linker from applelink, gnulink; a
           Fortran compiler from gfortran, f95, f90, g77; and a static archiver ar. It also
           selects all found from the list m4, rpm.

           Default lists for other platforms can be found by examining the scons source code (see
           SCons/Tool/__init__.py).

       dmd
           Sets construction variables for D language compiler DMD.

           Sets: $DC, $DCOM, $DDEBUG, $DDEBUGPREFIX, $DDEBUGSUFFIX, $DFILESUFFIX, $DFLAGPREFIX,
           $DFLAGS, $DFLAGSUFFIX, $DINCPREFIX, $DINCSUFFIX, $DLIB, $DLIBCOM, $DLIBDIRPREFIX,
           $DLIBDIRSUFFIX, $DLIBFLAGPREFIX, $DLIBFLAGSUFFIX, $DLIBLINKPREFIX, $DLIBLINKSUFFIX,
           $DLINK, $DLINKCOM, $DLINKFLAGPREFIX, $DLINKFLAGS, $DLINKFLAGSUFFIX, $DPATH,
           $DRPATHPREFIX, $DRPATHSUFFIX, $DVERPREFIX, $DVERSIONS, $DVERSUFFIX, $SHDC, $SHDCOM,
           $SHDLIBVERSIONFLAGS, $SHDLINK, $SHDLINKCOM, $SHDLINKFLAGS.

       docbook
           This tool tries to make working with Docbook in SCons a little easier. It provides
           several toolchains for creating different output formats, like HTML or PDF. Contained
           in the package is a distribution of the Docbook XSL stylesheets as of version 1.76.1.
           As long as you don't specify your own stylesheets for customization, these official
           versions are picked as default...which should reduce the inevitable setup hassles for
           you.

           Implicit dependencies to images and XIncludes are detected automatically if you meet
           the HTML requirements. The additional stylesheet utils/xmldepend.xsl by Paul DuBois is
           used for this purpose.

           Note, that there is no support for XML catalog resolving offered! This tool calls the
           XSLT processors and PDF renderers with the stylesheets you specified, that's it. The
           rest lies in your hands and you still have to know what you're doing when resolving
           names via a catalog.

           For activating the tool "docbook", you have to add its name to the Environment
           constructor, like this

               env = Environment(tools=['docbook'])

           On its startup, the docbook tool tries to find a required xsltproc processor, and a
           PDF renderer, e.g.  fop. So make sure that these are added to your system's
           environment PATH and can be called directly without specifying their full path.

           For the most basic processing of Docbook to HTML, you need to have installed

           •   the Python lxml binding to libxml2, or

           •   a standalone XSLT processor, currently detected are xsltproc, saxon, saxon-xslt
               and xalan.

           Rendering to PDF requires you to have one of the applications fop or xep installed.

           Creating a HTML or PDF document is very simple and straightforward. Say

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual.html', 'manual.xml')
               env.DocbookPdf('manual.pdf', 'manual.xml')

           to get both outputs from your XML source manual.xml. As a shortcut, you can give the
           stem of the filenames alone, like this:

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual')
               env.DocbookPdf('manual')

           and get the same result. Target and source lists are also supported:

               env = Environment(tools=['docbook'])
               env.DocbookHtml(['manual.html','reference.html'], ['manual.xml','reference.xml'])

           or even

               env = Environment(tools=['docbook'])
               env.DocbookHtml(['manual','reference'])

               Important
               Whenever you leave out the list of sources, you may not specify a file extension!
               The Tool uses the given names as file stems, and adds the suffixes for target and
               source files accordingly.
           The rules given above are valid for the Builders DocbookHtml, DocbookPdf, DocbookEpub,
           DocbookSlidesPdf and DocbookXInclude. For the DocbookMan transformation you can
           specify a target name, but the actual output names are automatically set from the
           refname entries in your XML source.

           The Builders DocbookHtmlChunked, DocbookHtmlhelp and DocbookSlidesHtml are special, in
           that:

            1. they create a large set of files, where the exact names and their number depend on
               the content of the source file, and

            2. the main target is always named index.html, i.e. the output name for the XSL
               transformation is not picked up by the stylesheets.

           As a result, there is simply no use in specifying a target HTML name. So the basic
           syntax for these builders is always:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('manual')

           If you want to use a specific XSL file, you can set the additional xsl parameter to
           your Builder call as follows:

               env.DocbookHtml('other.html', 'manual.xml', xsl='html.xsl')

           Since this may get tedious if you always use the same local naming for your customized
           XSL files, e.g.  html.xsl for HTML and pdf.xsl for PDF output, a set of variables for
           setting the default XSL name is provided. These are:

               DOCBOOK_DEFAULT_XSL_HTML
               DOCBOOK_DEFAULT_XSL_HTMLCHUNKED
               DOCBOOK_DEFAULT_XSL_HTMLHELP
               DOCBOOK_DEFAULT_XSL_PDF
               DOCBOOK_DEFAULT_XSL_EPUB
               DOCBOOK_DEFAULT_XSL_MAN
               DOCBOOK_DEFAULT_XSL_SLIDESPDF
               DOCBOOK_DEFAULT_XSL_SLIDESHTML

           and you can set them when constructing your environment:

               env = Environment(
                   tools=['docbook'],
                   DOCBOOK_DEFAULT_XSL_HTML='html.xsl',
                   DOCBOOK_DEFAULT_XSL_PDF='pdf.xsl',
               )
               env.DocbookHtml('manual')  # now uses html.xsl

           Sets: $DOCBOOK_DEFAULT_XSL_EPUB, $DOCBOOK_DEFAULT_XSL_HTML,
           $DOCBOOK_DEFAULT_XSL_HTMLCHUNKED, $DOCBOOK_DEFAULT_XSL_HTMLHELP,
           $DOCBOOK_DEFAULT_XSL_MAN, $DOCBOOK_DEFAULT_XSL_PDF, $DOCBOOK_DEFAULT_XSL_SLIDESHTML,
           $DOCBOOK_DEFAULT_XSL_SLIDESPDF, $DOCBOOK_FOP, $DOCBOOK_FOPCOM, $DOCBOOK_FOPFLAGS,
           $DOCBOOK_XMLLINT, $DOCBOOK_XMLLINTCOM, $DOCBOOK_XMLLINTFLAGS, $DOCBOOK_XSLTPROC,
           $DOCBOOK_XSLTPROCCOM, $DOCBOOK_XSLTPROCFLAGS, $DOCBOOK_XSLTPROCPARAMS.

           Uses: $DOCBOOK_FOPCOMSTR, $DOCBOOK_XMLLINTCOMSTR, $DOCBOOK_XSLTPROCCOMSTR.

       dvi
           Attaches the DVI builder to the construction environment.

       dvipdf
           Sets construction variables for the dvipdf utility.

           Sets: $DVIPDF, $DVIPDFCOM, $DVIPDFFLAGS.

           Uses: $DVIPDFCOMSTR.

       dvips
           Sets construction variables for the dvips utility.

           Sets: $DVIPS, $DVIPSFLAGS, $PSCOM, $PSPREFIX, $PSSUFFIX.

           Uses: $PSCOMSTR.

       f03
           Set construction variables for generic POSIX Fortran 03 compilers.

           Sets: $F03, $F03COM, $F03FLAGS, $F03PPCOM, $SHF03, $SHF03COM, $SHF03FLAGS,
           $SHF03PPCOM, $_F03INCFLAGS.

           Uses: $F03COMSTR, $F03PPCOMSTR, $FORTRANCOMMONFLAGS, $SHF03COMSTR, $SHF03PPCOMSTR.

       f08
           Set construction variables for generic POSIX Fortran 08 compilers.

           Sets: $F08, $F08COM, $F08FLAGS, $F08PPCOM, $SHF08, $SHF08COM, $SHF08FLAGS,
           $SHF08PPCOM, $_F08INCFLAGS.

           Uses: $F08COMSTR, $F08PPCOMSTR, $FORTRANCOMMONFLAGS, $SHF08COMSTR, $SHF08PPCOMSTR.

       f77
           Set construction variables for generic POSIX Fortran 77 compilers.

           Sets: $F77, $F77COM, $F77FILESUFFIXES, $F77FLAGS, $F77PPCOM, $F77PPFILESUFFIXES,
           $FORTRAN, $FORTRANCOM, $FORTRANFLAGS, $SHF77, $SHF77COM, $SHF77FLAGS, $SHF77PPCOM,
           $SHFORTRAN, $SHFORTRANCOM, $SHFORTRANFLAGS, $SHFORTRANPPCOM, $_F77INCFLAGS.

           Uses: $F77COMSTR, $F77PPCOMSTR, $FORTRANCOMMONFLAGS, $FORTRANCOMSTR, $FORTRANFLAGS,
           $FORTRANPPCOMSTR, $SHF77COMSTR, $SHF77PPCOMSTR, $SHFORTRANCOMSTR, $SHFORTRANFLAGS,
           $SHFORTRANPPCOMSTR.

       f90
           Set construction variables for generic POSIX Fortran 90 compilers.

           Sets: $F90, $F90COM, $F90FLAGS, $F90PPCOM, $SHF90, $SHF90COM, $SHF90FLAGS,
           $SHF90PPCOM, $_F90INCFLAGS.

           Uses: $F90COMSTR, $F90PPCOMSTR, $FORTRANCOMMONFLAGS, $SHF90COMSTR, $SHF90PPCOMSTR.

       f95
           Set construction variables for generic POSIX Fortran 95 compilers.

           Sets: $F95, $F95COM, $F95FLAGS, $F95PPCOM, $SHF95, $SHF95COM, $SHF95FLAGS,
           $SHF95PPCOM, $_F95INCFLAGS.

           Uses: $F95COMSTR, $F95PPCOMSTR, $FORTRANCOMMONFLAGS, $SHF95COMSTR, $SHF95PPCOMSTR.

       fortran
           Set construction variables for generic POSIX Fortran compilers.

           Sets: $FORTRAN, $FORTRANCOM, $FORTRANFLAGS, $SHFORTRAN, $SHFORTRANCOM,
           $SHFORTRANFLAGS, $SHFORTRANPPCOM.

           Uses: $CPPFLAGS, $FORTRANCOMSTR, $FORTRANPPCOMSTR, $SHFORTRANCOMSTR,
           $SHFORTRANPPCOMSTR, $_CPPDEFFLAGS.

       g++
           Set construction variables for the g++ C++ compiler.

           Sets: $CXX, $CXXVERSION, $SHCXXFLAGS, $SHOBJSUFFIX.

       g77
           Set construction variables for the g77 Fortran compiler.

           Sets: $F77, $F77COM, $F77FILESUFFIXES, $F77PPCOM, $F77PPFILESUFFIXES, $FORTRAN,
           $FORTRANCOM, $FORTRANPPCOM, $SHF77, $SHF77COM, $SHF77FLAGS, $SHF77PPCOM, $SHFORTRAN,
           $SHFORTRANCOM, $SHFORTRANFLAGS, $SHFORTRANPPCOM.

           Uses: $F77FLAGS, $FORTRANCOMMONFLAGS, $FORTRANFLAGS.

       gas
           Sets construction variables for the gas assembler. Calls the as tool.

           Sets: $AS.

       gcc
           Set construction variables for the gcc C compiler.

           Sets: $CC, $CCDEPFLAGS, $CCVERSION, $SHCCFLAGS.

       gdc
           Sets construction variables for the D language compiler GDC.

           Sets: $DC, $DCOM, $DDEBUG, $DDEBUGPREFIX, $DDEBUGSUFFIX, $DFILESUFFIX, $DFLAGPREFIX,
           $DFLAGS, $DFLAGSUFFIX, $DINCPREFIX, $DINCSUFFIX, $DLIB, $DLIBCOM, $DLIBDIRPREFIX,
           $DLIBDIRSUFFIX, $DLIBFLAGPREFIX, $DLIBFLAGSUFFIX, $DLIBLINKPREFIX, $DLIBLINKSUFFIX,
           $DLINK, $DLINKCOM, $DLINKFLAGPREFIX, $DLINKFLAGS, $DLINKFLAGSUFFIX, $DPATH,
           $DRPATHPREFIX, $DRPATHSUFFIX, $DVERPREFIX, $DVERSIONS, $DVERSUFFIX, $SHDC, $SHDCOM,
           $SHDLIBVERSIONFLAGS, $SHDLINK, $SHDLINKCOM, $SHDLINKFLAGS.

       gettext
           This is actually a toolset, which supports internationalization and localization of
           software being constructed with SCons. The toolset loads following tools:

           •    xgettext - to extract internationalized messages from source code to POT file(s),

           •    msginit - may be optionally used to initialize PO files,

           •    msgmerge - to update PO files, that already contain translated messages,

           •    msgfmt - to compile textual PO file to binary installable MO file.

           When you enable gettext, it internally loads all abovementioned tools, so you're
           encouraged to see their individual documentation.

           Each of the above tools provides its own builder(s) which may be used to perform
           particular activities related to software internationalization. You may be however
           interested in top-level Translate builder.

           To use gettext tools add 'gettext' tool to your environment:

                 env = Environment( tools = ['default', 'gettext'] )

       gfortran
           Sets construction variables for the GNU Fortran compiler. Calls the fortran Tool
           module to set variables.

           Sets: $F77, $F90, $F95, $FORTRAN, $SHF77, $SHF77FLAGS, $SHF90, $SHF90FLAGS, $SHF95,
           $SHF95FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.

       gnulink
           Set construction variables for GNU linker/loader.

           Sets: $LDMODULEVERSIONFLAGS, $RPATHPREFIX, $RPATHSUFFIX, $SHLIBVERSIONFLAGS,
           $SHLINKFLAGS, $_LDMODULESONAME, $_SHLIBSONAME.

       gs
           This Tool sets the required construction variables for working with the Ghostscript
           software. It also registers an appropriate Action with the PDF Builder, such that the
           conversion from PS/EPS to PDF happens automatically for the TeX/LaTeX toolchain.
           Finally, it adds an explicit Gs Builder for Ghostscript to the environment.

           Sets: $GS, $GSCOM, $GSFLAGS.

           Uses: $GSCOMSTR.

       hpc++
           Set construction variables for the compilers aCC on HP/UX systems.

       hpcc
           Set construction variables for aCC compilers on HP/UX systems. Calls the cXX tool for
           additional variables.

           Sets: $CXX, $CXXVERSION, $SHCXXFLAGS.

       hplink
           Sets construction variables for the linker on HP/UX systems.

           Sets: $LINKFLAGS, $SHLIBSUFFIX, $SHLINKFLAGS.

       icc
           Sets construction variables for the icc compiler on OS/2 systems.

           Sets: $CC, $CCCOM, $CFILESUFFIX, $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXXCOM,
           $CXXFILESUFFIX, $INCPREFIX, $INCSUFFIX.

           Uses: $CCFLAGS, $CFLAGS, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.

       icl
           Sets construction variables for the Intel C/C++ compiler. Calls the intelc Tool module
           to set its variables.

       ifl
           Sets construction variables for the Intel Fortran compiler.

           Sets: $FORTRAN, $FORTRANCOM, $FORTRANPPCOM, $SHFORTRANCOM, $SHFORTRANPPCOM.

           Uses: $CPPFLAGS, $FORTRANFLAGS, $_CPPDEFFLAGS, $_FORTRANINCFLAGS.

       ifort
           Sets construction variables for newer versions of the Intel Fortran compiler for
           Linux.

           Sets: $F77, $F90, $F95, $FORTRAN, $SHF77, $SHF77FLAGS, $SHF90, $SHF90FLAGS, $SHF95,
           $SHF95FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.

       ilink
           Sets construction variables for the ilink linker on OS/2 systems.

           Sets: $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM,
           $LINKFLAGS.

       ilink32
           Sets construction variables for the Borland ilink32 linker.

           Sets: $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM,
           $LINKFLAGS.

       install
           Sets construction variables for file and directory installation.

           Sets: $INSTALL, $INSTALLSTR.

       intelc
           Sets construction variables for the Intel C/C++ compiler (Linux and Windows, version 7
           and later). Calls the gcc or msvc (on Linux and Windows, respectively) tool to set
           underlying variables.

           Sets: $AR, $CC, $CXX, $INTEL_C_COMPILER_VERSION, $LINK.

       jar
           Sets construction variables for the jar utility.

           Sets: $JAR, $JARCOM, $JARFLAGS, $JARSUFFIX.

           Uses: $JARCOMSTR.

       javac
           Sets construction variables for the javac compiler.

           Sets: $JAVABOOTCLASSPATH, $JAVAC, $JAVACCOM, $JAVACFLAGS, $JAVACLASSPATH,
           $JAVACLASSSUFFIX, $JAVAINCLUDES, $JAVASOURCEPATH, $JAVASUFFIX.

           Uses: $JAVACCOMSTR.

       javah
           Sets construction variables for the javah tool.

           Sets: $JAVACLASSSUFFIX, $JAVAH, $JAVAHCOM, $JAVAHFLAGS.

           Uses: $JAVACLASSPATH, $JAVAHCOMSTR.

       latex
           Sets construction variables for the latex utility.

           Sets: $LATEX, $LATEXCOM, $LATEXFLAGS.

           Uses: $LATEXCOMSTR.

       ldc
           Sets construction variables for the D language compiler LDC2.

           Sets: $DC, $DCOM, $DDEBUG, $DDEBUGPREFIX, $DDEBUGSUFFIX, $DFILESUFFIX, $DFLAGPREFIX,
           $DFLAGS, $DFLAGSUFFIX, $DINCPREFIX, $DINCSUFFIX, $DLIB, $DLIBCOM, $DLIBDIRPREFIX,
           $DLIBDIRSUFFIX, $DLIBFLAGPREFIX, $DLIBFLAGSUFFIX, $DLIBLINKPREFIX, $DLIBLINKSUFFIX,
           $DLINK, $DLINKCOM, $DLINKFLAGPREFIX, $DLINKFLAGS, $DLINKFLAGSUFFIX, $DPATH,
           $DRPATHPREFIX, $DRPATHSUFFIX, $DVERPREFIX, $DVERSIONS, $DVERSUFFIX, $SHDC, $SHDCOM,
           $SHDLIBVERSIONFLAGS, $SHDLINK, $SHDLINKCOM, $SHDLINKFLAGS.

       lex
           Sets construction variables for the lex lexical analyser.

           Sets: $LEX, $LEXCOM, $LEXFLAGS, $LEXUNISTD.

           Uses: $LEXCOMSTR, $LEXFLAGS, $LEX_HEADER_FILE, $LEX_TABLES_FILE.

       link
           Sets construction variables for generic POSIX linkers. This is a "smart" linker tool
           which selects a compiler to complete the linking based on the types of source files.

           Sets: $LDMODULE, $LDMODULECOM, $LDMODULEFLAGS, $LDMODULENOVERSIONSYMLINKS,
           $LDMODULEPREFIX, $LDMODULESUFFIX, $LDMODULEVERSION, $LDMODULEVERSIONFLAGS,
           $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM,
           $LINKFLAGS, $SHLIBSUFFIX, $SHLINK, $SHLINKCOM, $SHLINKFLAGS, $__LDMODULEVERSIONFLAGS,
           $__SHLIBVERSIONFLAGS.

           Uses: $LDMODULECOMSTR, $LINKCOMSTR, $SHLINKCOMSTR.

       linkloc
           Sets construction variables for the LinkLoc linker for the Phar Lap ETS embedded
           operating system.

           Sets: $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM,
           $LINKFLAGS, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.

           Uses: $LINKCOMSTR, $SHLINKCOMSTR.

       m4
           Sets construction variables for the m4 macro processor.

           Sets: $M4, $M4COM, $M4FLAGS.

           Uses: $M4COMSTR.

       masm
           Sets construction variables for the Microsoft assembler.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $ASCOMSTR, $ASPPCOMSTR, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.

       midl
           Sets construction variables for the Microsoft IDL compiler.

           Sets: $MIDL, $MIDLCOM, $MIDLFLAGS.

           Uses: $MIDLCOMSTR.

       mingw
           Sets construction variables for MinGW (Minimal Gnu on Windows).

           Sets: $AS, $CC, $CXX, $LDMODULECOM, $LIBPREFIX, $LIBSUFFIX, $OBJSUFFIX, $RC, $RCCOM,
           $RCFLAGS, $RCINCFLAGS, $RCINCPREFIX, $RCINCSUFFIX, $SHCCFLAGS, $SHCXXFLAGS,
           $SHLINKCOM, $SHLINKFLAGS, $SHOBJSUFFIX, $WINDOWSDEFPREFIX, $WINDOWSDEFSUFFIX.

           Uses: $RCCOMSTR, $SHLINKCOMSTR.

       msgfmt
           This scons tool is a part of scons gettext toolset. It provides scons interface to
           msgfmt(1) command, which generates binary message catalog (MO) from a textual
           translation description (PO).

           Sets: $MOSUFFIX, $MSGFMT, $MSGFMTCOM, $MSGFMTCOMSTR, $MSGFMTFLAGS, $POSUFFIX.

           Uses: $LINGUAS_FILE.

       msginit
           This scons tool is a part of scons gettext toolset. It provides scons interface to
           msginit(1) program, which creates new PO file, initializing the meta information with
           values from user's environment (or options).

           Sets: $MSGINIT, $MSGINITCOM, $MSGINITCOMSTR, $MSGINITFLAGS, $POAUTOINIT,
           $POCREATE_ALIAS, $POSUFFIX, $POTSUFFIX, $_MSGINITLOCALE.

           Uses: $LINGUAS_FILE, $POAUTOINIT, $POTDOMAIN.

       msgmerge
           This scons tool is a part of scons gettext toolset. It provides scons interface to
           msgmerge(1) command, which merges two Uniform style .po files together.

           Sets: $MSGMERGE, $MSGMERGECOM, $MSGMERGECOMSTR, $MSGMERGEFLAGS, $POSUFFIX, $POTSUFFIX,
           $POUPDATE_ALIAS.

           Uses: $LINGUAS_FILE, $POAUTOINIT, $POTDOMAIN.

       mslib
           Sets construction variables for the Microsoft mslib library archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.

           Uses: $ARCOMSTR.

       mslink
           Sets construction variables for the Microsoft linker.

           Sets: $LDMODULE, $LDMODULECOM, $LDMODULEFLAGS, $LDMODULEPREFIX, $LDMODULESUFFIX,
           $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM,
           $LINKFLAGS, $REGSVR, $REGSVRCOM, $REGSVRFLAGS, $SHLINK, $SHLINKCOM, $SHLINKFLAGS,
           $WINDOWSDEFPREFIX, $WINDOWSDEFSUFFIX, $WINDOWSEXPPREFIX, $WINDOWSEXPSUFFIX,
           $WINDOWSPROGMANIFESTPREFIX, $WINDOWSPROGMANIFESTSUFFIX, $WINDOWSSHLIBMANIFESTPREFIX,
           $WINDOWSSHLIBMANIFESTSUFFIX, $WINDOWS_INSERT_DEF.

           Uses: $LDMODULECOMSTR, $LINKCOMSTR, $REGSVRCOMSTR, $SHLINKCOMSTR.

       mssdk
           Sets variables for Microsoft Platform SDK and/or Windows SDK. Note that unlike most
           other Tool modules, mssdk does not set construction variables, but sets the
           environment variables in the environment SCons uses to execute the Microsoft
           toolchain: %INCLUDE%, %LIB%, %LIBPATH% and %PATH%.

           Uses: $MSSDK_DIR, $MSSDK_VERSION, $MSVS_VERSION.

       msvc
           Sets construction variables for the Microsoft Visual C/C++ compiler.

           Sets: $BUILDERS, $CC, $CCCOM, $CCDEPFLAGS, $CCFLAGS, $CCPCHFLAGS, $CCPDBFLAGS,
           $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM, $CXXFILESUFFIX,
           $CXXFLAGS, $INCPREFIX, $INCSUFFIX, $OBJPREFIX, $OBJSUFFIX, $PCHCOM, $PCHPDBFLAGS, $RC,
           $RCCOM, $RCFLAGS, $SHCC, $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHCXX, $SHCXXCOM,
           $SHCXXFLAGS, $SHOBJPREFIX, $SHOBJSUFFIX.

           Uses: $CCCOMSTR, $CXXCOMSTR, $MSVC_NOTFOUND_POLICY, $MSVC_SCRIPTERROR_POLICY,
           $MSVC_SCRIPT_ARGS, $MSVC_SDK_VERSION, $MSVC_SPECTRE_LIBS, $MSVC_TOOLSET_VERSION,
           $MSVC_USE_SCRIPT, $MSVC_USE_SCRIPT_ARGS, $MSVC_USE_SETTINGS, $MSVC_VERSION, $PCH,
           $PCHSTOP, $PDB, $SHCCCOMSTR, $SHCXXCOMSTR.

       msvs
           Sets construction variables for Microsoft Visual Studio.

           Sets: $MSVSBUILDCOM, $MSVSCLEANCOM, $MSVSENCODING, $MSVSPROJECTCOM, $MSVSREBUILDCOM,
           $MSVSSCONS, $MSVSSCONSCOM, $MSVSSCONSCRIPT, $MSVSSCONSFLAGS, $MSVSSOLUTIONCOM.

       mwcc
           Sets construction variables for the Metrowerks CodeWarrior compiler.

           Sets: $CC, $CCCOM, $CFILESUFFIX, $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM,
           $CXXFILESUFFIX, $INCPREFIX, $INCSUFFIX, $MWCW_VERSION, $MWCW_VERSIONS, $SHCC,
           $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHCXX, $SHCXXCOM, $SHCXXFLAGS.

           Uses: $CCCOMSTR, $CXXCOMSTR, $SHCCCOMSTR, $SHCXXCOMSTR.

       mwld
           Sets construction variables for the Metrowerks CodeWarrior linker.

           Sets: $AR, $ARCOM, $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX,
           $LINK, $LINKCOM, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.

       nasm
           Sets construction variables for the nasm Netwide Assembler.

           Sets: $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.

           Uses: $ASCOMSTR, $ASPPCOMSTR.

       ninja
           Sets up the Ninja builder, which generates a ninja build file, and then optionally
           runs ninja.

               Note
               This is an experimental feature. This functionality is subject to change and/or
               removal without a deprecation cycle.
           Sets: $IMPLICIT_COMMAND_DEPENDENCIES, $NINJA_ALIAS_NAME, $NINJA_CMD_ARGS,
           $NINJA_COMPDB_EXPAND, $NINJA_DEPFILE_PARSE_FORMAT, $NINJA_DIR,
           $NINJA_DISABLE_AUTO_RUN, $NINJA_ENV_VAR_CACHE, $NINJA_FILE_NAME,
           $NINJA_FORCE_SCONS_BUILD, $NINJA_GENERATED_SOURCE_ALIAS_NAME,
           $NINJA_GENERATED_SOURCE_SUFFIXES, $NINJA_MSVC_DEPS_PREFIX, $NINJA_POOL,
           $NINJA_REGENERATE_DEPS, $NINJA_SCONS_DAEMON_KEEP_ALIVE, $NINJA_SCONS_DAEMON_PORT,
           $NINJA_SYNTAX, $_NINJA_REGENERATE_DEPS_FUNC.

           Uses: $AR, $ARCOM, $ARFLAGS, $CC, $CCCOM, $CCDEPFLAGS, $CCFLAGS, $CXX, $CXXCOM,
           $ESCAPE, $LINK, $LINKCOM, $PLATFORM, $PRINT_CMD_LINE_FUNC, $PROGSUFFIX, $RANLIB,
           $RANLIBCOM, $SHCCCOM, $SHCXXCOM, $SHLINK, $SHLINKCOM.

       packaging
           Sets construction variables for the Package Builder. If this tool is enabled, the
           --package-type command-line option is also enabled.

       pdf
           Sets construction variables for the Portable Document Format builder.

           Sets: $PDFPREFIX, $PDFSUFFIX.

       pdflatex
           Sets construction variables for the pdflatex utility.

           Sets: $LATEXRETRIES, $PDFLATEX, $PDFLATEXCOM, $PDFLATEXFLAGS.

           Uses: $PDFLATEXCOMSTR.

       pdftex
           Sets construction variables for the pdftex utility.

           Sets: $LATEXRETRIES, $PDFLATEX, $PDFLATEXCOM, $PDFLATEXFLAGS, $PDFTEX, $PDFTEXCOM,
           $PDFTEXFLAGS.

           Uses: $PDFLATEXCOMSTR, $PDFTEXCOMSTR.

       python
           Loads the Python source scanner into the invoking environment. When loaded, the
           scanner will attempt to find implicit dependencies for any Python source files in the
           list of sources provided to an Action that uses this environment.

           Available since scons 4.0..

       qt
           Placeholder tool to alert anyone still using qt tools to switch to qt3 or newer tool.

       qt3
           Sets construction variables for building Qt3 applications.

               Note
               This tool is only suitable for building targeted to Qt3, which is obsolete (the
               tool is deprecated since 4.3, and was renamed to qt3 in 4.5.0. ). There are
               contributed tools for Qt4 and Qt5, see https://github.com/SCons/scons-contrib[1].
               Qt4 has also passed end of life for standard support (in Dec 2015).
           Note paths for these construction variables are assembled using the os.path.join
           method so they will have the appropriate separator at runtime, but are listed here in
           the various entries only with the '/' separator for simplicity.

           In addition, the construction variables $CPPPATH, $LIBPATH and $LIBS may be modified
           and the variables $PROGEMITTER, $SHLIBEMITTER and $LIBEMITTER are modified. Because
           the build-performance is affected when using this tool, you have to explicitly specify
           it at Environment creation:

               Environment(tools=['default','qt3'])

           The qt3 tool supports the following operations:

           Automatic moc file generation from header files.  You do not have to specify moc files
           explicitly, the tool does it for you. However, there are a few preconditions to do so:
           Your header file must have the same filebase as your implementation file and must stay
           in the same directory. It must have one of the suffixes .h, .hpp, .H, .hxx, .hh. You
           can turn off automatic moc file generation by setting $QT3_AUTOSCAN to False. See also
           the corresponding Moc Builder.

           Automatic moc file generation from C++ files.  As described in the Qt documentation,
           include the moc file at the end of the C++ file. Note that you have to include the
           file, which is generated by the transformation
           ${QT3_MOCCXXPREFIX}<basename>${QT3_MOCCXXSUFFIX}, by default <basename>.mo. A warning
           is generated after building the moc file if you do not include the correct file. If
           you are using VariantDir, you may need to specify duplicate=True. You can turn off
           automatic moc file generation by setting $QT3_AUTOSCAN to False. See also the
           corresponding Moc Builder.

           Automatic handling of .ui files.  The implementation files generated from .ui files
           are handled much the same as yacc or lex files. Each .ui file given as a source of
           Program, Library or SharedLibrary will generate three files: the declaration file, the
           implementation file and a moc file. Because there are also generated headers, you may
           need to specify duplicate=True in calls to VariantDir. See also the corresponding Uic
           Builder.

           Sets: $QT3DIR, $QT3_AUTOSCAN, $QT3_BINPATH, $QT3_CPPPATH, $QT3_LIB, $QT3_LIBPATH,
           $QT3_MOC, $QT3_MOCCXXPREFIX, $QT3_MOCCXXSUFFIX, $QT3_MOCFROMCXXCOM,
           $QT3_MOCFROMCXXFLAGS, $QT3_MOCFROMHCOM, $QT3_MOCFROMHFLAGS, $QT3_MOCHPREFIX,
           $QT3_MOCHSUFFIX, $QT3_UIC, $QT3_UICCOM, $QT3_UICDECLFLAGS, $QT3_UICDECLPREFIX,
           $QT3_UICDECLSUFFIX, $QT3_UICIMPLFLAGS, $QT3_UICIMPLPREFIX, $QT3_UICIMPLSUFFIX,
           $QT3_UISUFFIX.

           Uses: $QT3DIR.

       rmic
           Sets construction variables for the rmic utility.

           Sets: $JAVACLASSSUFFIX, $RMIC, $RMICCOM, $RMICFLAGS.

           Uses: $RMICCOMSTR.

       rpcgen
           Sets construction variables for building with RPCGEN.

           Sets: $RPCGEN, $RPCGENCLIENTFLAGS, $RPCGENFLAGS, $RPCGENHEADERFLAGS,
           $RPCGENSERVICEFLAGS, $RPCGENXDRFLAGS.

       sgiar
           Sets construction variables for the SGI library archiver.

           Sets: $AR, $ARCOMSTR, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX, $SHLINK, $SHLINKFLAGS.

           Uses: $ARCOMSTR, $SHLINKCOMSTR.

       sgic++
           Sets construction variables for the SGI C++ compiler.

           Sets: $CXX, $CXXFLAGS, $SHCXX, $SHOBJSUFFIX.

       sgicc
           Sets construction variables for the SGI C compiler.

           Sets: $CXX, $SHOBJSUFFIX.

       sgilink
           Sets construction variables for the SGI linker.

           Sets: $LINK, $RPATHPREFIX, $RPATHSUFFIX, $SHLINKFLAGS.

       sunar
           Sets construction variables for the Sun library archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.

           Uses: $ARCOMSTR.

       sunc++
           Sets construction variables for the Sun C++ compiler.

           Sets: $CXX, $CXXVERSION, $SHCXX, $SHCXXFLAGS, $SHOBJPREFIX, $SHOBJSUFFIX.

       suncc
           Sets construction variables for the Sun C compiler.

           Sets: $CXX, $SHCCFLAGS, $SHOBJPREFIX, $SHOBJSUFFIX.

       sunf77
           Set construction variables for the Sun f77 Fortran compiler.

           Sets: $F77, $FORTRAN, $SHF77, $SHF77FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.

       sunf90
           Set construction variables for the Sun f90 Fortran compiler.

           Sets: $F90, $FORTRAN, $SHF90, $SHF90FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.

       sunf95
           Set construction variables for the Sun f95 Fortran compiler.

           Sets: $F95, $FORTRAN, $SHF95, $SHF95FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.

       sunlink
           Sets construction variables for the Sun linker.

           Sets: $RPATHPREFIX, $RPATHSUFFIX, $SHLINKFLAGS.

       swig
           Sets construction variables for the SWIG interface compiler.

           Sets: $SWIG, $SWIGCFILESUFFIX, $SWIGCOM, $SWIGCXXFILESUFFIX, $SWIGDIRECTORSUFFIX,
           $SWIGFLAGS, $SWIGINCPREFIX, $SWIGINCSUFFIX, $SWIGPATH, $SWIGVERSION, $_SWIGINCFLAGS.

           Uses: $SWIGCOMSTR.

       tar
           Sets construction variables for the tar archiver.

           Sets: $TAR, $TARCOM, $TARFLAGS, $TARSUFFIX.

           Uses: $TARCOMSTR.

       tex
           Sets construction variables for the TeX formatter and typesetter.

           Sets: $BIBTEX, $BIBTEXCOM, $BIBTEXFLAGS, $LATEX, $LATEXCOM, $LATEXFLAGS, $MAKEINDEX,
           $MAKEINDEXCOM, $MAKEINDEXFLAGS, $TEX, $TEXCOM, $TEXFLAGS.

           Uses: $BIBTEXCOMSTR, $LATEXCOMSTR, $MAKEINDEXCOMSTR, $TEXCOMSTR.

       textfile
           Set construction variables for the Textfile and Substfile builders.

           Sets: $FILE_ENCODING, $LINESEPARATOR, $SUBSTFILEPREFIX, $SUBSTFILESUFFIX,
           $TEXTFILEPREFIX, $TEXTFILESUFFIX.

           Uses: $SUBST_DICT.

       tlib
           Sets construction variables for the Borlan tib library archiver.

           Sets: $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.

           Uses: $ARCOMSTR.

       xgettext
           This scons tool is a part of scons gettext toolset. It provides scons interface to
           xgettext(1) program, which extracts internationalized messages from source code. The
           tool provides POTUpdate builder to make PO Template files.

           Sets: $POTSUFFIX, $POTUPDATE_ALIAS, $XGETTEXTCOM, $XGETTEXTCOMSTR, $XGETTEXTFLAGS,
           $XGETTEXTFROM, $XGETTEXTFROMPREFIX, $XGETTEXTFROMSUFFIX, $XGETTEXTPATH,
           $XGETTEXTPATHPREFIX, $XGETTEXTPATHSUFFIX, $_XGETTEXTDOMAIN, $_XGETTEXTFROMFLAGS,
           $_XGETTEXTPATHFLAGS.

           Uses: $POTDOMAIN.

       yacc
           Sets construction variables for the yacc parse generator.

           Sets: $YACC, $YACCCOM, $YACCFLAGS, $YACCHFILESUFFIX, $YACCHXXFILESUFFIX,
           $YACCVCGFILESUFFIX.

           Uses: $YACCCOMSTR, $YACCFLAGS, $YACC_GRAPH_FILE, $YACC_HEADER_FILE.

       zip
           Sets construction variables for the zip archiver.

           Sets: $ZIP, $ZIPCOM, $ZIPCOMPRESSION, $ZIPFLAGS, $ZIPSUFFIX.

           Uses: $ZIPCOMSTR.

   Builder Methods
       You tell SCons what to build by calling Builders, functions which take particular
       action(s) to produce target(s) of a particular type (conventionally hinted at by the
       builder name, e.g.  Program) from the specified source files. A builder call is a
       declaration: SCons enters the specified relationship into its internal dependency node
       graph, and only later makes the decision on whether anything is actually built, since this
       depends on command-line options, target selection rules, and whether the target(s) are out
       of date with respect to the sources.

       SCons provides a number of builders, and you can also write your own (see Builder
       Objects). Builders are created dynamically at run-time, often (though not always) by tools
       which determine whether the external dependencies for the builder are satisfied, and which
       perform the necessary setup (see Tools). Builders are attached to a construction
       environment as methods. The available builder methods are registered as key-value pairs in
       the $BUILDERS attribute of the construction environment, so the available builders can be
       examined. This example displays them for debugging purposes:

           env = Environment()
           print("Builders:", list(env['BUILDERS']))

       Builder methods take two required arguments: target and source. The target and source
       arguments can be specified either as positional arguments, in which case target comes
       first, or as keyword arguments, using target= and source=. Although both arguments are
       nominally required, if there is a single source and the target can be inferred the target
       argument can be omitted (see below). Builder methods also take a variety of keyword
       arguments, described below.

       Because long lists of file names can lead to a lot of quoting in a builder call, SCons
       supplies a Split global function and a same-named environment method that splits a single
       string into a list, using strings of white-space characters as the delimiter (similar to
       the Python string split method, but succeeds even if the input isn't a string).

       The following are equivalent examples of calling the Program builder method:

           env.Program('bar', ['bar.c', 'foo.c'])
           env.Program('bar', Split('bar.c foo.c'))
           env.Program('bar', env.Split('bar.c foo.c'))
           env.Program(source=['bar.c', 'foo.c'], target='bar')
           env.Program(target='bar', source=Split('bar.c foo.c'))
           env.Program(target='bar', source=env.Split('bar.c foo.c'))
           env.Program('bar', source='bar.c foo.c'.split())

       Sources and targets can be specified as a scalar or as a list, composed of either strings
       or nodes (more on nodes below). When specifying path strings, Python follows the POSIX
       pathname convention: if a string begins with the operating system pathname separator (on
       Windows both the slash and backslash separator are accepted, and any leading drive
       specifier is ignored for the determination) it is considered an absolute path, otherwise
       it is a relative path. If the path string contains no separator characters, it is searched
       for as a file in the current directory. If it contains separator characters, the search
       follows down from the starting point, which is the top of the directory tree for an
       absolute path and the current directory for a relative path. The "current directory" in
       this context is the directory of the SConscript file currently being processed.

       SCons also recognizes a third way to specify path strings: if the string begins with the #
       character it is top-relative - it works like a relative path but the search follows down
       from the directory containing the top-level SConstruct rather than from the current
       directory. The # can optionally be followed by a pathname separator, which is ignored if
       found in that position. Top-relative paths only work in places where scons will interpret
       the path (see some examples below). To be used in other contexts the string will need to
       be converted to a relative or absolute path first.

       Examples:

           # The comments describing the targets that will be built
           # assume these calls are in a SConscript file in the
           # a subdirectory named "subdir".

           # Builds the program "subdir/foo" from "subdir/foo.c":
           env.Program('foo', 'foo.c')

           # Builds the program "/tmp/bar" from "subdir/bar.c":
           env.Program('/tmp/bar', 'bar.c')

           # An initial '#' or '#/' are equivalent; the following
           # calls build the programs "foo" and "bar" (in the
           # top-level SConstruct directory) from "subdir/foo.c" and
           # "subdir/bar.c", respectively:
           env.Program('#foo', 'foo.c')
           env.Program('#/bar', 'bar.c')

           # Builds the program "other/foo" (relative to the top-level
           # SConstruct directory) from "subdir/foo.c":
           env.Program('#other/foo', 'foo.c')

           # This will not work, only SCons interfaces understand '#',
           # os.path.exists is pure Python:
           if os.path.exists('#inc/foo.h'):
               env.Append(CPPPATH='#inc')

       When the target shares the same base name as the source and only the suffix varies, and if
       the builder method has a suffix defined for the target file type, then the target argument
       may be omitted completely, and scons will deduce the target file name from the source file
       name. The following examples all build the executable program bar (on POSIX systems) or
       bar.exe (on Windows systems) from the bar.c source file:

           env.Program(target='bar', source='bar.c')
           env.Program('bar', source='bar.c')
           env.Program(source='bar.c')
           env.Program('bar.c')

       The optional srcdir keyword argument specifies that all source file strings that are not
       absolute paths or top-relative paths shall be interpreted relative to the specified
       srcdir. The following example will build the build/prog (or build/prog.exe on Windows)
       program from the files src/f1.c and src/f2.c:

           env.Program('build/prog', ['f1.c', 'f2.c'], srcdir='src')

       The optional parse_flags keyword argument causes behavior similar to the env.MergeFlags
       method, where the argument value is broken into individual settings and merged into the
       appropriate construction variables.

           env.Program('hello', 'hello.c', parse_flags='-Iinclude -DEBUG -lm')

       This example adds 'include' to the $CPPPATH construction variable, 'EBUG' to $CPPDEFINES,
       and 'm' to $LIBS.

       The optional chdir keyword argument specifies that the Builder's action(s) should be
       executed after changing directory. If the chdir argument is a path string or a directory
       Node, scons will change to the specified directory. If the chdir is not a string or Node
       and evaluates true, then scons will change to the target file's directory.

           Warning
           Python only keeps one current directory location even if there are multiple threads.
           This means that use of the chdir argument will not work with the SCons -j option,
           because individual worker threads spawned by SCons interfere with each other when they
           start changing directory.

           # scons will change to the "sub" subdirectory
           # before executing the "cp" command.
           env.Command(
               target='sub/dir/foo.out',
               source='sub/dir/foo.in',
               action="cp dir/foo.in dir/foo.out",
               chdir='sub',
           )

           # Because chdir is not a string, scons will change to the
           # target's directory ("sub/dir") before executing the
           # "cp" command.
           env.Command('sub/dir/foo.out', 'sub/dir/foo.in', "cp foo.in foo.out", chdir=True)

       Note that SCons will not automatically modify its expansion of construction variables like
       $TARGET and $SOURCE when using the chdir keyword argument--that is, the expanded file
       names will still be relative to the top-level directory where the SConstruct was found,
       and consequently incorrect relative to the chdir directory. If you use the chdir keyword
       argument, you will typically need to supply a different command line using expansions like
       ${TARGET.file} and ${SOURCE.file} to use just the filename portion of the target and
       source.

       Keyword arguments that are not specifically recognized are treated as construction
       variable overrides, which replace or add those variables on a limited basis. These
       overrides will only be in effect when building the target of the builder call, and will
       not affect other parts of the build. For example, if you want to specify some libraries
       needed by just one program:

           env.Program('hello', 'hello.c', LIBS=['gl', 'glut'])

       or generate a shared library with a non-standard suffix:

           env.SharedLibrary(
               target='word',
               source='word.cpp',
               SHLIBSUFFIX='.ocx',
               LIBSUFFIXES=['.ocx'],
           )

       Note that both the $SHLIBSUFFIX and $LIBSUFFIXES construction variables must be set if you
       want scons to search automatically for dependencies on the non-standard library names; see
       the descriptions of these variables for more information.

       Although the builder methods defined by scons are, in fact, methods of a construction
       environment object, many may also be called without an explicit environment:

           Program('hello', 'hello.c')
           SharedLibrary('word', 'word.cpp')

       If called this way, the builder will internally use the Default Environment that consists
       of the tools and values that scons has determined are appropriate for the local system.

       Builder methods that can be called without an explicit environment (indicated in the
       listing of builders below without a leading env.) may be called from custom Python modules
       that you import into an SConscript file by adding the following to the Python module:

           from SCons.Script import *

       A builder may add additional targets beyond those requested if an attached Emitter chooses
       to do so (see the section called “Builder Objects” for more information.  $PROGEMITTER is
       an example). For example, the GNU linker takes a command-line argument -Map=mapfile, which
       causes it to produce a linker map file in addition to the executable file actually being
       linked. If the Program builder's emitter is configured to add this mapfile if the option
       is set, then two targets will be returned when you only provided for one.

       For this reason, builder methods always return a NodeList, a list-like object whose
       elements are Nodes. Nodes are the internal representation of build targets or sources (see
       the section called “Node Objects” for more information). The returned NodeList object can
       be passed to other builder methods as source(s) or to other SCons functions or methods
       where a path string would normally be accepted.

       For example, to add a specific preprocessor define when compiling one specific object file
       but not the others:

           bar_obj_list = env.StaticObject('bar.c', CPPDEFINES='-DBAR')
           env.Program("prog", ['foo.c', bar_obj_list, 'main.c'])

       Using a Node as in this example makes for a more portable build by avoiding having to
       specify a platform-specific object suffix when calling the Program builder method.

       The NodeList object is also convenient to pass to the Default function, for the same
       reason of avoiding a platform-specific name:

           tgt = env.Program("prog", ["foo.c", "bar.c", "main.c"])
           Default(tgt)

       Builder calls will automatically "flatten" lists passed as source and target, so they are
       free to contain elements which are themselves lists, such as bar_obj_list returned by the
       StaticObject call. If you need to manipulate a list of lists returned by builders directly
       in Python code, you can either build a new list by hand:

           foo = Object('foo.c')
           bar = Object('bar.c')
           objects = ['begin.o'] + foo + ['middle.o'] + bar + ['end.o']
           for obj in objects:
               print(str(obj))

       Or you can use the Flatten function supplied by SCons to create a list containing just the
       Nodes, which may be more convenient:

           foo = Object('foo.c')
           bar = Object('bar.c')
           objects = Flatten(['begin.o', foo, 'middle.o', bar, 'end.o'])
           for obj in objects:
               print(str(obj))

       Since builder calls return a list-like object, not an actual Python list, it is not
       appropriate to use the Python add operator (+ or +=) to append builder results to a Python
       list. Because the list and the object are different types, Python will not update the
       original list in place, but will instead create a new NodeList object containing the
       concatenation of the list elements and the builder results. This will cause problems for
       any other Python variables in your SCons configuration that still hold on to a reference
       to the original list. Instead, use the Python list extend method to make sure the list is
       updated in-place. Example:

           object_files = []

           # Do NOT use += here:
           #    object_files += Object('bar.c')
           #
           # It will not update the object_files list in place.
           #
           # Instead, use the list extend method:
           object_files.extend(Object('bar.c'))

       The path name for a Node's file may be used by passing the Node to Python's builtin str
       function:

           bar_obj_list = env.StaticObject('bar.c', CPPDEFINES='-DBAR')
           print("The path to bar_obj is:", str(bar_obj_list[0]))

       Note that because the Builder call returns a NodeList, you have to access the first
       element in the list (bar_obj_list[0] in the example) to get at the Node that actually
       represents the object file.

       When trying to handle errors that may occur in a builder method, consider that the
       corresponding Action is executed at a different time than the SConscript file statement
       calling the builder. It is not useful to wrap a builder call in a try block, since success
       in the builder call is not the same as the builder itself succeeding. If necessary, a
       Builder's Action should be coded to exit with a useful exception message indicating the
       problem in the SConscript files - programmatically recovering from build errors is rarely
       useful.

       The following builder methods are predefined in the SCons core software distribution.
       Depending on the setup of a particular construction environment and on the type and
       software installation status of the underlying system, not all builders may be available
       in that construction environment. Since the function calling signature is the same for all
       builders:

           Buildername(target, source, [key=val, ...])

       it is omitted in this listing for brevity.

       CFile(), env.CFile()
           Builds a C source file given a lex (.l) or yacc (.y) input file. The suffix specified
           by the $CFILESUFFIX construction variable (.c by default) is automatically added to
           the target if it is not already present. Example:

               # builds foo.c
               env.CFile(target = 'foo.c', source = 'foo.l')
               # builds bar.c
               env.CFile(target = 'bar', source = 'bar.y')

       Command(), env.Command()
           The Command "Builder" is actually a function that looks like a Builder, but takes a
           required third argument, which is the action to take to construct the target from the
           source, used for "one-off" builds where a full builder is not needed. Thus it does not
           follow the builder calling rules described at the start of this section. See instead
           the Command function description for the calling syntax and details.

       CompilationDatabase(), env.CompilationDatabase()

           CompilationDatabase is a special builder which adds a target to create a JSON
           formatted compilation database compatible with clang tooling (see the LLVM
           specification[2]). This database is suitable for consumption by various tools and
           editors who can use it to obtain build and dependency information which otherwise
           would be internal to SCons. The builder does not require any source files to be
           specified, rather it arranges to emit information about all of the C, C++ and
           assembler source/output pairs identified in the build that are not excluded by the
           optional filter $COMPILATIONDB_PATH_FILTER. The target is subject to the usual SCons
           target selection rules.

           If called with no arguments, the builder will default to a target name of
           compile_commands.json.

           If called with a single positional argument, scons will "deduce" the target name from
           that source argument, giving it the same name, and then ignore the source. This is the
           usual way to call the builder if a non-default target name is wanted.

           If called with either the target= or source= keyword arguments, the value of the
           argument is taken as the target name. If called with both, the target= value is used
           and source= is ignored. If called with multiple sources, the source list will be
           ignored, since there is no way to deduce what the intent was; in this case the default
           target name will be used.

               Note
               You must load the compilation_db tool prior to specifying any part of your build
               or some source/output files will not show up in the compilation database.
           Available since scons 4.0.

       CXXFile(), env.CXXFile()
           Builds a C++ source file given a lex (.ll) or yacc (.yy) input file. The suffix
           specified by the $CXXFILESUFFIX construction variable (.cc by default) is
           automatically added to the target if it is not already present. Example:

               # builds foo.cc
               env.CXXFile(target = 'foo.cc', source = 'foo.ll')
               # builds bar.cc
               env.CXXFile(target = 'bar', source = 'bar.yy')

       DocbookEpub(), env.DocbookEpub()
           A pseudo-Builder, providing a Docbook toolchain for EPUB output.

               env = Environment(tools=['docbook'])
               env.DocbookEpub('manual.epub', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookEpub('manual')

       DocbookHtml(), env.DocbookHtml()
           A pseudo-Builder, providing a Docbook toolchain for HTML output.

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual.html', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookHtml('manual')

       DocbookHtmlChunked(), env.DocbookHtmlChunked()
           A pseudo-Builder providing a Docbook toolchain for chunked HTML output. It supports
           the base.dir parameter. The chunkfast.xsl file (requires "EXSLT") is used as the
           default stylesheet. Basic syntax:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlChunked('manual')

           where manual.xml is the input file.

           If you use the root.filename parameter in your own stylesheets you have to specify the
           new target name. This ensures that the dependencies get correct, especially for the
           cleanup via “scons -c”:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlChunked('mymanual.html', 'manual', xsl='htmlchunk.xsl')

           Some basic support for the base.dir parameter is provided. You can add the base_dir
           keyword to your Builder call, and the given prefix gets prepended to all the created
           filenames:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlChunked('manual', xsl='htmlchunk.xsl', base_dir='output/')

           Make sure that you don't forget the trailing slash for the base folder, else your
           files get renamed only!

       DocbookHtmlhelp(), env.DocbookHtmlhelp()
           A pseudo-Builder, providing a Docbook toolchain for HTMLHELP output. Its basic syntax
           is:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('manual')

           where manual.xml is the input file.

           If you use the root.filename parameter in your own stylesheets you have to specify the
           new target name. This ensures that the dependencies get correct, especially for the
           cleanup via “scons -c”:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('mymanual.html', 'manual', xsl='htmlhelp.xsl')

           Some basic support for the base.dir parameter is provided. You can add the base_dir
           keyword to your Builder call, and the given prefix gets prepended to all the created
           filenames:

               env = Environment(tools=['docbook'])
               env.DocbookHtmlhelp('manual', xsl='htmlhelp.xsl', base_dir='output/')

           Make sure that you don't forget the trailing slash for the base folder, else your
           files get renamed only!

       DocbookMan(), env.DocbookMan()
           A pseudo-Builder, providing a Docbook toolchain for Man page output. Its basic syntax
           is:

               env = Environment(tools=['docbook'])
               env.DocbookMan('manual')

           where manual.xml is the input file. Note, that you can specify a target name, but the
           actual output names are automatically set from the refname entries in your XML source.

       DocbookPdf(), env.DocbookPdf()
           A pseudo-Builder, providing a Docbook toolchain for PDF output.

               env = Environment(tools=['docbook'])
               env.DocbookPdf('manual.pdf', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookPdf('manual')

       DocbookSlidesHtml(), env.DocbookSlidesHtml()
           A pseudo-Builder, providing a Docbook toolchain for HTML slides output.

               env = Environment(tools=['docbook'])
               env.DocbookSlidesHtml('manual')

           If you use the titlefoil.html parameter in your own stylesheets you have to give the
           new target name. This ensures that the dependencies get correct, especially for the
           cleanup via “scons -c”:

               env = Environment(tools=['docbook'])
               env.DocbookSlidesHtml('mymanual.html','manual', xsl='slideshtml.xsl')

           Some basic support for the base.dir parameter is provided. You can add the base_dir
           keyword to your Builder call, and the given prefix gets prepended to all the created
           filenames:

               env = Environment(tools=['docbook'])
               env.DocbookSlidesHtml('manual', xsl='slideshtml.xsl', base_dir='output/')

           Make sure that you don't forget the trailing slash for the base folder, else your
           files get renamed only!

       DocbookSlidesPdf(), env.DocbookSlidesPdf()
           A pseudo-Builder, providing a Docbook toolchain for PDF slides output.

               env = Environment(tools=['docbook'])
               env.DocbookSlidesPdf('manual.pdf', 'manual.xml')

           or simply

               env = Environment(tools=['docbook'])
               env.DocbookSlidesPdf('manual')

       DocbookXInclude(), env.DocbookXInclude()
           A pseudo-Builder, for resolving XIncludes in a separate processing step.

               env = Environment(tools=['docbook'])
               env.DocbookXInclude('manual_xincluded.xml', 'manual.xml')

       DocbookXslt(), env.DocbookXslt()
           A pseudo-Builder, applying a given XSL transformation to the input file.

               env = Environment(tools=['docbook'])
               env.DocbookXslt('manual_transformed.xml', 'manual.xml', xsl='transform.xslt')

           Note, that this builder requires the xsl parameter to be set.

       DVI(), env.DVI()
           Builds a .dvi file from a .tex, .ltx or .latex input file. If the source file suffix
           is .tex, scons will examine the contents of the file; if the string \documentclass or
           \documentstyle is found, the file is assumed to be a LaTeX file and the target is
           built by invoking the $LATEXCOM command line; otherwise, the $TEXCOM command line is
           used. If the file is a LaTeX file, the DVI builder method will also examine the
           contents of the .aux file and invoke the $BIBTEX command line if the string bibdata is
           found, start $MAKEINDEX to generate an index if a .ind file is found and will examine
           the contents .log file and re-run the $LATEXCOM command if the log file says it is
           necessary.

           The suffix .dvi (hard-coded within TeX itself) is automatically added to the target if
           it is not already present. Examples:

               # builds from aaa.tex
               env.DVI(target = 'aaa.dvi', source = 'aaa.tex')
               # builds bbb.dvi
               env.DVI(target = 'bbb', source = 'bbb.ltx')
               # builds from ccc.latex
               env.DVI(target = 'ccc.dvi', source = 'ccc.latex')

       Gs(), env.Gs()
           A Builder for explicitly calling the gs executable. Depending on the underlying OS,
           the different names gs, gsos2 and gswin32c are tried.

               env = Environment(tools=['gs'])
               env.Gs(
                   'cover.jpg',
                   'scons-scons.pdf',
                   GSFLAGS='-dNOPAUSE -dBATCH -sDEVICE=jpeg -dFirstPage=1 -dLastPage=1 -q',
               )

       Install(), env.Install()
           Installs one or more source files or directories in the specified target, which must
           be a directory. The names of the specified source files or directories remain the same
           within the destination directory. The sources may be given as a string or as a node
           returned by a builder.

               env.Install(target='/usr/local/bin', source=['foo', 'bar'])

           Note that if target paths chosen for the Install builder (and the related InstallAs
           and InstallVersionedLib builders) are outside the project tree, such as in the example
           above, they may not be selected for "building" by default, since in the absence of
           other instructions scons builds targets that are underneath the top directory (the
           directory that contains the SConstruct file, usually the current directory). Use
           command line targets or the Default function in this case.

           If the --install-sandbox command line option is given, the target directory will be
           prefixed by the directory path specified. This is useful to test installs without
           installing to a "live" location in the system.

           See also FindInstalledFiles. For more thoughts on installation, see the User Guide
           (particularly the section on Command-Line Targets and the chapters on Installing Files
           and on Alias Targets).

       InstallAs(), env.InstallAs()
           Installs one or more source files or directories to specific names, allowing changing
           a file or directory name as part of the installation. It is an error if the target and
           source arguments list different numbers of files or directories.

               env.InstallAs(target='/usr/local/bin/foo',
                             source='foo_debug')
               env.InstallAs(target=['../lib/libfoo.a', '../lib/libbar.a'],
                             source=['libFOO.a', 'libBAR.a'])

           See the note under Install.

       InstallVersionedLib(), env.InstallVersionedLib()
           Installs a versioned shared library. The symlinks appropriate to the architecture will
           be generated based on symlinks of the source library.

               env.InstallVersionedLib(target='/usr/local/bin/foo',
                                       source='libxyz.1.5.2.so')

           See the note under Install.

       Jar(), env.Jar()
           Builds a Java archive (.jar) file from the specified list of sources. Any directories
           in the source list will be searched for .class files). Any .java files in the source
           list will be compiled to .class files by calling the Java Builder.

           If the $JARCHDIR value is set, the jar command will change to the specified directory
           using the -C option. If $JARCHDIR is not set explicitly, SCons will use the top of any
           subdirectory tree in which Java .class were built by the Java Builder.

           If the contents any of the source files begin with the string Manifest-Version, the
           file is assumed to be a manifest and is passed to the jar command with the m option
           set.

               env.Jar(target = 'foo.jar', source = 'classes')

               env.Jar(target = 'bar.jar',
                       source = ['bar1.java', 'bar2.java'])

       Java(), env.Java()
           Builds one or more Java class files. The sources may be any combination of explicit
           .java files, or directory trees which will be scanned for .java files.

           SCons will parse each source .java file to find the classes (including inner classes)
           defined within that file, and from that figure out the target .class files that will
           be created. The class files will be placed underneath the specified target directory.

           SCons will also search each Java file for the Java package name, which it assumes can
           be found on a line beginning with the string package in the first column; the
           resulting .class files will be placed in a directory reflecting the specified package
           name. For example, the file Foo.java defining a single public Foo class and containing
           a package name of sub.dir will generate a corresponding sub/dir/Foo.class class file.

           Examples:

               env.Java(target='classes', source='src')
               env.Java(target='classes', source=['src1', 'src2'])
               env.Java(target='classes', source=['File1.java', 'File2.java'])

           Java source files can use the native encoding for the underlying OS. Since SCons
           compiles in simple ASCII mode by default, the compiler will generate warnings about
           unmappable characters, which may lead to errors as the file is processed further. In
           this case, the user must specify the LANG environment variable to tell the compiler
           what encoding is used. For portibility, it's best if the encoding is hard-coded so
           that the compile will work if it is done on a system with a different encoding.

               env = Environment()
               env['ENV']['LANG'] = 'en_GB.UTF-8'

       JavaH(), env.JavaH()
           Builds C header and source files for implementing Java native methods. The target can
           be either a directory in which the header files will be written, or a header file name
           which will contain all of the definitions. The source can be the names of .class
           files, the names of .java files to be compiled into .class files by calling the Java
           builder method, or the objects returned from the Java builder method.

           If the construction variable $JAVACLASSDIR is set, either in the environment or in the
           call to the JavaH builder method itself, then the value of the variable will be
           stripped from the beginning of any .class file names.

           Examples:

               # builds java_native.h
               classes = env.Java(target="classdir", source="src")
               env.JavaH(target="java_native.h", source=classes)

               # builds include/package_foo.h and include/package_bar.h
               env.JavaH(target="include", source=["package/foo.class", "package/bar.class"])

               # builds export/foo.h and export/bar.h
               env.JavaH(
                   target="export",
                   source=["classes/foo.class", "classes/bar.class"],
                   JAVACLASSDIR="classes",
               )

               Note
               Java versions starting with 10.0 no longer use the javah command for generating
               JNI headers/sources, and indeed have removed the command entirely (see Java
               Enhancement Proposal JEP 313[3]), making this tool harder to use for that purpose.
               SCons may autodiscover a javah belonging to an older release if there are multiple
               Java versions on the system, which will lead to incorrect results. To use with a
               newer Java, override the default values of $JAVAH (to contain the path to the
               javac) and $JAVAHFLAGS (to contain at least a -h flag) and note that generating
               headers with javac requires supplying source .java files only, not .class files.

       Library(), env.Library()
           A synonym for the StaticLibrary builder method.

       LoadableModule(), env.LoadableModule()
           On most systems, this is the same as SharedLibrary. On Mac OS X (Darwin) platforms,
           this creates a loadable module bundle.

       M4(), env.M4()
           Builds an output file from an M4 input file. This uses a default $M4FLAGS value of -E,
           which considers all warnings to be fatal and stops on the first warning when using the
           GNU version of m4. Example:

               env.M4(target = 'foo.c', source = 'foo.c.m4')

       Moc(), env.Moc()
           Builds an output file from a moc input file.  moc input files are either header files
           or C++ files. This builder is only available after using the tool qt3. See the $QT3DIR
           variable for more information. Example:

               env.Moc('foo.h')  # generates moc_foo.cc
               env.Moc('foo.cpp')  # generates foo.moc

       MOFiles(), env.MOFiles()
           This builder belongs to msgfmt tool. The builder compiles PO files to MO files.

           Example 1. Create pl.mo and en.mo by compiling pl.po and en.po:

                 # ...
                 env.MOFiles(['pl', 'en'])

           Example 2. Compile files for languages defined in LINGUAS file:

                 # ...
                 env.MOFiles(LINGUAS_FILE = 1)

           Example 3. Create pl.mo and en.mo by compiling pl.po and en.po plus files for
           languages defined in LINGUAS file:

                 # ...
                 env.MOFiles(['pl', 'en'], LINGUAS_FILE = 1)

           Example 4. Compile files for languages defined in LINGUAS file (another version):

                 # ...
                 env['LINGUAS_FILE'] = 1
                 env.MOFiles()

       MSVSProject(), env.MSVSProject()
           Build a Microsoft Visual C++ project file and solution file.

           Builds a C++ project file based on the version of Visual Studio (or to be more
           precise, of MSBuild) that is configured: either the latest installed version, or the
           version specified by $MSVC_VERSION in the current construction environment. For Visual
           Studio 6.0 a .dsp file is generated. For Visual Studio versions 2002-2008, a .vcproj
           file is generated. For Visual Studio 2010 and later a .vcxproj file is generated. Note
           there are multiple versioning schemes involved in the Microsoft compilation
           environment - see the description of $MSVC_VERSION for equivalences.  SCons does not
           know how to construct project files for other languages (such as .csproj for C#,
           .vbproj for Visual Basic or .pyproject for Python)).

           For the .vcxproj file, the underlying format is the MSBuild XML Schema, and the
           details conform to:
           https://learn.microsoft.com/en-us/cpp/build/reference/vcxproj-file-structure[4]. The
           generated solution file enables Visual Studio to understand the project structure, and
           allows building it using MSBuild to call back to SCons. The project file encodes a
           toolset version that has been selected by SCons as described above. Since recent
           Visual Studio versions support multiple concurrent toolsets, use $MSVC_VERSION to
           select the desired one if it does not match the SCons default. The project file also
           includes entries which describe how to call SCons to build the project from within
           Visual Studio (or from an MSBuild command line). In some situations SCons may generate
           this incorrectly - notably when using the scons-local distribution, which is not
           installed in a way that that matches the default invocation line. If so, the
           $SCONS_HOME construction variable can be used to describe the right way to locate the
           SCons code so that it can be imported.

           By default, a matching solution file for the project is also generated. This behavior
           may be disabled by specifying auto_build_solution=0 to the MSVSProject builder. The
           solution file can also be independently generated by calling the MSVSSolution builder,
           such as in the case where a solution should describe multiple projects. See the
           MSVSSolution description for further information.

           The MSVSProject builder accepts several keyword arguments describing lists of
           filenames to be placed into the project file. Currently, srcs, incs, localincs,
           resources, and misc are recognized. The names are intended to be self-explanatory, but
           note that the filenames need to be specified as strings, not as SCons File Nodes (for
           example if you generate files for inclusion by using the Glob function, the results
           should be converted to a list of strings before passing them to MSVSProject). This is
           because Visual Studio and MSBuild know nothing about SCons Node types. Each of the
           filename lists are individually optional, but at least one list must be specified for
           the resulting project file to be non-empty.

           In addition to the above lists of values, the following values may be specified as
           keyword arguments:

           target
               The name of the target .dsp or .vcproj file. The correct suffix for the version of
               Visual Studio must be used, but the $MSVSPROJECTSUFFIX construction variable will
               be defined to the correct value (see example below).

           variant
               The name of this particular variant. Except for Visual Studio 6 projects, this can
               also be a list of variant names. These are typically things like "Debug" or
               "Release", but really can be anything you want. For Visual Studio 7 projects, they
               may also specify a target platform separated from the variant name by a |
               (vertical pipe) character: Debug|Xbox. The default target platform is Win32.
               Multiple calls to MSVSProject with different variants are allowed; all variants
               will be added to the project file with their appropriate build targets and
               sources.

           cmdargs
               Additional command line arguments for the different variants. The number of
               cmdargs entries must match the number of variant entries, or be empty (not
               specified). If you give only one, it will automatically be propagated to all
               variants.

           cppdefines
               Preprocessor definitions for the different variants. The number of cppdefines
               entries must match the number of variant entries, or be empty (not specified). If
               you give only one, it will automatically be propagated to all variants. If you
               don't give this parameter, SCons will use the invoking environment's $CPPDEFINES
               entry for all variants.

           cppflags
               Compiler flags for the different variants. If a /std:c++ flag is found then
               /Zc:__cplusplus is appended to the flags if not already found, this ensures that
               Intellisense uses the /std:c++ switch. The number of cppflags entries must match
               the number of variant entries, or be empty (not specified). If you give only one,
               it will automatically be propagated to all variants. If you don't give this
               parameter, SCons will combine the invoking environment's $CCFLAGS, $CXXFLAGS,
               $CPPFLAGS entries for all variants.

           cpppaths
               Compiler include paths for the different variants. The number of cpppaths entries
               must match the number of variant entries, or be empty (not specified). If you give
               only one, it will automatically be propagated to all variants. If you don't give
               this parameter, SCons will use the invoking environment's $CPPPATH entry for all
               variants.

           buildtarget
               An optional string, node, or list of strings or nodes (one per build variant), to
               tell the Visual Studio debugger what output target to use in what build variant.
               The number of buildtarget entries must match the number of variant entries.

           runfile
               The name of the file that Visual Studio 7 and later will run and debug. This
               appears as the value of the Output field in the resulting Visual C++ project file.
               If this is not specified, the default is the same as the specified buildtarget
               value.

               Note
               SCons and Microsoft Visual Studio understand projects in different ways, and the
               mapping is sometimes imperfect:

               Because SCons always executes its build commands from the directory in which the
               SConstruct file is located, if you generate a project file in a different
               directory than the directory of the SConstruct file, users will not be able to
               double-click on the file name in compilation error messages displayed in the
               Visual Studio console output window. This can be remedied by adding the Visual
               C/C++ /FC compiler option to the $CCFLAGS variable so that the compiler will print
               the full path name of any files that cause compilation errors.

               If the project file is only used to teach the Visual Studio project browser about
               the file layout there should be no issues, However, Visual Studio should not be
               used to make changes to the project structure, build options, etc. as these will
               (a) not feed back to the SCons description of the project and (b) be lost if SCons
               regenerates the project file. The SConscript files should remain the definitive
               description of the build.

               If the project file is used to drive MSBuild (such as selecting "build" from the
               Visual Studio interface) you lose the direct control of target selection and
               command-line options you would have if launching the build directly from SCons,
               because these will be hardcoded in the project file to the values specified in the
               MSVSProject call. You can regain some of this control by defining multiple
               variants, using multiple MSVSProject calls to arrange different build targets,
               arguments, defines, flags and paths for different variants.

               If the build is divided into a solution with multiple MSBuild projects the mapping
               is further strained. In this case, it is important not to set Visual Studio to do
               parallel builds, as it will then launch the separate project builds in parallel,
               and SCons does not work well if called that way. Instead you can set up the SCons
               build for parallel building - see the SetOption function for how to do this with
               num_jobs.
           Example usage:

               barsrcs = ['bar.cpp']
               barincs = ['bar.h']
               barlocalincs = ['StdAfx.h']
               barresources = ['bar.rc', 'resource.h']
               barmisc = ['bar_readme.txt']

               dll = env.SharedLibrary(target='bar.dll', source=barsrcs)
               buildtarget = [s for s in dll if str(s).endswith('dll')]
               env.MSVSProject(
                   target='Bar' + env['MSVSPROJECTSUFFIX'],
                   srcs=barsrcs,
                   incs=barincs,
                   localincs=barlocalincs,
                   resources=barresources,
                   misc=barmisc,
                   buildtarget=buildtarget,
                   variant='Release',
               )

           DebugSettings
               A dictionary of debug settings that get written to the .vcproj.user or the
               .vcxproj.user file, depending on the version installed. As for cmdargs, you can
               specify a DebugSettings dictionary per variant. If you give only one, it will be
               propagated to all variants.

               Changed in version 2.4: Added the optional DebugSettings parameter.

           Currently, only Visual Studio v9.0 and Visual Studio version v11 are implemented, for
           other versions no file is generated. To generate the user file, you just need to add a
           DebugSettings dictionary to the environment with the right parameters for your MSVS
           version. If the dictionary is empty, or does not contain any good value, no file will
           be generated.

           Following is a more contrived example, involving the setup of a project for variants
           and DebugSettings:

               # Assuming you store your defaults in a file
               vars = Variables('variables.py')
               msvcver = vars.args.get('vc', '9')

               # Check command args to force one Microsoft Visual Studio version
               if msvcver == '9' or msvcver == '11':
                   env = Environment(MSVC_VERSION=msvcver + '.0', MSVC_BATCH=False)
               else:
                   env = Environment()

               AddOption(
                   '--userfile',
                   action='store_true',
                   dest='userfile',
                   default=False,
                   help="Create Visual C++ project file",
               )

               #
               # 1. Configure your Debug Setting dictionary with options you want in the list
               # of allowed options, for instance if you want to create a user file to launch
               # a specific application for testing your dll with Microsoft Visual Studio 2008 (v9):
               #
               V9DebugSettings = {
                   'Command': 'c:\\myapp\\using\\thisdll.exe',
                   'WorkingDirectory': 'c:\\myapp\\using\\',
                   'CommandArguments': '-p password',
                   # 'Attach':'false',
                   # 'DebuggerType':'3',
                   # 'Remote':'1',
                   # 'RemoteMachine': None,
                   # 'RemoteCommand': None,
                   # 'HttpUrl': None,
                   # 'PDBPath': None,
                   # 'SQLDebugging': None,
                   # 'Environment': '',
                   # 'EnvironmentMerge':'true',
                   # 'DebuggerFlavor': None,
                   # 'MPIRunCommand': None,
                   # 'MPIRunArguments': None,
                   # 'MPIRunWorkingDirectory': None,
                   # 'ApplicationCommand': None,
                   # 'ApplicationArguments': None,
                   # 'ShimCommand': None,
                   # 'MPIAcceptMode': None,
                   # 'MPIAcceptFilter': None,
               }

               #
               # 2. Because there are a lot of different options depending on the Microsoft
               # Visual Studio version, if you use more than one version you have to
               # define a dictionary per version, for instance if you want to create a user
               # file to launch a specific application for testing your dll with Microsoft
               # Visual Studio 2012 (v11):
               #
               V10DebugSettings = {
                   'LocalDebuggerCommand': 'c:\\myapp\\using\\thisdll.exe',
                   'LocalDebuggerWorkingDirectory': 'c:\\myapp\\using\\',
                   'LocalDebuggerCommandArguments': '-p password',
                   # 'LocalDebuggerEnvironment': None,
                   # 'DebuggerFlavor': 'WindowsLocalDebugger',
                   # 'LocalDebuggerAttach': None,
                   # 'LocalDebuggerDebuggerType': None,
                   # 'LocalDebuggerMergeEnvironment': None,
                   # 'LocalDebuggerSQLDebugging': None,
                   # 'RemoteDebuggerCommand': None,
                   # 'RemoteDebuggerCommandArguments': None,
                   # 'RemoteDebuggerWorkingDirectory': None,
                   # 'RemoteDebuggerServerName': None,
                   # 'RemoteDebuggerConnection': None,
                   # 'RemoteDebuggerDebuggerType': None,
                   # 'RemoteDebuggerAttach': None,
                   # 'RemoteDebuggerSQLDebugging': None,
                   # 'DeploymentDirectory': None,
                   # 'AdditionalFiles': None,
                   # 'RemoteDebuggerDeployDebugCppRuntime': None,
                   # 'WebBrowserDebuggerHttpUrl': None,
                   # 'WebBrowserDebuggerDebuggerType': None,
                   # 'WebServiceDebuggerHttpUrl': None,
                   # 'WebServiceDebuggerDebuggerType': None,
                   # 'WebServiceDebuggerSQLDebugging': None,
               }

               #
               # 3. Select the dictionary you want depending on the version of visual Studio
               # Files you want to generate.
               #
               if not env.GetOption('userfile'):
                   dbgSettings = None
               elif env.get('MSVC_VERSION', None) == '9.0':
                   dbgSettings = V9DebugSettings
               elif env.get('MSVC_VERSION', None) == '11.0':
                   dbgSettings = V10DebugSettings
               else:
                   dbgSettings = None

               #
               # 4. Add the dictionary to the DebugSettings keyword.
               #
               barsrcs = ['bar.cpp', 'dllmain.cpp', 'stdafx.cpp']
               barincs = ['targetver.h']
               barlocalincs = ['StdAfx.h']
               barresources = ['bar.rc', 'resource.h']
               barmisc = ['ReadMe.txt']

               dll = env.SharedLibrary(target='bar.dll', source=barsrcs)

               env.MSVSProject(
                   target='Bar' + env['MSVSPROJECTSUFFIX'],
                   srcs=barsrcs,
                   incs=barincs,
                   localincs=barlocalincs,
                   resources=barresources,
                   misc=barmisc,
                   buildtarget=[dll[0]] * 2,
                   variant=('Debug|Win32', 'Release|Win32'),
                   cmdargs=f'vc={msvcver}',
                   DebugSettings=(dbgSettings, {}),
               )

       MSVSSolution(), env.MSVSSolution()
           Build a Microsoft Visual Studio Solution file.

           Builds a Visual Studio solution file based on the version of Visual Studio that is
           configured: either the latest installed version, or the version specified by
           $MSVC_VERSION in the construction environment. For Visual Studio 6, a .dsw file is
           generated. For Visual Studio .NET 2002 and later, it will generate a .sln file. Note
           there are multiple versioning schemes involved in the Microsoft compilation
           environment - see the description of $MSVC_VERSION for equivalences.

           The solution file is a container for one or more projects, and follows the format
           described at
           https://learn.microsoft.com/en-us/visualstudio/extensibility/internals/solution-dot-sln-file[5].

           The following values must be specified:

           target
               The name of the target .dsw or .sln file. The correct suffix for the version of
               Visual Studio must be used, but the value $MSVSSOLUTIONSUFFIX will be defined to
               the correct value (see example below).

           variant
               The name of this particular variant, or a list of variant names (the latter is
               only supported for MSVS 7 solutions). These are typically things like "Debug" or
               "Release", but really can be anything you want. For MSVS 7 they may also specify
               target platform, like this "Debug|Xbox". Default platform is Win32.

           projects
               A list of project file names, or Project nodes returned by calls to the
               MSVSProject Builder, to be placed into the solution file. Note that these
               filenames need to be specified as strings, NOT as SCons File Nodes. This is
               because the solution file will be interpreted by MSBuild and by Visual Studio,
               which know nothing about SCons Node types.

           Example Usage:

               env.MSVSSolution(
                   target="Bar" + env["MSVSSOLUTIONSUFFIX"],
                   projects=["bar" + env["MSVSPROJECTSUFFIX"]],
                   variant="Release",
               )

       Ninja(), env.Ninja()
           A special builder which adds a target to create a Ninja build file. The builder does
           not require any source files to be specified.

               Note
               This is an experimental feature. To enable it you must use one of the following
               methods

                   # On the command line
                   --experimental=ninja

                   # Or in your SConstruct
                   SetOption('experimental', 'ninja')

               This functionality is subject to change and/or removal without deprecation cycle.

               To use this tool you need to install the Python ninja package, as the tool by
               default depends on being able to do an import of the package This can be done via:

                   python -m pip install ninja

           If called with no arguments, the builder will default to a target name of ninja.build.

           If called with a single positional argument, scons will "deduce" the target name from
           that source argument, giving it the same name, and then ignore the source. This is the
           usual way to call the builder if a non-default target name is wanted.

           If called with either the target= or source= keyword arguments, the value of the
           argument is taken as the target name. If called with both, the target= value is used
           and source= is ignored. If called with multiple sources, the source list will be
           ignored, since there is no way to deduce what the intent was; in this case the default
           target name will be used.

           Available since scons 4.2.

       Object(), env.Object()
           A synonym for the StaticObject builder method.

       Package(), env.Package()
           Builds software distribution packages. A package is a container format which includes
           files to install along with metadata. Packaging is optional, and must be enabled by
           specifying the packaging tool. For example:

               env = Environment(tools=['default', 'packaging'])

           SCons can build packages in a number of well known packaging formats. The target
           package type may be selected with the the $PACKAGETYPE construction variable or the
           --package-type command line option. The package type may be a list, in which case
           SCons will attempt to build packages for each type in the list. Example:

               env.Package(PACKAGETYPE=['src_zip', 'src_targz'], ...other args...)

           The currently supported packagers are:

           ┌───────────┬─────────────────────────────────┐
           │msi        │ Microsoft Installer package     │
           ├───────────┼─────────────────────────────────┤
           │rpm        │ RPM Package Manger package      │
           ├───────────┼─────────────────────────────────┤
           │ipkg       │ Itsy Package Management package │
           ├───────────┼─────────────────────────────────┤
           │tarbz2     │ bzip2-compressed tar file       │
           ├───────────┼─────────────────────────────────┤
           │targz      │ gzip-compressed tar file        │
           ├───────────┼─────────────────────────────────┤
           │tarxz      │ xz-compressed tar file          │
           ├───────────┼─────────────────────────────────┤
           │zip        │ zip file                        │
           ├───────────┼─────────────────────────────────┤
           │src_tarbz2 │ bzip2-compressed tar file       │
           │           │ suitable as source to another   │
           │           │ packager                        │
           ├───────────┼─────────────────────────────────┤
           │src_targz  │ gzip-compressed tar file        │
           │           │ suitable as source to another   │
           │           │ packager                        │
           ├───────────┼─────────────────────────────────┤
           │src_tarxz  │ xz-compressed tar file suitable │
           │           │ as source to another packager   │
           ├───────────┼─────────────────────────────────┤
           │src_zip    │ zip file suitable as source to  │
           │           │ another packager                │
           └───────────┴─────────────────────────────────┘
           The file list to include in the package may be specified with the source keyword
           argument. If omitted, the FindInstalledFiles function is called behind the scenes to
           select all files that have an Install, InstallAs or InstallVersionedLib Builder
           attached. If the target keyword argument is omitted, the target name(s) will be
           deduced from the package type(s).

           The metadata comes partly from attributes of the files to be packaged, and partly from
           packaging tags. Tags can be passed as keyword arguments to the Package builder call,
           and may also be attached to files (or more accurately, Nodes representing files) with
           the Tag function. Some package-level tags are mandatory, and will lead to errors if
           omitted. The mandatory tags vary depending on the package type.

           While packaging, the builder uses a temporary location named by the value of the
           $PACKAGEROOT variable - the package sources are copied there before packaging.

           Packaging example:

               env = Environment(tools=["default", "packaging"])
               env.Install("/bin/", "my_program")
               env.Package(
                   NAME="foo",
                   VERSION="1.2.3",
                   PACKAGEVERSION=0,
                   PACKAGETYPE="rpm",
                   LICENSE="gpl",
                   SUMMARY="balalalalal",
                   DESCRIPTION="this should be really really long",
                   X_RPM_GROUP="Application/fu",
                   SOURCE_URL="https://foo.org/foo-1.2.3.tar.gz",
               )

           In this example, the target /bin/my_program created by the Install call would not be
           built by default since it is not under the project top directory. However, since no
           source is specified to the Package builder, it is selected for packaging by the
           default sources rule. Since packaging is done using $PACKAGEROOT, no write is actually
           done to the system's /bin directory, and the target will be selected since after
           rebasing to underneath $PACKAGEROOT it is now under the top directory of the project.

       PCH(), env.PCH()
           Builds a Microsoft Visual C++ precompiled header. Calling this builder returns a list
           of two targets: the PCH as the first element, and the object file as the second
           element. Normally the object file is ignored. This builder is only provided when
           Microsoft Visual C++ is being used as the compiler. The PCH builder is generally used
           in conjunction with the $PCH construction variable to force object files to use the
           precompiled header:

               env['PCH'] = env.PCH('StdAfx.cpp')[0]

       PDF(), env.PDF()
           Builds a .pdf file from a .dvi input file (or, by extension, a .tex, .ltx, or .latex
           input file). The suffix specified by the $PDFSUFFIX construction variable (.pdf by
           default) is added automatically to the target if it is not already present. Example:

               # builds from aaa.tex
               env.PDF(target = 'aaa.pdf', source = 'aaa.tex')
               # builds bbb.pdf from bbb.dvi
               env.PDF(target = 'bbb', source = 'bbb.dvi')

       POInit(), env.POInit()
           This builder belongs to msginit tool. The builder initializes missing PO file(s) if
           $POAUTOINIT is set. If $POAUTOINIT is not set (default), POInit prints instruction for
           user (that is supposed to be a translator), telling how the PO file should be
           initialized. In normal projects you should not use POInit and use POUpdate instead.
           POUpdate chooses intelligently between msgmerge(1) and msginit(1).  POInit always uses
           msginit(1) and should be regarded as builder for special purposes or for temporary use
           (e.g. for quick, one time initialization of a bunch of PO files) or for tests.

           Target nodes defined through POInit are not built by default (they're Ignored from '.'
           node) but are added to special Alias ('po-create' by default). The alias name may be
           changed through the $POCREATE_ALIAS construction variable. All PO files defined
           through POInit may be easily initialized by scons po-create.

           Example 1. Initialize en.po and pl.po from messages.pot:

                 # ...
                 env.POInit(['en', 'pl']) # messages.pot --> [en.po, pl.po]

           Example 2. Initialize en.po and pl.po from foo.pot:

                 # ...
                 env.POInit(['en', 'pl'], ['foo']) # foo.pot --> [en.po, pl.po]

           Example 3. Initialize en.po and pl.po from foo.pot but using $POTDOMAIN construction
           variable:

                 # ...
                 env.POInit(['en', 'pl'], POTDOMAIN='foo') # foo.pot --> [en.po, pl.po]

           Example 4. Initialize PO files for languages defined in LINGUAS file. The files will
           be initialized from template messages.pot:

                 # ...
                 env.POInit(LINGUAS_FILE = 1) # needs 'LINGUAS' file

           Example 5. Initialize en.po and pl.pl PO files plus files for languages defined in
           LINGUAS file. The files will be initialized from template messages.pot:

                 # ...
                 env.POInit(['en', 'pl'], LINGUAS_FILE = 1)

           Example 6. You may preconfigure your environment first, and then initialize PO files:

                 # ...
                 env['POAUTOINIT'] = 1
                 env['LINGUAS_FILE'] = 1
                 env['POTDOMAIN'] = 'foo'
                 env.POInit()

           which has same efect as:

                 # ...
                 env.POInit(POAUTOINIT = 1, LINGUAS_FILE = 1, POTDOMAIN = 'foo')

       PostScript(), env.PostScript()
           Builds a .ps file from a .dvi input file (or, by extension, a .tex, .ltx, or .latex
           input file). The suffix specified by the $PSSUFFIX construction variable (.ps by
           default) is added automatically to the target if it is not already present. Example:

               # builds from aaa.tex
               env.PostScript(target = 'aaa.ps', source = 'aaa.tex')
               # builds bbb.ps from bbb.dvi
               env.PostScript(target = 'bbb', source = 'bbb.dvi')

       POTUpdate(), env.POTUpdate()
           The builder belongs to xgettext tool. The builder updates target POT file if exists or
           creates one if it doesn't. The node is not built by default (i.e. it is Ignored from
           '.'), but only on demand (i.e. when given POT file is required or when special alias
           is invoked). This builder adds its targe node (messages.pot, say) to a special alias
           (pot-update by default, see $POTUPDATE_ALIAS) so you can update/create them easily
           with scons pot-update. The file is not written until there is no real change in
           internationalized messages (or in comments that enter POT file).

               Note
               You may see xgettext(1) being invoked by the xgettext tool even if there is no
               real change in internationalized messages (so the POT file is not being updated).
               This happens every time a source file has changed. In such case we invoke
               xgettext(1) and compare its output with the content of POT file to decide whether
               the file should be updated or not.

           Example 1.  Let's create po/ directory and place following SConstruct script there:

                 # SConstruct in 'po/' subdir
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(['foo'], ['../a.cpp', '../b.cpp'])
                 env.POTUpdate(['bar'], ['../c.cpp', '../d.cpp'])

           Then invoke scons few times:

                 user@host:$ scons             # Does not create foo.pot nor bar.pot
                 user@host:$ scons foo.pot     # Updates or creates foo.pot
                 user@host:$ scons pot-update  # Updates or creates foo.pot and bar.pot
                 user@host:$ scons -c          # Does not clean foo.pot nor bar.pot.

           the results shall be as the comments above say.

           Example 2.  The POTUpdate builder may be used with no target specified, in which case
           default target messages.pot will be used. The default target may also be overridden by
           setting $POTDOMAIN construction variable or providing it as an override to POTUpdate
           builder:

                 # SConstruct script
                 env = Environment( tools = ['default', 'xgettext'] )
                 env['POTDOMAIN'] = "foo"
                 env.POTUpdate(source = ["a.cpp", "b.cpp"]) # Creates foo.pot ...
                 env.POTUpdate(POTDOMAIN = "bar", source = ["c.cpp", "d.cpp"]) # and bar.pot

           Example 3.  The sources may be specified within separate file, for example
           POTFILES.in:

                 # POTFILES.in in 'po/' subdirectory
                 ../a.cpp
                 ../b.cpp
                 # end of file

           The name of the file (POTFILES.in) containing the list of sources is provided via
           $XGETTEXTFROM:

                 # SConstruct file in 'po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in')

           Example 4.  You may use $XGETTEXTPATH to define source search path. Assume, for
           example, that you have files a.cpp, b.cpp, po/SConstruct, po/POTFILES.in. Then your
           POT-related files could look as below:

                 # POTFILES.in in 'po/' subdirectory
                 a.cpp
                 b.cpp
                 # end of file

                 # SConstruct file in 'po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH='../')

           Example 5.  Multiple search directories may be defined within a list, i.e.
           XGETTEXTPATH = ['dir1', 'dir2', ...]. The order in the list determines the search
           order of source files. The path to the first file found is used.

           Let's create 0/1/po/SConstruct script:

                 # SConstruct file in '0/1/po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH=['../', '../../'])

           and 0/1/po/POTFILES.in:

                 # POTFILES.in in '0/1/po/' subdirectory
                 a.cpp
                 # end of file

           Write two *.cpp files, the first one is 0/a.cpp:

                 /* 0/a.cpp */
                 gettext("Hello from ../../a.cpp")

           and the second is 0/1/a.cpp:

                 /* 0/1/a.cpp */
                 gettext("Hello from ../a.cpp")

           then run scons. You'll obtain 0/1/po/messages.pot with the message "Hello from
           ../a.cpp". When you reverse order in $XGETTEXTFOM, i.e. when you write SConscript as

                 # SConstruct file in '0/1/po/' subdirectory
                 env = Environment( tools = ['default', 'xgettext'] )
                 env.POTUpdate(XGETTEXTFROM = 'POTFILES.in', XGETTEXTPATH=['../../', '../'])

           then the messages.pot will contain msgid "Hello from ../../a.cpp" line and not msgid
           "Hello from ../a.cpp".

       POUpdate(), env.POUpdate()
           The builder belongs to msgmerge tool. The builder updates PO files with msgmerge(1),
           or initializes missing PO files as described in documentation of msginit tool and
           POInit builder (see also $POAUTOINIT). Note, that POUpdate does not add its targets to
           po-create alias as POInit does.

           Target nodes defined through POUpdate are not built by default (they're Ignored from
           '.' node). Instead, they are added automatically to special Alias ('po-update' by
           default). The alias name may be changed through the $POUPDATE_ALIAS construction
           variable. You can easily update PO files in your project by scons po-update.

           Example 1.  Update en.po and pl.po from messages.pot template (see also $POTDOMAIN),
           assuming that the later one exists or there is rule to build it (see POTUpdate):

                 # ...
                 env.POUpdate(['en','pl']) # messages.pot --> [en.po, pl.po]

           Example 2.  Update en.po and pl.po from foo.pot template:

                 # ...
                 env.POUpdate(['en', 'pl'], ['foo']) # foo.pot -->  [en.po, pl.pl]

           Example 3.  Update en.po and pl.po from foo.pot (another version):

                 # ...
                 env.POUpdate(['en', 'pl'], POTDOMAIN='foo') # foo.pot -- > [en.po, pl.pl]

           Example 4.  Update files for languages defined in LINGUAS file. The files are updated
           from messages.pot template:

                 # ...
                 env.POUpdate(LINGUAS_FILE = 1) # needs 'LINGUAS' file

           Example 5.  Same as above, but update from foo.pot template:

                 # ...
                 env.POUpdate(LINGUAS_FILE = 1, source = ['foo'])

           Example 6.  Update en.po and pl.po plus files for languages defined in LINGUAS file.
           The files are updated from messages.pot template:

                 # produce 'en.po', 'pl.po' + files defined in 'LINGUAS':
                 env.POUpdate(['en', 'pl' ], LINGUAS_FILE = 1)

           Example 7.  Use $POAUTOINIT to automatically initialize PO file if it doesn't exist:

                 # ...
                 env.POUpdate(LINGUAS_FILE = 1, POAUTOINIT = 1)

           Example 8.  Update PO files for languages defined in LINGUAS file. The files are
           updated from foo.pot template. All necessary settings are pre-configured via
           environment.

                 # ...
                 env['POAUTOINIT'] = 1
                 env['LINGUAS_FILE'] = 1
                 env['POTDOMAIN'] = 'foo'
                 env.POUpdate()

       Program(), env.Program()
           Builds an executable given one or more object files or C, C++, D, or Fortran source
           files. If any C, C++, D or Fortran source files are specified, then they will be
           automatically compiled to object files using the Object builder method; see that
           builder method's description for a list of legal source file suffixes and how they are
           interpreted. The target executable file prefix, specified by the $PROGPREFIX
           construction variable (nothing by default), and suffix, specified by the $PROGSUFFIX
           construction variable (by default, .exe on Windows systems, nothing on POSIX systems),
           are automatically added to the target if not already present. Example:

               env.Program(target='foo', source=['foo.o', 'bar.c', 'baz.f'])

       ProgramAllAtOnce(), env.ProgramAllAtOnce()
           Builds an executable from D sources without first creating individual objects for each
           file.

           D sources can be compiled file-by-file as C and C++ source are, and D is integrated
           into the scons Object and Program builders for this model of build. D codes can though
           do whole source meta-programming (some of the testing frameworks do this). For this it
           is imperative that all sources are compiled and linked in a single call to the D
           compiler. This builder serves that purpose.

                   env.ProgramAllAtOnce('executable', ['mod_a.d, mod_b.d', 'mod_c.d'])

           This command will compile the modules mod_a, mod_b, and mod_c in a single compilation
           process without first creating object files for the modules. Some of the D compilers
           will create executable.o others will not.

       RES(), env.RES()
           Builds a Microsoft Visual C++ resource file. This builder method is only provided when
           Microsoft Visual C++ or MinGW is being used as the compiler. The .res (or .o for
           MinGW) suffix is added to the target name if no other suffix is given. The source file
           is scanned for implicit dependencies as though it were a C file. Example:

               env.RES('resource.rc')

       RMIC(), env.RMIC()
           Builds stub and skeleton class files for remote objects from Java .class files. The
           target is a directory relative to which the stub and skeleton class files will be
           written. The source can be the names of .class files, or the objects return from the
           Java builder method.

           If the construction variable $JAVACLASSDIR is set, either in the environment or in the
           call to the RMIC builder method itself, then the value of the variable will be
           stripped from the beginning of any .class file names.

               classes = env.Java(target='classdir', source='src')
               env.RMIC(target='outdir1', source=classes)
               env.RMIC(
                   target='outdir2',
                   source=['package/foo.class', 'package/bar.class'],
               )
               env.RMIC(
                   target='outdir3',
                   source=['classes/foo.class', 'classes/bar.class'],
                   JAVACLASSDIR='classes',
               )

       RPCGenClient(), env.RPCGenClient()
           Generates an RPC client stub (_clnt.c) file from a specified RPC (.x) source file.
           Because rpcgen only builds output files in the local directory, the command will be
           executed in the source file's directory by default.

               # Builds src/rpcif_clnt.c
               env.RPCGenClient('src/rpcif.x')

       RPCGenHeader(), env.RPCGenHeader()
           Generates an RPC header (.h) file from a specified RPC (.x) source file. Because
           rpcgen only builds output files in the local directory, the command will be executed
           in the source file's directory by default.

               # Builds src/rpcif.h
               env.RPCGenHeader('src/rpcif.x')

       RPCGenService(), env.RPCGenService()
           Generates an RPC server-skeleton (_svc.c) file from a specified RPC (.x) source file.
           Because rpcgen only builds output files in the local directory, the command will be
           executed in the source file's directory by default.

               # Builds src/rpcif_svc.c
               env.RPCGenClient('src/rpcif.x')

       RPCGenXDR(), env.RPCGenXDR()
           Generates an RPC XDR routine (_xdr.c) file from a specified RPC (.x) source file.
           Because rpcgen only builds output files in the local directory, the command will be
           executed in the source file's directory by default.

               # Builds src/rpcif_xdr.c
               env.RPCGenClient('src/rpcif.x')

       SharedLibrary(), env.SharedLibrary()
           Builds a shared library (.so on a POSIX system, .dll on Windows) given one or more
           object files or C, C++, D or Fortran source files. If any source files are given, then
           they will be automatically compiled to object files. The target library file prefix,
           specified by the $SHLIBPREFIX construction variable (by default, lib on POSIX systems,
           nothing on Windows systems), and suffix, specified by the $SHLIBSUFFIX construction
           variable (by default, .dll on Windows systems, .so on POSIX systems), are
           automatically added to the target if not already present. Example:

               env.SharedLibrary(target='bar', source=['bar.c', 'foo.o'])

           On Windows systems, the SharedLibrary builder method will always build an import
           library (.lib) in addition to the shared library (.dll), adding a .lib library with
           the same basename if there is not already a .lib file explicitly listed in the
           targets.

           On Cygwin systems, the SharedLibrary builder method will always build an import
           library (.dll.a) in addition to the shared library (.dll), adding a .dll.a library
           with the same basename if there is not already a .dll.a file explicitly listed in the
           targets.

           Any object files listed in the source must have been built for a shared library (that
           is, using the SharedObject builder method).  scons will raise an error if there is any
           mismatch.

           On some platforms, there is a distinction between a shared library (loaded
           automatically by the system to resolve external references) and a loadable module
           (explicitly loaded by user action). For maximum portability, use the LoadableModule
           builder for the latter.

           When the $SHLIBVERSION construction variable is defined, a versioned shared library is
           created. This modifies $SHLINKFLAGS as required, adds the version number to the
           library name, and creates any symbolic links that are needed.

               env.SharedLibrary(target='bar', source=['bar.c', 'foo.o'], SHLIBVERSION='1.5.2')

           On a POSIX system, versions with a single token create exactly one symlink:
           libbar.so.6 would have symlink libbar.so only. On a POSIX system, versions with two or
           more tokens create exactly two symlinks: libbar.so.2.3.1 would have symlinks libbar.so
           and libbar.so.2; on a Darwin (OSX) system the library would be libbar.2.3.1.dylib and
           the link would be libbar.dylib.

           On Windows systems, specifying register=1 will cause the .dll to be registered after
           it is built. The command that is run is determined by the $REGSVR construction
           variable (regsvr32 by default), and the flags passed are determined by $REGSVRFLAGS.
           By default, $REGSVRFLAGS includes the /s option, to prevent dialogs from popping up
           and requiring user attention when it is run. If you change $REGSVRFLAGS, be sure to
           include the /s option. For example,

               env.SharedLibrary(target='bar', source=['bar.cxx', 'foo.obj'], register=1)

           will register bar.dll as a COM object when it is done linking it.

       SharedObject(), env.SharedObject()
           Builds an object file intended for inclusion in a shared library. Source files must
           have one of the same set of extensions specified above for the StaticObject builder
           method. On some platforms building a shared object requires additional compiler option
           (e.g.  -fPIC for gcc) in addition to those needed to build a normal (static) object,
           but on some platforms there is no difference between a shared object and a normal
           (static) one. When there is a difference, SCons will only allow shared objects to be
           linked into a shared library, and will use a different suffix for shared objects. On
           platforms where there is no difference, SCons will allow both normal (static) and
           shared objects to be linked into a shared library, and will use the same suffix for
           shared and normal (static) objects. The target object file prefix, specified by the
           $SHOBJPREFIX construction variable (by default, the same as $OBJPREFIX), and suffix,
           specified by the $SHOBJSUFFIX construction variable, are automatically added to the
           target if not already present. Examples:

               env.SharedObject(target='ddd', source='ddd.c')
               env.SharedObject(target='eee.o', source='eee.cpp')
               env.SharedObject(target='fff.obj', source='fff.for')

           Note that the source files will be scanned according to the suffix mappings in the
           SourceFileScanner object. See the manpage section "Scanner Objects" for more
           information.

       StaticLibrary(), env.StaticLibrary()
           Builds a static library given one or more object files or C, C++, D or Fortran source
           files. If any source files are given, then they will be automatically compiled to
           object files. The static library file prefix, specified by the $LIBPREFIX construction
           variable (by default, lib on POSIX systems, nothing on Windows systems), and suffix,
           specified by the $LIBSUFFIX construction variable (by default, .lib on Windows
           systems, .a on POSIX systems), are automatically added to the target if not already
           present. Example:

               env.StaticLibrary(target='bar', source=['bar.c', 'foo.o'])

           Any object files listed in the source must have been built for a static library (that
           is, using the StaticObject builder method).  scons will raise an error if there is any
           mismatch.

       StaticObject(), env.StaticObject()
           Builds a static object file from one or more C, C++, D, or Fortran source files.
           Source files must have one of the following extensions:

                 .asm    assembly language file
                 .ASM    assembly language file
                 .c      C file
                 .C      Windows:  C file
                         POSIX:  C++ file
                 .cc     C++ file
                 .cpp    C++ file
                 .cxx    C++ file
                 .cxx    C++ file
                 .c++    C++ file
                 .C++    C++ file
                 .d      D file
                 .f      Fortran file
                 .F      Windows:  Fortran file
                         POSIX:  Fortran file + C pre-processor
                 .for    Fortran file
                 .FOR    Fortran file
                 .fpp    Fortran file + C pre-processor
                 .FPP    Fortran file + C pre-processor
                 .m      Object C file
                 .mm     Object C++ file
                 .s      assembly language file
                 .S      Windows:  assembly language file
                         ARM: CodeSourcery Sourcery Lite
                 .sx     assembly language file + C pre-processor
                         POSIX:  assembly language file + C pre-processor
                 .spp    assembly language file + C pre-processor
                 .SPP    assembly language file + C pre-processor

           The target object file prefix, specified by the $OBJPREFIX construction variable
           (nothing by default), and suffix, specified by the $OBJSUFFIX construction variable
           (.obj on Windows systems, .o on POSIX systems), are automatically added to the target
           if not already present. Examples:

               env.StaticObject(target='aaa', source='aaa.c')
               env.StaticObject(target='bbb.o', source='bbb.c++')
               env.StaticObject(target='ccc.obj', source='ccc.f')

           Note that the source files will be scanned according to the suffix mappings in the
           SourceFileScanner object. See the manpage section "Scanner Objects" for more
           information.

       Substfile(), env.Substfile()
           The Substfile builder creates a single text file from a template consisting of a file
           or set of files (or nodes), replacing text using the $SUBST_DICT construction variable
           (if set). If a set, they are concatenated into the target file using the value of the
           $LINESEPARATOR construction variable as a separator between contents; the separator is
           not emitted after the contents of the last file. Nested lists of source files are
           flattened. See also Textfile.

           By default the target file encoding is "utf-8" and can be changed by $FILE_ENCODING
           Examples:

           If a single source file name is specified and has a .in suffix, the suffix is stripped
           and the remainder of the name is used as the default target name.

           The prefix and suffix specified by the $SUBSTFILEPREFIX and $SUBSTFILESUFFIX
           construction variables (an empty string by default in both cases) are automatically
           added to the target if they are not already present.

           If a construction variable named $SUBST_DICT is present, it may be either a Python
           dictionary or a sequence of (key, value) tuples. If it is a dictionary it is converted
           into a list of tuples with unspecified order, so if one key is a prefix of another key
           or if one substitution could be further expanded by another subsitition, it is
           unpredictable whether the expansion will occur.

           Any occurrences of a key in the source are replaced by the corresponding value, which
           may be a Python callable function or a string. If the value is a callable, it is
           called with no arguments to get a string. Strings are subst-expanded and the result
           replaces the key.

               env = Environment(tools=['default'])

               env['prefix'] = '/usr/bin'
               script_dict = {'@prefix@': '/bin', '@exec_prefix@': '$prefix'}
               env.Substfile('script.in', SUBST_DICT=script_dict)

               conf_dict = {'%VERSION%': '1.2.3', '%BASE%': 'MyProg'}
               env.Substfile('config.h.in', conf_dict, SUBST_DICT=conf_dict)

               # UNPREDICTABLE - one key is a prefix of another
               bad_foo = {'$foo': '$foo', '$foobar': '$foobar'}
               env.Substfile('foo.in', SUBST_DICT=bad_foo)

               # PREDICTABLE - keys are applied longest first
               good_foo = [('$foobar', '$foobar'), ('$foo', '$foo')]
               env.Substfile('foo.in', SUBST_DICT=good_foo)

               # UNPREDICTABLE - one substitution could be futher expanded
               bad_bar = {'@bar@': '@soap@', '@soap@': 'lye'}
               env.Substfile('bar.in', SUBST_DICT=bad_bar)

               # PREDICTABLE - substitutions are expanded in order
               good_bar = (('@bar@', '@soap@'), ('@soap@', 'lye'))
               env.Substfile('bar.in', SUBST_DICT=good_bar)

               # the SUBST_DICT may be in common (and not an override)
               substutions = {}
               subst = Environment(tools=['textfile'], SUBST_DICT=substitutions)
               substitutions['@foo@'] = 'foo'
               subst['SUBST_DICT']['@bar@'] = 'bar'
               subst.Substfile(
                   'pgm1.c',
                   [Value('#include "@foo@.h"'), Value('#include "@bar@.h"'), "common.in", "pgm1.in"],
               )
               subst.Substfile(
                   'pgm2.c',
                   [Value('#include "@foo@.h"'), Value('#include "@bar@.h"'), "common.in", "pgm2.in"],
               )

       Tar(), env.Tar()
           Builds a tar archive of the specified files and/or directories. Unlike most builder
           methods, the Tar builder method may be called multiple times for a given target; each
           additional call adds to the list of entries that will be built into the archive. Any
           source directories will be scanned for changes to any on-disk files, regardless of
           whether or not scons knows about them from other Builder or function calls.

               env.Tar('src.tar', 'src')

               # Create the stuff.tar file.
               env.Tar('stuff', ['subdir1', 'subdir2'])
               # Also add "another" to the stuff.tar file.
               env.Tar('stuff', 'another')

               # Set TARFLAGS to create a gzip-filtered archive.
               env = Environment(TARFLAGS = '-c -z')
               env.Tar('foo.tar.gz', 'foo')

               # Also set the suffix to .tgz.
               env = Environment(TARFLAGS = '-c -z',
                                 TARSUFFIX = '.tgz')
               env.Tar('foo')

       Textfile(), env.Textfile()
           The Textfile builder generates a single text file from a template consisting of a list
           of strings, replacing text using the $SUBST_DICT construction variable (if set) - see
           Substfile for a description of replacement. The strings will be separated in the
           target file using the value of the $LINESEPARATOR construction variable; the line
           separator is not emitted after the last string. Nested lists of source strings are
           flattened. Source strings need not literally be Python strings: they can be Nodes or
           Python objects that convert cleanly to Value nodes.

           The prefix and suffix specified by the $TEXTFILEPREFIX and $TEXTFILESUFFIX
           construction variables (by default an empty string and .txt, respectively) are
           automatically added to the target if they are not already present.

           By default the target file encoding is "utf-8" and can be changed by $FILE_ENCODING
           Examples:

               # builds/writes foo.txt
               env.Textfile(target='foo.txt', source=['Goethe', 42, 'Schiller'])

               # builds/writes bar.txt
               env.Textfile(target='bar', source=['lalala', 'tanteratei'], LINESEPARATOR='|*')

               # nested lists are flattened automatically
               env.Textfile(target='blob', source=['lalala', ['Goethe', 42, 'Schiller'], 'tanteratei'])

               # files may be used as input by wraping them in File()
               env.Textfile(
                   target='concat',  # concatenate files with a marker between
                   source=[File('concat1'), File('concat2')],
                   LINESEPARATOR='====================\n',
               )

           Results:

           foo.txt

                 Goethe
                 42
                 Schiller

           bar.txt

                 lalala|*tanteratei

           blob.txt

                 lalala
                 Goethe
                 42
                 Schiller
                 tanteratei

       Translate(), env.Translate()
           This pseudo-builder belongs to gettext toolset. The builder extracts internationalized
           messages from source files, updates POT template (if necessary) and then updates PO
           translations (if necessary). If $POAUTOINIT is set, missing PO files will be
           automatically created (i.e. without translator person intervention). The variables
           $LINGUAS_FILE and $POTDOMAIN are taken into acount too. All other construction
           variables used by POTUpdate, and POUpdate work here too.

           Example 1. The simplest way is to specify input files and output languages inline in a
           SCons script when invoking Translate

               # SConscript in 'po/' directory
               env = Environment( tools = ["default", "gettext"] )
               env['POAUTOINIT'] = 1
               env.Translate(['en','pl'], ['../a.cpp','../b.cpp'])

           Example 2. If you wish, you may also stick to conventional style known from autotools,
           i.e. using POTFILES.in and LINGUAS files

               # LINGUAS
               en pl
               #end

               # POTFILES.in
               a.cpp
               b.cpp
               # end

               # SConscript
               env = Environment( tools = ["default", "gettext"] )
               env['POAUTOINIT'] = 1
               env['XGETTEXTPATH'] = ['../']
               env.Translate(LINGUAS_FILE = 1, XGETTEXTFROM = 'POTFILES.in')

           The last approach is perhaps the recommended one. It allows easily split
           internationalization/localization onto separate SCons scripts, where a script in
           source tree is responsible for translations (from sources to PO files) and script(s)
           under variant directories are responsible for compilation of PO to MO files to and for
           installation of MO files. The "gluing factor" synchronizing these two scripts is then
           the content of LINGUAS file. Note, that the updated POT and PO files are usually going
           to be committed back to the repository, so they must be updated within the source
           directory (and not in variant directories). Additionaly, the file listing of po/
           directory contains LINGUAS file, so the source tree looks familiar to translators, and
           they may work with the project in their usual way.

           Example 3. Let's prepare a development tree as below

                project/
                 + SConstruct
                 + build/
                 + src/
                     + po/
                         + SConscript
                         + SConscript.i18n
                         + POTFILES.in
                         + LINGUAS

           with build being variant directory. Write the top-level SConstruct script as follows

                 # SConstruct
                 env = Environment( tools = ["default", "gettext"] )
                 VariantDir('build', 'src', duplicate = 0)
                 env['POAUTOINIT'] = 1
                 SConscript('src/po/SConscript.i18n', exports = 'env')
                 SConscript('build/po/SConscript', exports = 'env')

           the src/po/SConscript.i18n as

                 # src/po/SConscript.i18n
                 Import('env')
                 env.Translate(LINGUAS_FILE=1, XGETTEXTFROM='POTFILES.in', XGETTEXTPATH=['../'])

           and the src/po/SConscript

                 # src/po/SConscript
                 Import('env')
                 env.MOFiles(LINGUAS_FILE = 1)

           Such setup produces POT and PO files under source tree in src/po/ and binary MO files
           under variant tree in build/po/. This way the POT and PO files are separated from
           other output files, which must not be committed back to source repositories (e.g.  MO
           files).

               Note
               In above example, the PO files are not updated, nor created automatically when you
               issue scons '.' command. The files must be updated (created) by hand via scons
               po-update and then MO files can be compiled by running scons '.'.

       TypeLibrary(), env.TypeLibrary()
           Builds a Windows type library (.tlb) file from an input IDL file (.idl). In addition,
           it will build the associated interface stub and proxy source files, naming them
           according to the base name of the .idl file. For example,

               env.TypeLibrary(source="foo.idl")

           Will create foo.tlb, foo.h, foo_i.c, foo_p.c and foo_data.c files.

       Uic(), env.Uic()
           Builds a header file, an implementation file and a moc file from an ui file. and
           returns the corresponding nodes in the that order. This builder is only available
           after using the tool qt3. Note: you can specify .ui files directly as source files to
           the Program, Library and SharedLibrary builders without using this builder. Using this
           builder lets you override the standard naming conventions (be careful: prefixes are
           always prepended to names of built files; if you don't want prefixes, you may set them
           to ``). See the $QT3DIR variable for more information. Example:

               env.Uic('foo.ui')  # -> ['foo.h', 'uic_foo.cc', 'moc_foo.cc']
               env.Uic(
                   target=Split('include/foo.h gen/uicfoo.cc gen/mocfoo.cc'),
                   source='foo.ui'
               )  # -> ['include/foo.h', 'gen/uicfoo.cc', 'gen/mocfoo.cc']

       Zip(), env.Zip()
           Builds a zip archive of the specified files and/or directories. Unlike most builder
           methods, the Zip builder method may be called multiple times for a given target; each
           additional call adds to the list of entries that will be built into the archive. Any
           source directories will be scanned for changes to any on-disk files, regardless of
           whether or not scons knows about them from other Builder or function calls.

               env.Zip('src.zip', 'src')

               # Create the stuff.zip file.
               env.Zip('stuff', ['subdir1', 'subdir2'])
               # Also add "another" to the stuff.tar file.
               env.Zip('stuff', 'another')

       All targets of builder methods automatically depend on their sources. An explicit
       dependency can be specified using the env.Depends method of a construction environment
       (see below).

       In addition, scons automatically scans source files for various programming languages, so
       the dependencies do not need to be specified explicitly. By default, SCons can C source
       files, C++ source files, Fortran source files with .F (POSIX systems only), .fpp, or .FPP
       file extensions, and assembly language files with .S (POSIX systems only), .spp, or .SPP
       files extensions for C preprocessor dependencies. SCons also has default support for
       scanning D source files, You can also write your own Scanners to add support for
       additional source file types. These can be added to the default Scanner object used by the
       Object, StaticObject and SharedObject Builders by adding them to the SourceFileScanner
       object. See the section called “Scanner Objects” for more information about defining your
       own Scanner objects and using the SourceFileScanner object.

   Methods and Functions To Do Things
       In addition to Builder methods, scons provides a number of other construction environment
       methods and global functions to manipulate the build configuration.

       Usually, a construction environment method and global function with the same name both
       exist for convenience. In the following list, the global function is documented in this
       style:

           Function(arguments, [optional arguments])

       and the construction environment method looks like:

           env.Function(arguments, [optional arguments])

       If the function can be called both ways, then both forms are listed.

       The global function and same-named construction environment method provide almost
       identical functionality, with a couple of exceptions. First, many of the construction
       environment methods affect only that construction environment, while the global function
       has a global effect. Second, where appropriate, calling the functionality through a
       construction environment will substitute construction variables into any supplied string
       arguments, while the global function doesn't have the context of a construction
       environment to pick variables from, so it cannot perform the substitution. For example:

           Default('$FOO')

           env = Environment(FOO='foo')
           env.Default('$FOO')

       In the above example, the call to the global Default function will add a target named $FOO
       to the list of default targets, while the call to the env.Default construction environment
       method will expand the value and add a target named foo to the list of default targets.
       For more on construction variable expansion, see the next section on construction
       variables.

       Global functions may be called from custom Python modules that you import into an
       SConscript file by adding the following import to the Python module:

           from SCons.Script import *

       Construction environment methods and global functions provided by scons include:

       Action(action, [output, [var, ...]] [key=value, ...]), env.Action(action, [output, [var,
       ...]] [key=value, ...])
           A factory function to create an Action object for the specified action. See the
           manpage section "Action Objects" for a complete explanation of the arguments and
           behavior.

           Note that the env.Action form of the invocation will expand construction variables in
           any argument strings, including the action argument, at the time it is called using
           the construction variables in the env construction environment through which
           env.Action was called. The Action global function form delays all variable expansion
           until the Action object is actually used.

       AddMethod(object, function, [name]), env.AddMethod(function, [name])
           Adds function to an object as a method.  function will be called with an instance
           object as the first argument as for other methods. If name is given, it is used as the
           name of the new method, else the name of function is used.

           When the global function AddMethod is called, the object to add the method to must be
           passed as the first argument; typically this will be Environment, in order to create a
           method which applies to all construction environments subsequently constructed. When
           called using the env.AddMethod form, the method is added to the specified construction
           environment only. Added methods propagate through env.Clone calls.

           More examples:

               # Function to add must accept an instance argument.
               # The Python convention is to call this 'self'.
               def my_method(self, arg):
                   print("my_method() got", arg)

               # Use the global function to add a method to the Environment class:
               AddMethod(Environment, my_method)
               env = Environment()
               env.my_method('arg')

               # Use the optional name argument to set the name of the method:
               env.AddMethod(my_method, 'other_method_name')
               env.other_method_name('another arg')

       AddOption(arguments)
           Adds a local (project-specific) command-line option.  arguments are the same as those
           supported by the add_option method in the standard Python library module optparse,
           with a few additional capabilities noted below. See the documentation for optparse for
           a thorough discussion of its option-processing capabities.

           In addition to the arguments and values supported by the optparse add_option method,
           AddOption allows setting the nargs keyword value to a string consisting of a question
           mark ('?') to indicate that the option argument for that option string is optional. If
           the option string is present on the command line but has no matching option argument,
           the value of the const keyword argument is produced as the value of the option. If the
           option string is omitted from the command line, the value of the default keyword
           argument is produced, as usual; if there is no default keyword argument in the
           AddOption call, None is produced.

           optparse recognizes abbreviations of long option names, as long as they can be
           unambiguously resolved. For example, if add_option is called to define a --devicename
           option, it will recognize --device, --dev and so forth as long as there is no other
           option which could also match to the same abbreviation. Options added via AddOption do
           not support the automatic recognition of abbreviations. Instead, to allow specific
           abbreviations, include them as synonyms in the AddOption call itself.

           Once a new command-line option has been added with AddOption, the option value may be
           accessed using GetOption or env.GetOption.  SetOption is not currently supported for
           options added with AddOption.

           Help text for an option is a combination of the string supplied in the help keyword
           argument to AddOption and information collected from the other keyword arguments. Such
           help is displayed if the -h command line option is used (but not with -H). Help for
           all local options is displayed under the separate heading Local Options. The options
           are unsorted - they will appear in the help text in the order in which the AddOption
           calls occur.

           Example:

               AddOption(
                   '--prefix',
                   dest='prefix',
                   nargs=1,
                   type='string',
                   action='store',
                   metavar='DIR',
                   help='installation prefix',
               )
               env = Environment(PREFIX=GetOption('prefix'))

           For that example, the following help text would be produced:

               Local Options:
                 --prefix=DIR                installation prefix

           Help text for local options may be unavailable if the Help function has been called,
           see the Help documentation for details.

               Note
               As an artifact of the internal implementation, the behavior of options added by
               AddOption which take option arguments is undefined if whitespace (rather than an =
               sign) is used as the separator on the command line. Users should avoid such usage;
               it is recommended to add a note to this effect to project documentation if the
               situation is likely to arise. In addition, if the nargs keyword is used to specify
               more than one following option argument (that is, with a value of 2 or greater),
               such arguments would necessarily be whitespace separated, triggering the issue.
               Developers should not use AddOption this way. Future versions of SCons will likely
               forbid such usage.

       AddPostAction(target, action), env.AddPostAction(target, action)
           Arranges for the specified action to be performed after the specified target has been
           built. The specified action(s) may be an Action object, or anything that can be
           converted into an Action object See the manpage section "Action Objects" for a
           complete explanation.

           When multiple targets are supplied, the action may be called multiple times, once
           after each action that generates one or more targets in the list.

       AddPreAction(target, action), env.AddPreAction(target, action)
           Arranges for the specified action to be performed before the specified target is
           built. The specified action(s) may be an Action object, or anything that can be
           converted into an Action object See the manpage section "Action Objects" for a
           complete explanation.

           When multiple targets are specified, the action(s) may be called multiple times, once
           before each action that generates one or more targets in the list.

           Note that if any of the targets are built in multiple steps, the action will be
           invoked just before the "final" action that specifically generates the specified
           target(s). For example, when building an executable program from a specified source .c
           file via an intermediate object file:

               foo = Program('foo.c')
               AddPreAction(foo, 'pre_action')

           The specified pre_action would be executed before scons calls the link command that
           actually generates the executable program binary foo, not before compiling the foo.c
           file into an object file.

       Alias(alias, [targets, [action]]), env.Alias(alias, [targets, [action]])
           Creates one or more phony targets that expand to one or more other targets. An
           optional action (command) or list of actions can be specified that will be executed
           whenever the any of the alias targets are out-of-date. Returns the Node object
           representing the alias, which exists outside of any file system. This Node object, or
           the alias name, may be used as a dependency of any other target, including another
           alias.  Alias can be called multiple times for the same alias to add additional
           targets to the alias, or additional actions to the list for this alias. Aliases are
           global even if set through the construction environment method.

           Examples:

               Alias('install')
               Alias('install', '/usr/bin')
               Alias(['install', 'install-lib'], '/usr/local/lib')

               env.Alias('install', ['/usr/local/bin', '/usr/local/lib'])
               env.Alias('install', ['/usr/local/man'])

               env.Alias('update', ['file1', 'file2'], "update_database $SOURCES")

       AllowSubstExceptions([exception, ...])
           Specifies the exceptions that will be allowed when expanding construction variables.
           By default, any construction variable expansions that generate a NameError or
           IndexError exception will expand to a '' (an empty string) and not cause scons to
           fail. All exceptions not in the specified list will generate an error message and
           terminate processing.

           If AllowSubstExceptions is called multiple times, each call completely overwrites the
           previous list of allowed exceptions.

           Example:

               # Requires that all construction variable names exist.
               # (You may wish to do this if you want to enforce strictly
               # that all construction variables must be defined before use.)
               AllowSubstExceptions()

               # Also allow a string containing a zero-division expansion
               # like '${1 / 0}' to evalute to ''.
               AllowSubstExceptions(IndexError, NameError, ZeroDivisionError)

       AlwaysBuild(target, ...), env.AlwaysBuild(target, ...)
           Marks each given target so that it is always assumed to be out of date, and will
           always be rebuilt if needed. Note, however, that AlwaysBuild does not add its
           target(s) to the default target list, so the targets will only be built if they are
           specified on the command line, or are a dependent of a target specified on the command
           line--but they will always be built if so specified. Multiple targets can be passed in
           to a single call to AlwaysBuild.

       env.Append(key=val, [...])
           Appends value(s) intelligently to construction variables in env. The construction
           variables and values to add to them are passed as key=val pairs (Python keyword
           arguments).  env.Append is designed to allow adding values without having to think
           about the data type of an existing construction variable. Regular Python syntax can
           also be used to manipulate the construction variable, but for that you may need to
           know the types involved, for example pure Python lets you directly "add" two lists of
           strings, but adding a string to a list or a list to a string requires different syntax
           - things Append takes care of. Some pre-defined construction variables do have type
           expectations based on how SCons will use them: for example $CPPDEFINES is often a
           string or a list of strings, but can also be a list of tuples or a dictionary; while
           $LIBEMITTER is expected to be a callable or list of callables, and $BUILDERS is
           expected to be a dictionary. Consult the documentation for the various construction
           variables for more details.

           The following descriptions apply to both the Append and Prepend methods, as well as
           their Unique variants, with the differences being the insertion point of the added
           values and whether duplication is allowed.

           val can be almost any type. If env does not have a construction variable named key,
           then key is simply stored with a value of val. Otherwise, val is combinined with the
           existing value, possibly converting into an appropriate type which can hold the
           expanded contents. There are a few special cases to be aware of. Normally, when two
           strings are combined, the result is a new string containing their concatenation (and
           you are responsible for supplying any needed separation); however, the contents of
           $CPPDEFINES will will be postprocessed by adding a prefix and/or suffix to each entry
           when the command line is produced, so SCons keeps them separate - appending a string
           will result in a separate string entry, not a combined string. For $CPPDEFINES. as
           well as $LIBS, and the various *PATH variables, SCons will amend the variable by
           supplying the compiler-specific syntax (e.g. prepending a -D or /D prefix for
           $CPPDEFINES), so you should omit this syntax when adding values to these variables.
           Examples (gcc syntax shown in the expansion of CPPDEFINES):

               env = Environment(CXXFLAGS="-std=c11", CPPDEFINES="RELEASE")
               print(f"CXXFLAGS = {env['CXXFLAGS']}, CPPDEFINES = {env['CPPDEFINES']}")
               # notice including a leading space in CXXFLAGS addition
               env.Append(CXXFLAGS=" -O", CPPDEFINES="EXTRA")
               print(f"CXXFLAGS = {env['CXXFLAGS']}, CPPDEFINES = {env['CPPDEFINES']}")
               print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))

               $ scons -Q
               CXXFLAGS = -std=c11, CPPDEFINES = RELEASE
               CXXFLAGS = -std=c11 -O, CPPDEFINES = deque(['RELEASE', 'EXTRA'])
               CPPDEFINES will expand to -DRELEASE -DEXTRA
               scons: `.' is up to date.

           Because $CPPDEFINES is intended for command-line specification of C/C++ preprocessor
           macros, additional syntax is accepted when adding to it. The preprocessor accepts
           arguments to predefine a macro name by itself (-DFOO for most compilers, /DFOO for
           Microsoft C++), which gives it an implicit value of 1, or can be given with a
           replacement value (-DBAR=TEXT).  SCons follows these rules when adding to $CPPDEFINES:

           •   A string is split on spaces, giving an easy way to enter multiple macros in one
               addition. Use an = to specify a valued macro.

           •   A tuple is treated as a valued macro. Use the value None if the macro should not
               have a value. It is an error to supply more than two elements in such a tuple.

           •   A list is processed in order, adding each item without further interpretation. In
               this case, space-separated strings are not split.

           •   A dictionary is processed in order, adding each key:value pair as a valued macro.
               Use the value None if the macro should not have a value.

           Examples:

               env = Environment(CPPDEFINES="FOO")
               print("CPPDEFINES =", env['CPPDEFINES'])
               env.Append(CPPDEFINES="BAR=1")
               print("CPPDEFINES =", env['CPPDEFINES'])
               env.Append(CPPDEFINES=[("OTHER", 2)])
               print("CPPDEFINES =", env['CPPDEFINES'])
               env.Append(CPPDEFINES={"EXTRA": "arg"})
               print("CPPDEFINES =", env['CPPDEFINES'])
               print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))

               $ scons -Q
               CPPDEFINES = FOO
               CPPDEFINES = deque(['FOO', 'BAR=1'])
               CPPDEFINES = deque(['FOO', 'BAR=1', ('OTHER', 2)])
               CPPDEFINES = deque(['FOO', 'BAR=1', ('OTHER', 2), ('EXTRA', 'arg')])
               CPPDEFINES will expand to -DFOO -DBAR=1 -DOTHER=2 -DEXTRA=arg
               scons: `.' is up to date.

           Examples of adding multiple macros:

               env = Environment()
               env.Append(CPPDEFINES=[("ONE", 1), "TWO", ("THREE", )])
               print("CPPDEFINES =", env['CPPDEFINES'])
               env.Append(CPPDEFINES={"FOUR": 4, "FIVE": None})
               print("CPPDEFINES =", env['CPPDEFINES'])
               print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))

               $ scons -Q
               CPPDEFINES = [('ONE', 1), 'TWO', ('THREE',)]
               CPPDEFINES = deque([('ONE', 1), 'TWO', ('THREE',), ('FOUR', 4), ('FIVE', None)])
               CPPDEFINES will expand to -DONE=1 -DTWO -DTHREE -DFOUR=4 -DFIVE
               scons: `.' is up to date.

           Changed in version 4.5: clarifined the use of tuples vs. other types, handling is now
           consistent across the four functions.

               env = Environment()
               env.Append(CPPDEFINES=("MACRO1", "MACRO2"))
               print("CPPDEFINES =", env['CPPDEFINES'])
               env.Append(CPPDEFINES=[("MACRO3", "MACRO4")])
               print("CPPDEFINES =", env['CPPDEFINES'])
               print("CPPDEFINES will expand to", env.subst('$_CPPDEFFLAGS'))

               $ scons -Q
               CPPDEFINES = ('MACRO1', 'MACRO2')
               CPPDEFINES = deque(['MACRO1', 'MACRO2', ('MACRO3', 'MACRO4')])
               CPPDEFINES will expand to -DMACRO1 -DMACRO2 -DMACRO3=MACRO4
               scons: `.' is up to date.

           See $CPPDEFINES for more details.

           Appending a string val to a dictonary-typed construction variable enters val as the
           key in the dictionary, and None as its value. Using a tuple type to supply a key,
           value only works for the special case of $CPPDEFINES described above.

           Although most combinations of types work without needing to know the details, some
           combinations do not make sense and Python raises an exception.

           When using env.Append to modify construction variables which are path specifications
           (conventionally, the names of such end in PATH), it is recommended to add the values
           as a list of strings, even if you are only adding a single string. The same goes for
           adding library names to $LIBS.

               env.Append(CPPPATH=["#/include"])

           See also env.AppendUnique, env.Prepend and env.PrependUnique.

       env.AppendENVPath(name, newpath, [envname, sep, delete_existing=False])
           Append path elements specified by newpath to the given search path string or list name
           in mapping envname in the construction environment. Supplying envname is optional: the
           default is the execution environment $ENV. Optional sep is used as the search path
           separator, the default is the platform's separator (os.pathsep). A path element will
           only appear once. Any duplicates in newpath are dropped, keeping the last appearing
           (to preserve path order). If delete_existing is False (the default) any addition
           duplicating an existing path element is ignored; if delete_existing is True the
           existing value will be dropped and the path element will be added at the end. To help
           maintain uniqueness all paths are normalized (using os.path.normpath and
           os.path.normcase).

           Example:

               print('before:', env['ENV']['INCLUDE'])
               include_path = '/foo/bar:/foo'
               env.AppendENVPath('INCLUDE', include_path)
               print('after:', env['ENV']['INCLUDE'])

           Yields:

               before: /foo:/biz
               after: /biz:/foo/bar:/foo

           See also env.PrependENVPath.

       env.AppendUnique(key=val, [...], [delete_existing=False])
           Append values to construction variables in the current construction environment,
           maintaining uniqueness. Works like env.Append, except that values that would become
           duplicates are not added. If delete_existing is set to a true value, then for any
           duplicate, the existing instance of val is first removed, then val is appended, having
           the effect of moving it to the end.

           Example:

               env.AppendUnique(CCFLAGS='-g', FOO=['foo.yyy'])

           See also env.Append, env.Prepend and env.PrependUnique.

       Builder(action, [arguments]), env.Builder(action, [arguments])
           Creates a Builder object for the specified action. See the manpage section "Builder
           Objects" for a complete explanation of the arguments and behavior.

           Note that the env.Builder() form of the invocation will expand construction variables
           in any arguments strings, including the action argument, at the time it is called
           using the construction variables in the env construction environment through which
           env.Builder was called. The Builder form delays all variable expansion until after the
           Builder object is actually called.

       CacheDir(cache_dir, custom_class=None), env.CacheDir(cache_dir, custom_class=None)
           Direct scons to maintain a derived-file cache in cache_dir. The derived files in the
           cache will be shared among all the builds specifying the same cache_dir. Specifying a
           cache_dir of None disables derived file caching.

           When specifying a custom_class which should be a class type which is a subclass of
           SCons.CacheDir.CacheDir, SCons will internally invoke this class to use for performing
           caching operations. This argument is optional and if left to default None, will use
           the default SCons.CacheDir.CacheDir class.

           Calling the environment method env.CacheDir limits the effect to targets built through
           the specified construction environment. Calling the global function CacheDir sets a
           global default that will be used by all targets built through construction
           environments that do not set up environment-specific caching by calling env.CacheDir.

           When derived-file caching is being used and scons finds a derived file that needs to
           be rebuilt, it will first look in the cache to see if a file with matching build
           signature exists (indicating the input file(s) and build action(s) were identical to
           those for the current target), and if so, will retrieve the file from the cache.
           scons will report Retrieved `file' from cache instead of the normal build message. If
           the derived file is not present in the cache, scons will build it and then place a
           copy of the built file in the cache, identified by its build signature, for future
           use.

           The Retrieved `file' from cache messages are useful for human consumption, but less so
           when comparing log files between scons runs which will show differences that are noisy
           and not actually significant. To disable, use the --cache-show option. With this
           option, scons will print the action that would have been used to build the file
           without considering cache retrieval.

           Derived-file caching may be disabled for any invocation of scons by giving the
           --cache-disable command line option. Cache updating may be disabled, leaving cache
           fetching enabled, by giving the --cache-readonly.

           If the --cache-force option is used, scons will place a copy of all derived files in
           the cache, even if they already existed and were not built by this invocation. This is
           useful to populate a cache the first time a cache_dir is used for a build, or to bring
           a cache up to date after a build with cache updating disabled (--cache-disable or
           --cache-readonly) has been done.

           The NoCache method can be used to disable caching of specific files. This can be
           useful if inputs and/or outputs of some tool are impossible to predict or
           prohibitively large.

           Note that (at this time) SCons provides no facilities for managing the derived-file
           cache. It is up to the developer to arrange for cache pruning, expiry, etc. if needed.

       Clean(targets, files_or_dirs), env.Clean(targets, files_or_dirs)
           This specifies a list of files or directories which should be removed whenever the
           targets are specified with the -c command line option. The specified targets may be a
           list or an individual target. Multiple calls to Clean are legal, and create new
           targets or add files and directories to the clean list for the specified targets.

           Multiple files or directories should be specified either as separate arguments to the
           Clean method, or as a list.  Clean will also accept the return value of any of the
           construction environment Builder methods. Examples:

           The related NoClean function overrides calling Clean for the same target, and any
           targets passed to both functions will not be removed by the -c option.

           Examples:

               Clean('foo', ['bar', 'baz'])
               Clean('dist', env.Program('hello', 'hello.c'))
               Clean(['foo', 'bar'], 'something_else_to_clean')

           In this example, installing the project creates a subdirectory for the documentation.
           This statement causes the subdirectory to be removed if the project is deinstalled.

               Clean(docdir, os.path.join(docdir, projectname))

       env.Clone([key=val, ...])
           Returns a separate copy of a construction environment. If there are any keyword
           arguments specified, they are added to the returned copy, overwriting any existing
           values for the keywords.

           Example:

               env2 = env.Clone()
               env3 = env.Clone(CCFLAGS='-g')

           Additionally, a list of tools and a toolpath may be specified, as in the Environment
           constructor:

               def MyTool(env):
                   env['FOO'] = 'bar'

               env4 = env.Clone(tools=['msvc', MyTool])

           The parse_flags keyword argument is also recognized to allow merging command-line
           style arguments into the appropriate construction variables (see env.MergeFlags).

               # create an environment for compiling programs that use wxWidgets
               wx_env = env.Clone(parse_flags='!wx-config --cflags --cxxflags')

       Command(target, source, action, [key=val, ...]), env.Command(target, source, action,
       [key=val, ...])
           Executes a specific action (or list of actions) to build a target file or files from a
           source file or files. This is more convenient than defining a separate Builder object
           for a single special-case build.

           The Command function accepts source_scanner, target_scanner, source_factory, and
           target_factory keyword arguments. These arguments can be used to specify a Scanner
           object that will be used to apply a custom scanner for a source or target. For
           example, the global DirScanner object can be used if any of the sources will be
           directories that must be scanned on-disk for changes to files that aren't already
           specified in other Builder of function calls. The *_factory arguments take a factory
           function that Command will use to turn any sources or targets specified as strings
           into SCons Nodes. See the manpage section "Builder Objects" for more information about
           how these arguments work in a Builder.

           Any other keyword arguments specified override any same-named existing construction
           variables.

           An action can be an external command, specified as a string, or a callable Python
           object; see the manpage section "Action Objects" for more complete information. Also
           note that a string specifying an external command may be preceded by an at-sign (@) to
           suppress printing the command in question, or by a hyphen (-) to ignore the exit
           status of the external command.

           Examples:

               env.Command(
                   target='foo.out',
                   source='foo.in',
                   action="$FOO_BUILD < $SOURCES > $TARGET"
               )

               env.Command(
                   target='bar.out',
                   source='bar.in',
                   action=["rm -f $TARGET", "$BAR_BUILD < $SOURCES > $TARGET"],
                   ENV={'PATH': '/usr/local/bin/'},
               )

               import os
               def rename(env, target, source):
                   os.rename('.tmp', str(target[0]))

               env.Command(
                   target='baz.out',
                   source='baz.in',
                   action=["$BAZ_BUILD < $SOURCES > .tmp", rename],
               )

           Note that the Command function will usually assume, by default, that the specified
           targets and/or sources are Files, if no other part of the configuration identifies
           what type of entries they are. If necessary, you can explicitly specify that targets
           or source nodes should be treated as directories by using the Dir or env.Dir
           functions.

           Examples:

               env.Command('ddd.list', Dir('ddd'), 'ls -l $SOURCE > $TARGET')

               env['DISTDIR'] = 'destination/directory'
               env.Command(env.Dir('$DISTDIR')), None, make_distdir)

           Also note that SCons will usually automatically create any directory necessary to hold
           a target file, so you normally don't need to create directories by hand.

       Configure(env, [custom_tests, conf_dir, log_file, config_h]), env.Configure([custom_tests,
       conf_dir, log_file, config_h])
           Creates a Configure object for integrated functionality similar to GNU autoconf. See
           the manpage section "Configure Contexts" for a complete explanation of the arguments
           and behavior.

       Decider(function), env.Decider(function)
           Specifies that all up-to-date decisions for targets built through this construction
           environment will be handled by the specified function.  function can be the name of a
           function or one of the following strings that specify the predefined decision function
           that will be applied:

           "timestamp-newer"
               Specifies that a target shall be considered out of date and rebuilt if the
               dependency's timestamp is newer than the target file's timestamp. This is the
               behavior of the classic Make utility, and make can be used a synonym for
               timestamp-newer.

           "timestamp-match"
               Specifies that a target shall be considered out of date and rebuilt if the
               dependency's timestamp is different than the timestamp recorded the last time the
               target was built. This provides behavior very similar to the classic Make utility
               (in particular, files are not opened up so that their contents can be checksummed)
               except that the target will also be rebuilt if a dependency file has been restored
               to a version with an earlier timestamp, such as can happen when restoring files
               from backup archives.

           "content"
               Specifies that a target shall be considered out of date and rebuilt if the
               dependency's content has changed since the last time the target was built, as
               determined be performing an checksum on the dependency's contents and comparing it
               to the checksum recorded the last time the target was built.  MD5 can be used as a
               synonym for content, but it is deprecated.

           "content-timestamp"
               Specifies that a target shall be considered out of date and rebuilt if the
               dependency's content has changed since the last time the target was built, except
               that dependencies with a timestamp that matches the last time the target was
               rebuilt will be assumed to be up-to-date and not rebuilt. This provides behavior
               very similar to the content behavior of always checksumming file contents, with an
               optimization of not checking the contents of files whose timestamps haven't
               changed. The drawback is that SCons will not detect if a file's content has
               changed but its timestamp is the same, as might happen in an automated script that
               runs a build, updates a file, and runs the build again, all within a single
               second.  MD5-timestamp can be used as a synonym for content-timestamp, but it is
               deprecated.

           Examples:

               # Use exact timestamp matches by default.
               Decider('timestamp-match')

               # Use hash content signatures for any targets built
               # with the attached construction environment.
               env.Decider('content')

           In addition to the above already-available functions, the function argument may be a
           Python function you supply. Such a function must accept the following four arguments:

           dependency
               The Node (file) which should cause the target to be rebuilt if it has "changed"
               since the last tme target was built.

           target
               The Node (file) being built. In the normal case, this is what should get rebuilt
               if the dependency has "changed."

           prev_ni
               Stored information about the state of the dependency the last time the target was
               built. This can be consulted to match various file characteristics such as the
               timestamp, size, or content signature.

           repo_node
               If set, use this Node instead of the one specified by dependency to determine if
               the dependency has changed. This argument is optional so should be written as a
               default argument (typically it would be written as repo_node=None). A caller will
               normally only set this if the target only exists in a Repository.

           The function should return a value which evaluates True if the dependency has
           "changed" since the last time the target was built (indicating that the target should
           be rebuilt), and a value which evaluates False otherwise (indicating that the target
           should not be rebuilt). Note that the decision can be made using whatever criteria are
           appopriate. Ignoring some or all of the function arguments is perfectly normal.

           Example:

               def my_decider(dependency, target, prev_ni, repo_node=None):
                   return not os.path.exists(str(target))

               env.Decider(my_decider)

       Default(target[, ...]), env.Default(target[, ...])
           Specify default targets to the SCons target selection mechanism. Any call to Default
           will cause SCons to use the defined default target list instead of its built-in
           algorithm for determining default targets (see the manpage section "Target
           Selection").

           target may be one or more strings, a list of strings, a NodeList as returned by a
           Builder, or None. A string target may be the name of a file or directory, or a target
           previously defined by a call to Alias (defining the alias later will still create the
           alias, but it will not be recognized as a default). Calls to Default are additive. A
           target of None will clear any existing default target list; subsequent calls to
           Default will add to the (now empty) default target list like normal.

           Both forms of this call affect the same global list of default targets; the
           construction environment method applies construction variable expansion to the
           targets.

           The current list of targets added using Default is available in the DEFAULT_TARGETS
           list (see below).

           Examples:

               Default('foo', 'bar', 'baz')
               env.Default(['a', 'b', 'c'])
               hello = env.Program('hello', 'hello.c')
               env.Default(hello)

       DefaultEnvironment([**kwargs])
           Instantiates and returns the default construction environment object. The default
           environment is used internally by SCons in order to execute many of the global
           functions in this list (that is, those not called as methods of a specific
           construction environment). It is not mandatory to call DefaultEnvironment: the default
           environment will be instantiated automatically when the build phase begins if the
           function has not been called, however calling it explicitly gives the opportunity to
           affect and examine the contents of the default environment.

           The default environment is a singleton, so the keyword arguments affect it only on the
           first call, on subsequent calls the already-constructed object is returned and any
           keyword arguments are silently ignored. The default environment can be modified after
           instantiation in the same way as any construction environment. Modifying the default
           environment has no effect on the construction environment constructed by an
           Environment or Clone call.

       Depends(target, dependency), env.Depends(target, dependency)
           Specifies an explicit dependency; the target will be rebuilt whenever the dependency
           has changed. Both the specified target and dependency can be a string (usually the
           path name of a file or directory) or Node objects, or a list of strings or Node
           objects (such as returned by a Builder call). This should only be necessary for cases
           where the dependency is not caught by a Scanner for the file.

           Example:

               env.Depends('foo', 'other-input-file-for-foo')

               mylib = env.Library('mylib.c')
               installed_lib = env.Install('lib', mylib)
               bar = env.Program('bar.c')

               # Arrange for the library to be copied into the installation
               # directory before trying to build the "bar" program.
               # (Note that this is for example only.  A "real" library
               # dependency would normally be configured through the $LIBS
               # and $LIBPATH variables, not using an env.Depends() call.)

               env.Depends(bar, installed_lib)

       env.Detect(progs)
           Find an executable from one or more choices: progs may be a string or a list of
           strings. Returns the first value from progs that was found, or None. Executable is
           searched by checking the paths in the execution environment (env['ENV']['PATH']). On
           Windows systems, additionally applies the filename suffixes found in the execution
           environment (env['ENV']['PATHEXT']) but will not include any such extension in the
           return value.  env.Detect is a wrapper around env.WhereIs.

       env.Dictionary([vars])
           Returns a dictionary object containing the construction variables in the construction
           environment. If there are any arguments specified, the values of the specified
           construction variables are returned as a string (if one argument) or as a list of
           strings.

           Example:

               cvars = env.Dictionary()
               cc_values = env.Dictionary('CC', 'CCFLAGS', 'CCCOM')

       Dir(name, [directory]), env.Dir(name, [directory])
           Returns Directory Node(s). A Directory Node is an object that represents a directory.
           name can be a relative or absolute path or a list of such paths.  directory is an
           optional directory that will be used as the parent directory. If no directory is
           specified, the current script's directory is used as the parent.

           If name is a single pathname, the corresponding node is returned. If name is a list,
           SCons returns a list of nodes. Construction variables are expanded in name.

           Directory Nodes can be used anywhere you would supply a string as a directory name to
           a Builder method or function. Directory Nodes have attributes and methods that are
           useful in many situations; see manpage section "File and Directory Nodes" for more
           information.

       env.Dump([key], [format])
           Serializes construction variables to a string. The method supports the following
           formats specified by format:

           pretty
               Returns a pretty printed representation of the environment (if format is not
               specified, this is the default).

           json
               Returns a JSON-formatted string representation of the environment.

           If key is None (the default) the entire dictionary of construction variables is
           serialized. If supplied, it is taken as the name of a construction variable whose
           value is serialized.

           This SConstruct:

               env=Environment()
               print(env.Dump('CCCOM'))

           will print:

               '$CC -c -o $TARGET $CCFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS $SOURCES'

           While this SConstruct:

               env = Environment()
               print(env.Dump())

           will print:

               { 'AR': 'ar',
                 'ARCOM': '$AR $ARFLAGS $TARGET $SOURCES\n$RANLIB $RANLIBFLAGS $TARGET',
                 'ARFLAGS': ['r'],
                 'AS': 'as',
                 'ASCOM': '$AS $ASFLAGS -o $TARGET $SOURCES',
                 'ASFLAGS': [],
                 ...

       EnsurePythonVersion(major, minor)
           Ensure that the Python version is at least major.minor. This function will print out
           an error message and exit SCons with a non-zero exit code if the actual Python version
           is not late enough.

           Example:

               EnsurePythonVersion(2,2)

       EnsureSConsVersion(major, minor, [revision])
           Ensure that the SCons version is at least major.minor, or major.minor.revision. if
           revision is specified. This function will print out an error message and exit SCons
           with a non-zero exit code if the actual SCons version is not late enough.

           Examples:

               EnsureSConsVersion(0,14)

               EnsureSConsVersion(0,96,90)

       Environment([key=value, ...]), env.Environment([key=value, ...])
           Return a new construction environment initialized with the specified key=value pairs.
           The keyword arguments parse_flags, platform, toolpath, tools and variables are also
           specially recognized. See the manpage section "Construction Environments" for more
           details.

       Execute(action, [actionargs ...]), env.Execute(action, [actionargs ...])
           Executes an Action.  action may be an Action object or it may be a command-line
           string, list of commands, or executable Python function, each of which will first be
           converted into an Action object and then executed. Any additional arguments to Execute
           are passed on to the Action factory function which actually creates the Action object
           (see the manpage section Action Objects for a description). Example:

               Execute(Copy('file.out', 'file.in'))

           Execute performs its action immediately, as part of the SConscript-reading phase.
           There are no sources or targets declared in an Execute call, so any objects it
           manipulates will not be tracked as part of the SCons dependency graph. In the example
           above, neither file.out nor file.in will be tracked objects.

           Execute returns the exit value of the command or return value of the Python function.
           scons prints an error message if the executed action fails (exits with or returns a
           non-zero value), however it does not, automatically terminate the build for such a
           failure. If you want the build to stop in response to a failed Execute call, you must
           explicitly check for a non-zero return value:

               if Execute("mkdir sub/dir/ectory"):
                   # The mkdir failed, don't try to build.
                   Exit(1)

       Exit([value])
           This tells scons to exit immediately with the specified value. A default exit value of
           0 (zero) is used if no value is specified.

       Export([vars...], [key=value...]), env.Export([vars...], [key=value...])
           Exports variables from the current SConscript file to a global collection where they
           can be imported by other SConscript files.  vars may be one or more strings
           representing variable names to be exported. If a string contains whitespace, it is
           split into separate strings, as if multiple string arguments had been given. A vars
           argument may also be a dictionary, which can be used to map variables to different
           names when exported. Keyword arguments can be used to provide names and their values.

           Export calls are cumulative. Specifying a previously exported variable will overwrite
           the earlier value. Both local variables and global variables can be exported.

           Examples:

               env = Environment()
               # Make env available for all SConscript files to Import().
               Export("env")

               package = 'my_name'
               # Make env and package available for all SConscript files:.
               Export("env", "package")

               # Make env and package available for all SConscript files:
               Export(["env", "package"])

               # Make env available using the name debug:
               Export(debug=env)

               # Make env available using the name debug:
               Export({"debug": env})

           Note that the SConscript function supports an exports argument that allows exporting a
           variable or set of variables to a specific SConscript file or files. See the
           description below.

       File(name, [directory]), env.File(name, [directory])
           Returns File Node(s). A File Node is an object that represents a file.  name can be a
           relative or absolute path or a list of such paths.  directory is an optional directory
           that will be used as the parent directory. If no directory is specified, the current
           script's directory is used as the parent.

           If name is a single pathname, the corresponding node is returned. If name is a list,
           SCons returns a list of nodes. Construction variables are expanded in name.

           File Nodes can be used anywhere you would supply a string as a file name to a Builder
           method or function. File Nodes have attributes and methods that are useful in many
           situations; see manpage section "File and Directory Nodes" for more information.

       FindFile(file, dirs), env.FindFile(file, dirs)
           Search for file in the path specified by dirs.  dirs may be a list of directory names
           or a single directory name. In addition to searching for files that exist in the
           filesystem, this function also searches for derived files that have not yet been
           built.

           Example:

               foo = env.FindFile('foo', ['dir1', 'dir2'])

       FindInstalledFiles(), env.FindInstalledFiles()
           Returns the list of targets set up by the Install or InstallAs builders.

           This function serves as a convenient method to select the contents of a binary
           package.

           Example:

               Install('/bin', ['executable_a', 'executable_b'])

               # will return the file node list
               # ['/bin/executable_a', '/bin/executable_b']
               FindInstalledFiles()

               Install('/lib', ['some_library'])

               # will return the file node list
               # ['/bin/executable_a', '/bin/executable_b', '/lib/some_library']
               FindInstalledFiles()

       FindPathDirs(variable)
           Returns a function (actually a callable Python object) intended to be used as the
           path_function of a Scanner object. The returned object will look up the specified
           variable in a construction environment and treat the construction variable's value as
           a list of directory paths that should be searched (like $CPPPATH, $LIBPATH, etc.).

           Note that use of FindPathDirs is generally preferable to writing your own
           path_function for the following reasons: 1) The returned list will contain all
           appropriate directories found in source trees (when VariantDir is used) or in code
           repositories (when Repository or the -Y option are used). 2) scons will identify
           expansions of variable that evaluate to the same list of directories as, in fact, the
           same list, and avoid re-scanning the directories for files, when possible.

           Example:

               def my_scan(node, env, path, arg):
                   # Code to scan file contents goes here...
                   return include_files

               scanner = Scanner(name = 'myscanner',
                                 function = my_scan,
                                 path_function = FindPathDirs('MYPATH'))

       FindSourceFiles(node='"."'), env.FindSourceFiles(node='"."')
           Returns the list of nodes which serve as the source of the built files. It does so by
           inspecting the dependency tree starting at the optional argument node which defaults
           to the '"."'-node. It will then return all leaves of node. These are all children
           which have no further children.

           This function is a convenient method to select the contents of a Source Package.

           Example:

               Program('src/main_a.c')
               Program('src/main_b.c')
               Program('main_c.c')

               # returns ['main_c.c', 'src/main_a.c', 'SConstruct', 'src/main_b.c']
               FindSourceFiles()

               # returns ['src/main_b.c', 'src/main_a.c' ]
               FindSourceFiles('src')

           As you can see build support files (SConstruct in the above example) will also be
           returned by this function.

       Flatten(sequence), env.Flatten(sequence)
           Takes a sequence (that is, a Python list or tuple) that may contain nested sequences
           and returns a flattened list containing all of the individual elements in any
           sequence. This can be helpful for collecting the lists returned by calls to Builders;
           other Builders will automatically flatten lists specified as input, but direct Python
           manipulation of these lists does not.

           Examples:

               foo = Object('foo.c')
               bar = Object('bar.c')

               # Because `foo' and `bar' are lists returned by the Object() Builder,
               # `objects' will be a list containing nested lists:
               objects = ['f1.o', foo, 'f2.o', bar, 'f3.o']

               # Passing such a list to another Builder is all right because
               # the Builder will flatten the list automatically:
               Program(source = objects)

               # If you need to manipulate the list directly using Python, you need to
               # call Flatten() yourself, or otherwise handle nested lists:
               for object in Flatten(objects):
                   print(str(object))

       GetBuildFailures()
           Returns a list of exceptions for the actions that failed while attempting to build
           targets. Each element in the returned list is a BuildError object with the following
           attributes that record various aspects of the build failure:

           .node The node that was being built when the build failure occurred.

           .status The numeric exit status returned by the command or Python function that failed
           when trying to build the specified Node.

           .errstr The SCons error string describing the build failure. (This is often a generic
           message like "Error 2" to indicate that an executed command exited with a status of
           2.)

           .filename The name of the file or directory that actually caused the failure. This may
           be different from the .node attribute. For example, if an attempt to build a target
           named sub/dir/target fails because the sub/dir directory could not be created, then
           the .node attribute will be sub/dir/target but the .filename attribute will be
           sub/dir.

           .executor The SCons Executor object for the target Node being built. This can be used
           to retrieve the construction environment used for the failed action.

           .action The actual SCons Action object that failed. This will be one specific action
           out of the possible list of actions that would have been executed to build the target.

           .command The actual expanded command that was executed and failed, after expansion of
           $TARGET, $SOURCE, and other construction variables.

           Note that the GetBuildFailures function will always return an empty list until any
           build failure has occurred, which means that GetBuildFailures will always return an
           empty list while the SConscript files are being read. Its primary intended use is for
           functions that will be executed before SCons exits by passing them to the standard
           Python atexit.register() function. Example:

               import atexit

               def print_build_failures():
                   from SCons.Script import GetBuildFailures
                   for bf in GetBuildFailures():
                       print("%s failed: %s" % (bf.node, bf.errstr))

               atexit.register(print_build_failures)

       GetBuildPath(file, [...]), env.GetBuildPath(file, [...])
           Returns the scons path name (or names) for the specified file (or files). The
           specified file or files may be scons Nodes or strings representing path names.

       GetLaunchDir()
           Returns the absolute path name of the directory from which scons was initially
           invoked. This can be useful when using the -u, -U or -D options, which internally
           change to the directory in which the SConstruct file is found.

       GetOption(name), env.GetOption(name)
           Query the value of settable options which may have been set on the command line, or by
           using the SetOption function. The value of the option is returned in a type matching
           how the option was declared - see the documentation for the corresponding command line
           option for information about each specific option.

           name can be an entry from the following table, which shows the corresponding command
           line arguments that could affect the value.  name can be also be the destination
           variable name from a project-specific option added using the AddOption function, as
           long as that addition has been processed prior to the GetOption call in the SConscript
           files.

           ┌────────────────────────┬───────────────────────────┬─────────────────────────┐
           │Query name              │ Command-line options      │ Notes                   │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │cache_debug             │ --cache-debug             │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │cache_disable           │ --cache-disable,          │                         │
           │                        │       --no-cache          │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │cache_force             │ --cache-force,            │                         │
           │                        │       --cache-populate    │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │cache_readonly          │ --cache-readonly          │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │cache_show              │ --cache-show              │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │clean                   │ -c,                       │                         │
           │                        │       --clean,            │                         │
           │                        │       --remove            │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │climb_up                │ -D                        │                         │
           │                        │       -U                  │                         │
           │                        │       -u                  │                         │
           │                        │       --up                │                         │
           │                        │       --search_up         │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │config                  │ --config                  │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │debug                   │ --debug                   │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │directory               │ -C, --directory           │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │diskcheck               │ --diskcheck               │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │duplicate               │ --duplicate               │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │enable_virtualenv       │ --enable-virtualenv       │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │experimental            │ --experimental            │ since 4.2               │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │file                    │ -f,                       │                         │
           │                        │       --file,             │                         │
           │                        │       --makefile,         │                         │
           │                        │       --sconstruct        │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │hash_format             │ --hash-format             │ since 4.2               │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │help                    │ -h, --help                │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │ignore_errors           │ -i, --ignore-errors       │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │ignore_virtualenv       │ --ignore-virtualenv       │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │implicit_cache          │ --implicit-cache          │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │implicit_deps_changed   │ --implicit-deps-changed   │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │implicit_deps_unchanged │ --implicit-deps-unchanged │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │include_dir             │ -I, --include-dir         │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │install_sandbox         │ --install-sandbox         │ Available only if the   │
           │                        │                           │ install tool has been   │
           │                        │                           │ called                  │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │keep_going              │ -k, --keep-going          │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │max_drift               │ --max-drift               │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │md5_chunksize           │ --hash-chunksize,         │ --hash-chunksize since  │
           │                        │       --md5-chunksize     │ 4.2                     │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │no_exec                 │ -n,                       │                         │
           │                        │       --no-exec,          │                         │
           │                        │       --just-print,       │                         │
           │                        │       --dry-run,          │                         │
           │                        │       --recon             │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │no_progress             │ -Q                        │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │num_jobs                │ -j, --jobs                │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │package_type            │ --package-type            │ Available only if the   │
           │                        │                           │ packaging tool has been │
           │                        │                           │ called                  │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │profile_file            │ --profile                 │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │question                │ -q, --question            │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │random                  │ --random                  │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │repository              │ -Y,                       │                         │
           │                        │       --repository,       │                         │
           │                        │       --srcdir            │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │silent                  │ -s,                       │                         │
           │                        │       --silent,           │                         │
           │                        │       --quiet             │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │site_dir                │ --site-dir, --no-site-dir │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │stack_size              │ --stack-size              │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │taskmastertrace_file    │ --taskmastertrace         │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │tree_printers           │ --tree                    │                         │
           ├────────────────────────┼───────────────────────────┼─────────────────────────┤
           │warn                    │ --warn, --warning         │                         │
           └────────────────────────┴───────────────────────────┴─────────────────────────┘

       Glob(pattern, [ondisk=True, source=False, strings=False, exclude=None]), env.Glob(pattern,
       [ondisk=True, source=False, strings=False, exclude=None])
           Returns a possibly empty list of Nodes (or strings) that match pathname specification
           pattern.  pattern can be absolute, top-relative, or (most commonly) relative to the
           directory of the current SConscript file.  Glob matches both files stored on disk and
           Nodes which SCons already knows about, even if any corresponding file is not currently
           stored on disk. The evironment method form (env.Glob) performs string substition on
           pattern and returns whatever matches the resulting expanded pattern. The results are
           sorted, unlike for the similar Python glob.glob function, to ensure build order will
           be stable.

           pattern can contain POSIX-style shell metacharacters for matching:

           ┌────────┬──────────────────────────────────┐
           │Pattern │ Meaning                          │
           ├────────┼──────────────────────────────────┤
           │*       │ matches everything               │
           ├────────┼──────────────────────────────────┤
           │?       │ matches any single character     │
           ├────────┼──────────────────────────────────┤
           │[seq]   │ matches any character in seq     │
           │        │       (can be a list or a        │
           │        │ range).                          │
           ├────────┼──────────────────────────────────┤
           │[!seq]  │ matches any character not in seq │
           └────────┴──────────────────────────────────┘
           For a literal match, wrap the metacharacter in brackets to escape the normal behavior.
           For example, '[?]' matches the character '?'.

           Filenames starting with a dot are specially handled - they can only be matched by
           patterns that start with a dot (or have a dot immediately following a pathname
           separator character, or slash), they are not not matched by the metacharacters.
           Metacharacter matches also do not span directory separators.

           Glob understands repositories (see the Repository function) and source directories
           (see the VariantDir function) and returns a Node (or string, if so configured) match
           in the local (SConscript) directory if a matching Node is found anywhere in a
           corresponding repository or source directory.

           If the optional ondisk argument evaluates false, the search for matches on disk is
           disabled, and only matches from already-configured File or Dir Nodes are returned. The
           default is to return Nodes for matches on disk as well.

           If the optional source argument evaluates true, and the local directory is a variant
           directory, then Glob returnes Nodes from the corresponding source directory, rather
           than the local directory.

           If the optional strings argument evaluates true, Glob returns matches as strings,
           rather than Nodes. The returned strings will be relative to the local (SConscript)
           directory. (Note that while this may make it easier to perform arbitrary manipulation
           of file names, it loses the context SCons would have in the Node, so if the returned
           strings are passed to a different SConscript file, any Node translation there will be
           relative to that SConscript directory, not to the original SConscript directory.)

           The optional exclude argument may be set to a pattern or a list of patterns descibing
           files or directories to filter out of the match list. Elements matching a least one
           specified pattern will be excluded. These patterns use the same syntax as for pattern.

           Examples:

               Program("foo", Glob("*.c"))
               Zip("/tmp/everything", Glob(".??*") + Glob("*"))
               sources = Glob("*.cpp", exclude=["os_*_specific_*.cpp"]) \
                   + Glob("os_%s_specific_*.cpp" % currentOS)

       Help(text, append=False), env.Help(text, append=False)
           Specifies a local help message to be printed if the -h argument is given to scons.
           Subsequent calls to Help append text to the previously defined local help text.

           For the first call to Help only, if append is False (the default) any local help
           message generated through AddOption calls is replaced. If append is True, text is
           appended to the existing help text.

       Ignore(target, dependency), env.Ignore(target, dependency)
           Ignores dependency when deciding if target needs to be rebuilt.  target and dependency
           can each be a single filename or Node or a list of filenames or Nodes.

           Ignore can also be used to remove a target from the default build by specifying the
           directory the target will be built in as target and the file you want to skip
           selecting for building as dependency. Note that this only removes the target from the
           default target selection algorithm: if it is a dependency of another object being
           built SCons still builds it normally. See the third and forth examples below.

           Examples:

               env.Ignore('foo', 'foo.c')
               env.Ignore('bar', ['bar1.h', 'bar2.h'])
               env.Ignore('.', 'foobar.obj')
               env.Ignore('bar', 'bar/foobar.obj')

       Import(vars...), env.Import(vars...)
           Imports variables into the current SConscript file.  vars must be strings representing
           names of variables which have been previously exported either by the Export function
           or by the exports argument to SConscript. Variables exported by SConscript take
           precedence. Multiple variable names can be passed to Import as separate arguments or
           as words in a space-separated string. The wildcard "*" can be used to import all
           available variables.

           Examples:

               Import("env")
               Import("env", "variable")
               Import(["env", "variable"])
               Import("*")

       Literal(string), env.Literal(string)
           The specified string will be preserved as-is and not have construction variables
           expanded.

       Local(targets), env.Local(targets)
           The specified targets will have copies made in the local tree, even if an already
           up-to-date copy exists in a repository. Returns a list of the target Node or Nodes.

       env.MergeFlags(arg, [unique])
           Merges values from arg into construction variables in the current construction
           environment. If arg is not a dictionary, it is converted to one by calling
           env.ParseFlags on the argument before the values are merged. Note that arg must be a
           single value, so multiple strings must be passed in as a list, not as separate
           arguments to env.MergeFlags.

           If unique is true (the default), duplicate values are not stored. When eliminating
           duplicate values, any construction variables that end with the string PATH keep the
           left-most unique value. All other construction variables keep the right-most unique
           value. If unique is false, values are added even if they are duplicates.

           Examples:

               # Add an optimization flag to $CCFLAGS.
               env.MergeFlags('-O3')

               # Combine the flags returned from running pkg-config with an optimization
               # flag and merge the result into the construction variables.
               env.MergeFlags(['!pkg-config gtk+-2.0 --cflags', '-O3'])

               # Combine an optimization flag with the flags returned from running pkg-config
               # twice and merge the result into the construction variables.
               env.MergeFlags(
                   [
                       '-O3',
                       '!pkg-config gtk+-2.0 --cflags --libs',
                       '!pkg-config libpng12 --cflags --libs',
                   ]
               )

       NoCache(target, ...), env.NoCache(target, ...)
           Specifies a list of files which should not be cached whenever the CacheDir method has
           been activated. The specified targets may be a list or an individual target.

           Multiple files should be specified either as separate arguments to the NoCache method,
           or as a list.  NoCache will also accept the return value of any of the construction
           environment Builder methods.

           Calling NoCache on directories and other non-File Node types has no effect because
           only File Nodes are cached.

           Examples:

               NoCache('foo.elf')
               NoCache(env.Program('hello', 'hello.c'))

       NoClean(target, ...), env.NoClean(target, ...)
           Specifies a list of files or directories which should not be removed whenever the
           targets (or their dependencies) are specified with the -c command line option. The
           specified targets may be a list or an individual target. Multiple calls to NoClean are
           legal, and prevent each specified target from being removed by calls to the -c option.

           Multiple files or directories should be specified either as separate arguments to the
           NoClean method, or as a list.  NoClean will also accept the return value of any of the
           construction environment Builder methods.

           Calling NoClean for a target overrides calling Clean for the same target, and any
           targets passed to both functions will not be removed by the -c option.

           Examples:

               NoClean('foo.elf')
               NoClean(env.Program('hello', 'hello.c'))

       env.ParseConfig(command, [function, unique])
           Updates the current construction environment with the values extracted from the output
           of running external command, by passing it to a helper function.  command may be a
           string or a list of strings representing the command and its arguments. If function is
           omitted or None, env.MergeFlags is used. By default, duplicate values are not added to
           any construction variables; you can specify unique=False to allow duplicate values to
           be added.

           command is executed using the SCons execution environment (that is, the construction
           variable $ENV in the current construction environment). If command needs additional
           information to operate properly, that needs to be set in the execution environment.
           For example, pkg-config may need a custom value set in the PKG_CONFIG_PATH environment
           variable.

           env.MergeFlags needs to understand the output produced by command in order to
           distribute it to appropriate construction variables.  env.MergeFlags uses a separate
           function to do that processing - see env.ParseFlags for the details, including a a
           table of options and corresponding construction variables. To provide alternative
           processing of the output of command, you can suppply a custom function, which must
           accept three arguments: the construction environment to modify, a string argument
           containing the output from running command, and the optional unique flag.

       ParseDepends(filename, [must_exist, only_one]), env.ParseDepends(filename, [must_exist,
       only_one])
           Parses the contents of filename as a list of dependencies in the style of Make or
           mkdep, and explicitly establishes all of the listed dependencies.

           By default, it is not an error if filename does not exist. The optional must_exist
           argument may be set to True to have SCons raise an exception if the file does not
           exist, or is otherwise inaccessible.

           The optional only_one argument may be set to True to have SCons raise an exception if
           the file contains dependency information for more than one target. This can provide a
           small sanity check for files intended to be generated by, for example, the gcc -M
           flag, which should typically only write dependency information for one output file
           into a corresponding .d file.

           filename and all of the files listed therein will be interpreted relative to the
           directory of the SConscript file which calls the ParseDepends function.

       env.ParseFlags(flags, ...)
           Parses one or more strings containing typical command-line flags for GCC-style tool
           chains and returns a dictionary with the flag values separated into the appropriate
           SCons construction variables. Intended as a companion to the env.MergeFlags method,
           but allows for the values in the returned dictionary to be modified, if necessary,
           before merging them into the construction environment. (Note that env.MergeFlags will
           call this method if its argument is not a dictionary, so it is usually not necessary
           to call env.ParseFlags directly unless you want to manipulate the values.)

           If the first character in any string is an exclamation mark (!), the rest of the
           string is executed as a command, and the output from the command is parsed as GCC tool
           chain command-line flags and added to the resulting dictionary. This can be used to
           call a *-config command typical of the POSIX programming environment (for example,
           pkg-config). Note that such a command is executed using the SCons execution
           environment; if the command needs additional information, that information needs to be
           explicitly provided. See ParseConfig for more details.

           Flag values are translated according to the prefix found, and added to the following
           construction variables:

               -arch                   CCFLAGS, LINKFLAGS
               -D                      CPPDEFINES
               -framework              FRAMEWORKS
               -frameworkdir=          FRAMEWORKPATH
               -fmerge-all-constants   CCFLAGS, LINKFLAGS
               -fopenmp                CCFLAGS, LINKFLAGS
               -fsanitize              CCFLAGS, LINKFLAGS
               -include                CCFLAGS
               -imacros                CCFLAGS
               -isysroot               CCFLAGS, LINKFLAGS
               -isystem                CCFLAGS
               -iquote                 CCFLAGS
               -idirafter              CCFLAGS
               -I                      CPPPATH
               -l                      LIBS
               -L                      LIBPATH
               -mno-cygwin             CCFLAGS, LINKFLAGS
               -mwindows               LINKFLAGS
               -openmp                 CCFLAGS, LINKFLAGS
               -pthread                CCFLAGS, LINKFLAGS
               -std=                   CFLAGS
               -Wa,                    ASFLAGS, CCFLAGS
               -Wl,-rpath=             RPATH
               -Wl,-R,                 RPATH
               -Wl,-R                  RPATH
               -Wl,                    LINKFLAGS
               -Wp,                    CPPFLAGS
               -                       CCFLAGS
               +                       CCFLAGS, LINKFLAGS

           Any other strings not associated with options are assumed to be the names of libraries
           and added to the $LIBS construction variable.

           Examples (all of which produce the same result):

               dict = env.ParseFlags('-O2 -Dfoo -Dbar=1')
               dict = env.ParseFlags('-O2', '-Dfoo', '-Dbar=1')
               dict = env.ParseFlags(['-O2', '-Dfoo -Dbar=1'])
               dict = env.ParseFlags('-O2', '!echo -Dfoo -Dbar=1')

       Platform(plat), env.Platform(plat)
           When called as a global function, returns a callable platform object selected by plat
           (defaults to the detected platform for the current system) that can be used to
           initialize a construction environment by passing it as the platform keyword argument
           to the Environment function.

           Example:

               env = Environment(platform=Platform('win32'))

           When called as a method of an environment, calls the platform object indicated by plat
           to update that environment.

               env.Platform('posix')

           See the manpage section "Construction Environments" for more details.

       Precious(target, ...), env.Precious(target, ...)
           Marks each given target as precious so it is not deleted before it is rebuilt.
           Normally scons deletes a target before building it. Multiple targets can be passed in
           to a single call to Precious.

       env.Prepend(key=val, [...])
           Prepend values to construction variables in the current construction environment,
           Works like env.Append (see for details), except that values are added to the front,
           rather than the end, of any existing value of the construction variable

           Example:

               env.Prepend(CCFLAGS='-g ', FOO=['foo.yyy'])

           See also env.Append, env.AppendUnique and env.PrependUnique.

       env.PrependENVPath(name, newpath, [envname, sep, delete_existing=True])
           Prepend path elements specified by newpath to the given search path string or list
           name in mapping envname in the construction environment. Supplying envname is
           optional: the default is the execution environment $ENV. Optional sep is used as the
           search path separator, the default is the platform's separator (os.pathsep). A path
           element will only appear once. Any duplicates in newpath are dropped, keeping the
           first appearing (to preserve path order). If delete_existing is False any addition
           duplicating an existing path element is ignored; if delete_existing is True (the
           default) the existing value will be dropped and the path element will be inserted at
           the beginning. To help maintain uniqueness all paths are normalized (using
           os.path.normpath and os.path.normcase).

           Example:

               print('before:', env['ENV']['INCLUDE'])
               include_path = '/foo/bar:/foo'
               env.PrependENVPath('INCLUDE', include_path)
               print('after:', env['ENV']['INCLUDE'])

           Yields:

               before: /biz:/foo
               after: /foo/bar:/foo:/biz

           See also env.AppendENVPath.

       env.PrependUnique(key=val, [...], [delete_existing=False])
           Prepend values to construction variables in the current construction environment,
           maintaining uniqueness. Works like env.Append, except that values are added to the
           front, rather than the end, of the construction variable, and values that would become
           duplicates are not added. If delete_existing is set to a true value, then for any
           duplicate, the existing instance of val is first removed, then val is inserted, having
           the effect of moving it to the front.

           Example:

               env.PrependUnique(CCFLAGS='-g', FOO=['foo.yyy'])

           See also env.Append, env.AppendUnique and env.Prepend.

       Progress(callable, [interval]), Progress(string, [interval, file, overwrite]),
       Progress(list_of_strings, [interval, file, overwrite])
           Allows SCons to show progress made during the build by displaying a string or calling
           a function while evaluating Nodes (e.g. files).

           If the first specified argument is a Python callable (a function or an object that has
           a __call__ method), the function will be called once every interval times a Node is
           evaluated (default 1). The callable will be passed the evaluated Node as its only
           argument. (For future compatibility, it's a good idea to also add *args and **kwargs
           as arguments to your function or method signatures. This will prevent the code from
           breaking if SCons ever changes the interface to call the function with additional
           arguments in the future.)

           An example of a simple custom progress function that prints a string containing the
           Node name every 10 Nodes:

               def my_progress_function(node, *args, **kwargs):
                   print('Evaluating node %s!' % node)
               Progress(my_progress_function, interval=10)

           A more complicated example of a custom progress display object that prints a string
           containing a count every 100 evaluated Nodes. Note the use of \r (a carriage return)
           at the end so that the string will overwrite itself on a display:

               import sys
               class ProgressCounter(object):
                   count = 0
                   def __call__(self, node, *args, **kw):
                       self.count += 100
                       sys.stderr.write('Evaluated %s nodes\r' % self.count)

               Progress(ProgressCounter(), interval=100)

           If the first argument to Progress is a string or list of strings, it is taken as text
           to be displayed every interval evaluated Nodes. If the first argument is a list of
           strings, then each string in the list will be displayed in rotating fashion every
           interval evaluated Nodes.

           The default is to print the string on standard output. An alternate output stream may
           be specified with the file keyword argument, which the caller must pass already
           opened.

           The following will print a series of dots on the error output, one dot for every 100
           evaluated Nodes:

               import sys
               Progress('.', interval=100, file=sys.stderr)

           If the string contains the verbatim substring $TARGET;, it will be replaced with the
           Node. Note that, for performance reasons, this is not a regular SCons variable
           substition, so you can not use other variables or use curly braces. The following
           example will print the name of every evaluated Node, using a carriage return) (\r) to
           cause each line to overwritten by the next line, and the overwrite keyword argument
           (default False) to make sure the previously-printed file name is overwritten with
           blank spaces:

               import sys
               Progress('$TARGET\r', overwrite=True)

           A list of strings can be used to implement a "spinner" on the user's screen as
           follows, changing every five evaluated Nodes:

               Progress(['-\r', '\\\r', '|\r', '/\r'], interval=5)

       Pseudo(target, ...), env.Pseudo(target, ...)
           This indicates that each given target should not be created by the build rule, and if
           the target is created, an error will be generated. This is similar to the gnu make
           .PHONY target. However, in the vast majority of cases, an Alias is more appropriate.
           Multiple targets can be passed in to a single call to Pseudo.

       PyPackageDir(modulename), env.PyPackageDir(modulename)
           This returns a Directory Node similar to Dir. The python module / package is looked up
           and if located the directory is returned for the location.  modulename Is a named
           python package / module to lookup the directory for it's location.

           If modulename is a list, SCons returns a list of Dir nodes. Construction variables are
           expanded in modulename.

       env.Replace(key=val, [...])
           Replaces construction variables in the Environment with the specified keyword
           arguments.

           Example:

               env.Replace(CCFLAGS='-g', FOO='foo.xxx')

       Repository(directory), env.Repository(directory)
           Specifies that directory is a repository to be searched for files. Multiple calls to
           Repository are legal, and each one adds to the list of repositories that will be
           searched.

           To scons, a repository is a copy of the source tree, from the top-level directory on
           down, which may contain both source files and derived files that can be used to build
           targets in the local source tree. The canonical example would be an official source
           tree maintained by an integrator. If the repository contains derived files, then the
           derived files should have been built using scons, so that the repository contains the
           necessary signature information to allow scons to figure out when it is appropriate to
           use the repository copy of a derived file, instead of building one locally.

           Note that if an up-to-date derived file already exists in a repository, scons will not
           make a copy in the local directory tree. In order to guarantee that a local copy will
           be made, use the Local method.

       Requires(target, prerequisite), env.Requires(target, prerequisite)
           Specifies an order-only relationship between the specified target file(s) and the
           specified prerequisite file(s). The prerequisite file(s) will be (re)built, if
           necessary, before the target file(s), but the target file(s) do not actually depend on
           the prerequisites and will not be rebuilt simply because the prerequisite file(s)
           change.

           Example:

               env.Requires('foo', 'file-that-must-be-built-before-foo')

       Return([vars..., stop=True])
           Return to the calling SConscript, optionally returning the values of variables named
           in vars. Multiple strings contaning variable names may be passed to Return. A string
           containing white space is split into individual variable names. Returns the value if
           one variable is specified, else returns a tuple of values. Returns an empty tuple if
           vars is omitted.

           By default Return stops processing the current SConscript and returns immediately. The
           optional stop keyword argument may be set to a false value to continue processing the
           rest of the SConscript file after the Return call (this was the default behavior prior
           to SCons 0.98.) However, the values returned are still the values of the variables in
           the named vars at the point Return was called.

           Examples:

               # Returns no values (evaluates False)
               Return()

               # Returns the value of the 'foo' Python variable.
               Return("foo")

               # Returns the values of the Python variables 'foo' and 'bar'.
               Return("foo", "bar")

               # Returns the values of Python variables 'val1' and 'val2'.
               Return('val1 val2')

       Scanner(function, [name, argument, skeys, path_function, node_class, node_factory,
       scan_check, recursive]), env.Scanner(function, [name, argument, skeys, path_function,
       node_class, node_factory, scan_check, recursive])
           Creates a Scanner object for the specified function. See manpage section "Scanner
           Objects" for a complete explanation of the arguments and behavior.

       SConscript(scripts, [exports, variant_dir, duplicate, must_exist]),
       env.SConscript(scripts, [exports, variant_dir, duplicate, must_exist]),
       SConscript(dirs=subdirs, [name=scriptname, exports, variant_dir, duplicate, must_exist]),
       env.SConscript(dirs=subdirs, [name=scriptname, exports, variant_dir, duplicate,
       must_exist])
           Executes one or more subsidiary SConscript (configuration) files. There are two ways
           to call the SConscript function.

           The first calling style is to supply one or more SConscript file names as the first
           (positional) argument. A single script may be specified as a string; multiple scripts
           must be specified as a list of strings (either explicitly or as created by a function
           like Split). Examples:

               SConscript('SConscript')  # run SConscript in the current directory
               SConscript('src/SConscript')  # run SConscript in the src directory
               SConscript(['src/SConscript', 'doc/SConscript'])
               config = SConscript('MyConfig.py')

           The other calling style is to omit the positional argument naming scripts and instead
           specify a list of directory names using the dirs keyword argument. In this case, scons
           will execute a subsidiary configuration file named SConscript in each of the specified
           directories. You may specify a name other than SConscript by supplying an optional
           name=scriptname keyword argument. The first three examples below have the same effect
           as the first three examples above:

               SConscript(dirs='.')  # run SConscript in the current directory
               SConscript(dirs='src')  # run SConscript in the src directory
               SConscript(dirs=['src', 'doc'])
               SConscript(dirs=['sub1', 'sub2'], name='MySConscript')

           The optional exports keyword argument provides a string or list of strings
           representing variable names, or a dictionary of named values, to export. For the first
           calling style only, a second positional argument will be interpreted as exports; the
           second calling style must use the keyword argument form for exports. These variables
           are locally exported only to the called SConscript file(s) and do not affect the
           global pool of variables managed by the Export function.  The subsidiary SConscript
           files must use the Import function to import the variables. Examples:

               foo = SConscript('sub/SConscript', exports='env')
               SConscript('dir/SConscript', exports=['env', 'variable'])
               SConscript(dirs='subdir', exports='env variable')
               SConscript(dirs=['one', 'two', 'three'], exports='shared_info')

           If the optional variant_dir argument is present, it causes an effect equivalent to the
           VariantDir function, but in effect only within the scope of the SConscript call. The
           variant_dir argument is interpreted relative to the directory of the calling
           SConscript file. The source directory is the directory in which the called SConscript
           file resides and the SConscript file is evaluated as if it were in the variant_dir
           directory. Thus:

               SConscript('src/SConscript', variant_dir='build')

           is equivalent to:

               VariantDir('build', 'src')
               SConscript('build/SConscript')

           If the sources are in the same directory as the SConstruct,

               SConscript('SConscript', variant_dir='build')

           is equivalent to:

               VariantDir('build', '.')
               SConscript('build/SConscript')

           The optional duplicate argument is interpreted as for VariantDir. If the variant_dir
           argument is omitted, the duplicate argument is ignored. See the description of
           VariantDir for additional details and restrictions.

           If the optional must_exist is True, causes an exception to be raised if a requested
           SConscript file is not found. The current default is False, causing only a warning to
           be emitted, but this default is deprecated (since 3.1). For scripts which truly intend
           to be optional, transition to explicitly supplying must_exist=False to the SConscript
           call.

           Here are some composite examples:

               # collect the configuration information and use it to build src and doc
               shared_info = SConscript('MyConfig.py')
               SConscript('src/SConscript', exports='shared_info')
               SConscript('doc/SConscript', exports='shared_info')

               # build debugging and production versions.  SConscript
               # can use Dir('.').path to determine variant.
               SConscript('SConscript', variant_dir='debug', duplicate=0)
               SConscript('SConscript', variant_dir='prod', duplicate=0)

               # build debugging and production versions.  SConscript
               # is passed flags to use.
               opts = { 'CPPDEFINES' : ['DEBUG'], 'CCFLAGS' : '-pgdb' }
               SConscript('SConscript', variant_dir='debug', duplicate=0, exports=opts)
               opts = { 'CPPDEFINES' : ['NODEBUG'], 'CCFLAGS' : '-O' }
               SConscript('SConscript', variant_dir='prod', duplicate=0, exports=opts)

               # build common documentation and compile for different architectures
               SConscript('doc/SConscript', variant_dir='build/doc', duplicate=0)
               SConscript('src/SConscript', variant_dir='build/x86', duplicate=0)
               SConscript('src/SConscript', variant_dir='build/ppc', duplicate=0)

           SConscript returns the values of any variables named by the executed SConscript
           file(s) in arguments to the Return function. If a single SConscript call causes
           multiple scripts to be executed, the return value is a tuple containing the returns of
           each of the scripts. If an executed script does not explicitly call Return, it returns
           None.

       SConscriptChdir(value)
           By default, scons changes its working directory to the directory in which each
           subsidiary SConscript file lives while reading and processing that script. This
           behavior may be disabled by specifying an argument which evaluates false, in which
           case scons will stay in the top-level directory while reading all SConscript files.
           (This may be necessary when building from repositories, when all the directories in
           which SConscript files may be found don't necessarily exist locally.) You may enable
           and disable this ability by calling SConscriptChdir multiple times.

           Example:

               SConscriptChdir(False)
               SConscript('foo/SConscript')  # will not chdir to foo
               SConscriptChdir(True)
               SConscript('bar/SConscript')  # will chdir to bar

       SConsignFile([name, dbm_module]), env.SConsignFile([name, dbm_module])
           Specify where to store the SCons file signature database, and which database format to
           use. This may be useful to specify alternate database files and/or file locations for
           different types of builds.

           The optional name argument is the base name of the database file(s). If not an
           absolute path name, these are placed relative to the directory containing the
           top-level SConstruct file. The default is .sconsign. The actual database file(s)
           stored on disk may have an appropriate suffix appended by the chosen dbm_module

           The optional dbm_module argument specifies which Python database module to use for
           reading/writing the file. The module must be imported first; then the imported module
           name is passed as the argument. The default is a custom SCons.dblite module that uses
           pickled Python data structures, which works on all Python versions. See documentation
           of the Python dbm module for other available types.

           If called with no arguments, the database will default to .sconsign.dblite in the top
           directory of the project, which is also the default if if SConsignFile is not called.

           The setting is global, so the only difference between the global function and the
           environment method form is variable expansion on name. There should only be one active
           call to this function/method in a given build setup.

           If name is set to None, scons will store file signatures in a separate .sconsign file
           in each directory, not in a single combined database file. This is a
           backwards-compatibility meaure to support what was the default behavior prior to SCons
           0.97 (i.e. before 2008). Use of this mode is discouraged and may be deprecated in a
           future SCons release.

           Examples:

               # Explicitly stores signatures in ".sconsign.dblite"
               # in the top-level SConstruct directory (the default behavior).
               SConsignFile()

               # Stores signatures in the file "etc/scons-signatures"
               # relative to the top-level SConstruct directory.
               # SCons will add a database suffix to this name.
               SConsignFile("etc/scons-signatures")

               # Stores signatures in the specified absolute file name.
               # SCons will add a database suffix to this name.
               SConsignFile("/home/me/SCons/signatures")

               # Stores signatures in a separate .sconsign file
               # in each directory.
               SConsignFile(None)

               # Stores signatures in a GNU dbm format .sconsign file
               import dbm.gnu
               SConsignFile(dbm_module=dbm.gnu)

       env.SetDefault(key=val, [...])
           Sets construction variables to default values specified with the keyword arguments if
           (and only if) the variables are not already set. The following statements are
           equivalent:

               env.SetDefault(FOO='foo')
               if 'FOO' not in env:
                   env['FOO'] = 'foo'

       SetOption(name, value), env.SetOption(name, value)
           Sets scons option variable name to value. These options are all also settable via
           command-line options but the variable name may differ from the command-line option
           name - see the table for correspondences. A value set via command-line option will
           take precedence over one set with SetOption, which allows setting a project default in
           the scripts and temporarily overriding it via command line.  SetOption calls can also
           be placed in the site_init.py file.

           See the documentation in the manpage for the corresponding command line option for
           information about each specific option. The value parameter is mandatory, for option
           values which are boolean in nature (that is, the command line option does not take an
           argument) use a value which evaluates to true (e.g.  True, 1) or false (e.g.  False,
           0).

           Options which affect the reading and processing of SConscript files are not settable
           using SetOption since those files must be read in order to find the SetOption call in
           the first place.

           The settable variables with their associated command-line options are:

           ┌────────────────────────┬───────────────────────────┬──────────────────────────┐
           │Settable name           │ Command-line options      │ Notes                    │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │clean                   │ -c,                       │                          │
           │                        │     --clean,              │                          │
           │                        │     --remove              │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │diskcheck               │ --diskcheck               │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │duplicate               │ --duplicate               │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │experimental            │ --experimental            │ since 4.2                │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │hash_chunksize          │ --hash-chunksize          │ Actually sets            │
           │                        │                           │ md5_chunksize.           │
           │                        │                           │     since 4.2            │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │hash_format             │ --hash-format             │ since 4.2                │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │help                    │ -h, --help                │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │implicit_cache          │ --implicit-cache          │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │implicit_deps_changed   │ --implicit-deps-changed   │ Also sets                │
           │                        │                           │ implicit_cache.          │
           │                        │                           │     (settable since 4.2) │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │implicit_deps_unchanged │ --implicit-deps-unchanged │ Also sets                │
           │                        │                           │ implicit_cache.          │
           │                        │                           │     (settable since 4.2) │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │max_drift               │ --max-drift               │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │md5_chunksize           │ --md5-chunksize           │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │no_exec                 │ -n,                       │                          │
           │                        │     --no-exec,            │                          │
           │                        │     --just-print,         │                          │
           │                        │     --dry-run,            │                          │
           │                        │     --recon               │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │no_progress             │ -Q                        │ See                      │
           │                        │                           │     [6]                  │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │num_jobs                │ -j, --jobs                │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │random                  │ --random                  │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │silent                  │ -s,                       │                          │
           │                        │     --silent,             │                          │
           │                        │     --quiet               │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │stack_size              │ --stack-size              │                          │
           ├────────────────────────┼───────────────────────────┼──────────────────────────┤
           │warn                    │ --warn                    │                          │
           ├────────────────────────┴───────────────────────────┴──────────────────────────┤
           │----                                                                           │
           │[a] If no_progress is set via SetOption in an SConscript file (but not if      │
           │set in a site_init.py file) there will still be an initial status message      │
           │about reading SConscript files since SCons has to start reading them           │
           │before it can see the SetOption.                                               │
           └───────────────────────────────────────────────────────────────────────────────┘
           Example:

               SetOption('max_drift', 0)

       SideEffect(side_effect, target), env.SideEffect(side_effect, target)
           Declares side_effect as a side effect of building target. Both side_effect and target
           can be a list, a file name, or a node. A side effect is a target file that is created
           or updated as a side effect of building other targets. For example, a Windows PDB file
           is created as a side effect of building the .obj files for a static library, and
           various log files are created updated as side effects of various TeX commands. If a
           target is a side effect of multiple build commands, scons will ensure that only one
           set of commands is executed at a time. Consequently, you only need to use this method
           for side-effect targets that are built as a result of multiple build commands.

           Because multiple build commands may update the same side effect file, by default the
           side_effect target is not automatically removed when the target is removed by the -c
           option. (Note, however, that the side_effect might be removed as part of cleaning the
           directory in which it lives.) If you want to make sure the side_effect is cleaned
           whenever a specific target is cleaned, you must specify this explicitly with the Clean
           or env.Clean function.

           This function returns the list of side effect Node objects that were successfully
           added. If the list of side effects contained any side effects that had already been
           added, they are not added and included in the returned list.

       Split(arg), env.Split(arg)
           If arg is a string, splits on whitespace and returns a list of strings without
           whitespace. This mode is the most common case, and can be used to split a list of
           filenames (for example) rather than having to type them as a list of individually
           quoted words. If arg is a list or tuple returns the list or tuple unchanged. If arg is
           any other type of object, returns a list containing just the object. These non-string
           cases do not actually do any spliting, but allow an argument variable to be passed to
           Split without having to first check its type.

           Example:

               files = Split("f1.c f2.c f3.c")
               files = env.Split("f4.c f5.c f6.c")
               files = Split("""
                   f7.c
                   f8.c
                   f9.c
               """)

       env.subst(input, [raw, target, source, conv])
           Performs construction variable interpolation (substitution) on input, which can be a
           string or a sequence. Substitutable elements take the form ${expression}, although if
           there is no ambiguity in recognizing the element, the braces can be omitted. A literal
           $ can be entered by using $$.

           By default, leading or trailing white space will be removed from the result, and all
           sequences of white space will be compressed to a single space character. Additionally,
           any $( and $) character sequences will be stripped from the returned string, The
           optional raw argument may be set to 1 if you want to preserve white space and $(-$)
           sequences. The raw argument may be set to 2 if you want to additionally discard all
           characters between any $( and $) pairs (as is done for signature calculation).

           If input is a sequence (list or tuple), the individual elements of the sequence will
           be expanded, and the results will be returned as a list.

           The optional target and source keyword arguments must be set to lists of target and
           source nodes, respectively, if you want the $TARGET, $TARGETS, $SOURCE and $SOURCES to
           be available for expansion. This is usually necessary if you are calling env.subst
           from within a Python function used as an SCons action.

           Returned string values or sequence elements are converted to their string
           representation by default. The optional conv argument may specify a conversion
           function that will be used in place of the default. For example, if you want Python
           objects (including SCons Nodes) to be returned as Python objects, you can use a Python
           lambda expression to pass in an unnamed function that simply returns its unconverted
           argument.

           Example:

               print(env.subst("The C compiler is: $CC"))

               def compile(target, source, env):
                   sourceDir = env.subst(
                       "${SOURCE.srcdir}",
                       target=target,
                       source=source
                   )

               source_nodes = env.subst('$EXPAND_TO_NODELIST', conv=lambda x: x)

       Tag(node, tags)
           Annotates file or directory Nodes with information about how the Package Builder
           should package those files or directories. All Node-level tags are optional.

           Examples:

               # makes sure the built library will be installed with 644 file access mode
               Tag(Library('lib.c'), UNIX_ATTR="0o644")

               # marks file2.txt to be a documentation file
               Tag('file2.txt', DOC)

       Tool(name, [toolpath, **kwargs]), env.Tool(name, [toolpath, **kwargs])
           Locates the tool specification module name and returns a callable tool object for that
           tool. The tool module is searched for in standard locations and in any paths specified
           by the optional toolpath parameter. The standard locations are SCons' own internal
           path for tools plus the toolpath, if any (see the Tools section in the manual page for
           more details). Any additional keyword arguments kwargs are passed to the tool module's
           generate function during tool object construction.

           When called, the tool object updates a construction environment with construction
           variables and arranges any other initialization needed to use the mechanisms that tool
           describes.

           When the env.Tool form is used, the tool object is automatically called to update env
           and the value of tool is appended to the $TOOLS construction variable in that
           environment.

           Changed in version 4.2: env.Tool now returns the tool object, previously it did not
           return (i.e. returned None).

           Examples:

               env.Tool('gcc')
               env.Tool('opengl', toolpath=['build/tools'])

           When the global function Tool form is used, the tool object is constructed but not
           called, as it lacks the context of an environment to update. The tool object can be
           passed to an Environment or Clone call as part of the tools keyword argument, in which
           case the tool is applied to the environment being constructed, or it can be called
           directly, in which case a construction environment to update must be passed as the
           argument. Either approach will also update the $TOOLS construction variable.

           Examples:

               env = Environment(tools=[Tool('msvc')])

               env = Environment()
               msvctool = Tool('msvc')
               msvctool(env)  # adds 'msvc' to the TOOLS variable
               gltool = Tool('opengl', toolpath = ['tools'])
               gltool(env)  # adds 'opengl' to the TOOLS variable

       ValidateOptions([throw_exception=False])
           Check that all the options specified on the command line are either defined by SCons
           itself or defined by calls to AddOption.

           This function should only be called after the last AddOption call in your SConscript
           logic.

           Be aware that some tools call AddOption, if you are getting error messages for
           arguments that they add, you will need to ensure that you load those tools before you
           call ValidateOptions.

           If there are any command line options not defined, calling this function will cause
           SCons to issue an error message and then exit with an error exit status.

           If the optional throw_exception is True, ValidateOptions will raise a
           SConsBadOptionError exception. This would allow the calling SConscript logic can catch
           that exception and handle invalid options itself.

           Example:

               try:
                   ValidateOptions(throw_exception=True)
               except SConsBadOptionError as e:
                   print("Parser is SConsOptionParser:%s" % (isinstance(e.parser, SConsOptionParser)))
                   print("Message is :%s" % e.opt_str)
                   Exit(3)

           This function is useful to force SCons to fail fast before you execute any expensive
           logic later in your build logic. For example if you specify build options via any
           flags, a simple typo could yield the incorrect build option throughout your entire
           build.

               scons --compilers=mingw (the correct flag is --compiler)

           Could cause SCons to run configure steps with the incorrect compiler. Costing
           developer time trying to track down why the configure logic failed with a compiler
           which should work.

           New in version 4.5.0

       Value(value, [built_value], [name]), env.Value(value, [built_value], [name])
           Returns a Node object representing the specified Python value. Value Nodes can be used
           as dependencies of targets. If the result of calling str(value) changes between SCons
           runs, any targets depending on Value(value) will be rebuilt. (This is true even when
           using timestamps to decide if files are up-to-date.) When using timestamp source
           signatures, Value Nodes' timestamps are equal to the system time when the Node is
           created.

           The returned Value Node object has a write() method that can be used to "build" a
           Value Node by setting a new value. The optional built_value argument can be specified
           when the Value Node is created to indicate the Node should already be considered
           "built." There is a corresponding read() method that will return the built value of
           the Node.

           The optional name parameter can be provided as an alternative name for the resulting
           Value node; this is advised if the value parameter cannot be converted to a string.

           Changed in version 4.0: the name parameter was added.

           Examples:

               env = Environment()

               def create(target, source, env):
                   # A function that will write a 'prefix=$SOURCE'
                   # string into the file name specified as the
                   # $TARGET.
                   with open(str(target[0]), 'wb') as f:
                       f.write('prefix=' + source[0].get_contents())

               # Fetch the prefix= argument, if any, from the command
               # line, and use /usr/local as the default.
               prefix = ARGUMENTS.get('prefix', '/usr/local')

               # Attach a .Config() builder for the above function action
               # to the construction environment.
               env['BUILDERS']['Config'] = Builder(action=create)
               env.Config(target='package-config', source=Value(prefix))

               def build_value(target, source, env):
                   # A function that "builds" a Python Value by updating
                   # the Python value with the contents of the file
                   # specified as the source of the Builder call ($SOURCE).
                   target[0].write(source[0].get_contents())

               output = env.Value('before')
               input = env.Value('after')

               # Attach a .UpdateValue() builder for the above function
               # action to the construction environment.
               env['BUILDERS']['UpdateValue'] = Builder(action=build_value)
               env.UpdateValue(target=Value(output), source=Value(input))

       VariantDir(variant_dir, src_dir, [duplicate]), env.VariantDir(variant_dir, src_dir,
       [duplicate])
           Sets up a mapping to define a variant build directory in variant_dir.  src_dir may not
           be underneath variant_dir. A VariantDir mapping is global, even if called using the
           env.VariantDir form.  VariantDir can be called multiple times with the same src_dir to
           set up multiple variant builds with different options.

           Note if variant_dir is not under the project top directory, target selection rules
           will not pick targets in the variant directory unless they are explicitly specified.

           When files in variant_dir are referenced, SCons backfills as needed with files from
           src_dir to create a complete build directory. By default, SCons physically duplicates
           the source files, SConscript files, and directory structure as needed into the variant
           directory. Thus, a build performed in the variant directory is guaranteed to be
           identical to a build performed in the source directory even if intermediate source
           files are generated during the build, or if preprocessors or other scanners search for
           included files using paths relative to the source file, or if individual compilers or
           other invoked tools are hard-coded to put derived files in the same directory as
           source files. Only the files SCons calculates are needed for the build are duplicated
           into variant_dir. If possible on the platform, the duplication is performed by linking
           rather than copying. This behavior is affected by the --duplicate command-line option.

           Duplicating the source files may be disabled by setting the duplicate argument to
           False. This will cause SCons to invoke Builders using the path names of source files
           in src_dir and the path names of derived files within variant_dir. This is more
           efficient than duplicating, and is safe for most builds; revert to duplicate=True if
           it causes problems.

           VariantDir works most naturally when used with a subsidiary SConscript file. The
           subsidiary SConscript file must be called as if it were in variant_dir, regardless of
           the value of duplicate. When calling an SConscript file, you can use the exports
           keyword argument to pass parameters (individually or as an appropriately set up
           environment) so the SConscript can pick up the right settings for that variant build.
           The SConscript must Import these to use them. Example:

               env1 = Environment(...settings for variant1...)
               env2 = Environment(...settings for variant2...)

               # run src/SConscript in two variant directories
               VariantDir('build/variant1', 'src')
               SConscript('build/variant1/SConscript', exports={"env": env1})
               VariantDir('build/variant2', 'src')
               SConscript('build/variant2/SConscript', exports={"env": env2})

           See also the SConscript function for another way to specify a variant directory in
           conjunction with calling a subsidiary SConscript file.

           More examples:

               # use names in the build directory, not the source directory
               VariantDir('build', 'src', duplicate=0)
               Program('build/prog', 'build/source.c')

               # this builds both the source and docs in a separate subtree
               VariantDir('build', '.', duplicate=0)
               SConscript(dirs=['build/src','build/doc'])

               # same as previous example, but only uses SConscript
               SConscript(dirs='src', variant_dir='build/src', duplicate=0)
               SConscript(dirs='doc', variant_dir='build/doc', duplicate=0)

       WhereIs(program, [path, pathext, reject]), env.WhereIs(program, [path, pathext, reject])
           Searches for the specified executable program, returning the full path to the program
           or None.

           When called as a construction environment method, searches the paths in the path
           keyword argument, or if None (the default) the paths listed in the construction
           environment (env['ENV']['PATH']). The external environment's path list
           (os.environ['PATH']) is used as a fallback if the key env['ENV']['PATH'] does not
           exist.

           On Windows systems, searches for executable programs with any of the file extensions
           listed in the pathext keyword argument, or if None (the default) the pathname
           extensions listed in the construction environment (env['ENV']['PATHEXT']). The
           external environment's pathname extensions list (os.environ['PATHEXT']) is used as a
           fallback if the key env['ENV']['PATHEXT'] does not exist.

           When called as a global function, uses the external environment's path
           os.environ['PATH'] and path extensions os.environ['PATHEXT'], respectively, if path
           and pathext are None.

           Will not select any path name or names in the optional reject list.

   SConscript Variables
       In addition to the global functions and methods, scons supports a number of variables that
       can be used in SConscript files to affect how you want the build to be performed.

       ARGLIST
           A list of the keyword=value arguments specified on the command line. Each element in
           the list is a tuple containing the argument. The separate keyword and value elements
           of the tuple can be accessed by subscripting for elements [0] and [1] of the tuple,
           or, more readably, by using tuple unpacking. Example:

               print("first keyword, value =", ARGLIST[0][0], ARGLIST[0][1])
               print("second keyword, value =", ARGLIST[1][0], ARGLIST[1][1])
               key, value = ARGLIST[2]
               print("third keyword, value =", key, value)
               for key, value in ARGLIST:
                   # process key and value

       ARGUMENTS
           A dictionary of all the keyword=value arguments specified on the command line. The
           dictionary is not in order, and if a given keyword has more than one value assigned to
           it on the command line, the last (right-most) value is the one in the ARGUMENTS
           dictionary.

           Example:

               if ARGUMENTS.get('debug', 0):
                   env = Environment(CCFLAGS='-g')
               else:
                   env = Environment()

       BUILD_TARGETS
           A list of the targets which scons has been asked to build. The contents will be either
           those targets listed on the command line, or, if none, those targets set via calls to
           the Default function. It does not contain any dependent targets that scons selects for
           building as a result of making the sure the specified targets are up to date, if those
           targets did not appear on the command line. The list is empty if neither command line
           targets or Default calls are present.

           The elements of this list may be strings or nodes, so you should run the list through
           the Python str function to make sure any Node path names are converted to strings.

           Because this list may be taken from the list of targets specified using the Default
           function, the contents of the list may change on each successive call to Default. See
           the DEFAULT_TARGETS list, below, for additional information.

           Example:

               if 'foo' in BUILD_TARGETS:
                   print("Don't forget to test the `foo' program!")
               if 'special/program' in BUILD_TARGETS:
                   SConscript('special')

       COMMAND_LINE_TARGETS
           A list of the targets explicitly specified on the command line. If there are command
           line targets, this list will have the same contents as BUILD_TARGETS. If there are no
           targets specified on the command line, the list is empty. The elements of this list
           are strings. This can be used, for example, to take specific actions only when certain
           targets are explicitly being built.

           Example:

               if 'foo' in COMMAND_LINE_TARGETS:
                   print("Don't forget to test the `foo' program!")
               if 'special/program' in COMMAND_LINE_TARGETS:
                   SConscript('special')

       DEFAULT_TARGETS
           A list of the target nodes that have been specified using the Default function. If
           there are no command line targets, this list will have the same contents as
           BUILD_TARGETS. Since the elements of the list are nodes, you need to call the Python
           str function on them to get the path name for each Node.

           Example:

               print(str(DEFAULT_TARGETS[0]))
               if 'foo' in [str(t) for t in DEFAULT_TARGETS]:
                   print("Don't forget to test the `foo' program!")

           The contents of the DEFAULT_TARGETS list change on on each successive call to the
           Default function:

               print([str(t) for t in DEFAULT_TARGETS])   # originally []
               Default('foo')
               print([str(t) for t in DEFAULT_TARGETS])   # now a node ['foo']
               Default('bar')
               print([str(t) for t in DEFAULT_TARGETS])   # now a node ['foo', 'bar']
               Default(None)
               print([str(t) for t in DEFAULT_TARGETS])   # back to []

           Consequently, be sure to use DEFAULT_TARGETS only after you've made all of your
           Default() calls, or else simply be careful of the order of these statements in your
           SConscript files so that you don't look for a specific default target before it's
           actually been added to the list.

       These variables may be accessed from custom Python modules that you import into an
       SConscript file by adding the following to the Python module:

           from SCons.Script import *

   Construction Variables
       A construction environment has an associated dictionary of construction variables that are
       used by built-in or user-supplied build rules.  Construction variable naming must follow
       the same rules as Python identifier naming: the initial character must be an underscore or
       letter, followed by any number of underscores, letters, or digits. A construction
       environment is not a Python dictionary itself, but it can be indexed like one to access a
       construction variable:

           env["CC"] = "cc"
           flags = env.get("CPPDEFINES", [])

       Construction variables can also be retrieved and set by using the Dictionary method of the
       construction environment to create an actual dictionary:

           cvars = env.Dictionary()
           cvars["CC"] = "cc"

       Construction variables can also be passed to the construction environment constructor:

           env = Environment(CC="cc")

       or when copying a construction environment using the Clone method:

           env2 = env.Clone(CC="cl.exe")

       Construction variables can also be supplied as keyword arguments to a builder, in which
       case those settings affect only the work done by that builder call, and not the
       construction environment as a whole. This concept is called an override:

           env.Program('hello', 'hello.c', LIBS=['gl', 'glut'])

       A number of useful construction variables are automatically defined by scons for each
       supported platform, and you can modify these or define any additional construction
       variables for your own use, taking care not to overwrite ones which SCons is using. The
       following is a list of the possible automatically defined construction variables.

       Note the actual list available at execution time will never include all of these, as the
       ones detected as not being useful (wrong platform, necessary external command or files not
       installed, etc.) will not be set up. Correct build setups should be resilient to the
       possible absence of certain construction variables before using them, for example by using
       a Python dictionary get method to retrieve the value and taking alternative action if the
       return indicates the variable is unset. The env.Dump method can be called to examine the
       construction variables set in a particular environment.

       __LDMODULEVERSIONFLAGS
           This construction variable automatically introduces $_LDMODULEVERSIONFLAGS if
           $LDMODULEVERSION is set. Othervise it evaluates to an empty string.

       __SHLIBVERSIONFLAGS
           This construction variable automatically introduces $_SHLIBVERSIONFLAGS if
           $SHLIBVERSION is set. Othervise it evaluates to an empty string.

       APPLELINK_COMPATIBILITY_VERSION
           On Mac OS X this is used to set the linker flag: -compatibility_version

           The value is specified as X[.Y[.Z]] where X is between 1 and 65535, Y can be omitted
           or between 1 and 255, Z can be omitted or between 1 and 255. This value will be
           derived from $SHLIBVERSION if not specified. The lowest digit will be dropped and
           replaced by a 0.

           If the $APPLELINK_NO_COMPATIBILITY_VERSION is set then no -compatibility_version will
           be output.

           See MacOS's ld manpage for more details

       _APPLELINK_COMPATIBILITY_VERSION
           A macro (by default a generator function) used to create the linker flags to specify
           apple's linker's -compatibility_version flag. The default generator uses
           $APPLELINK_COMPATIBILITY_VERSION and $APPLELINK_NO_COMPATIBILITY_VERSION and
           $SHLIBVERSION to determine the correct flag.

       APPLELINK_CURRENT_VERSION
           On Mac OS X this is used to set the linker flag: -current_version

           The value is specified as X[.Y[.Z]] where X is between 1 and 65535, Y can be omitted
           or between 1 and 255, Z can be omitted or between 1 and 255. This value will be set to
           $SHLIBVERSION if not specified.

           If the $APPLELINK_NO_CURRENT_VERSION is set then no -current_version will be output.

           See MacOS's ld manpage for more details

       _APPLELINK_CURRENT_VERSION
           A macro (by default a generator function) used to create the linker flags to specify
           apple's linker's -current_version flag. The default generator uses
           $APPLELINK_CURRENT_VERSION and $APPLELINK_NO_CURRENT_VERSION and $SHLIBVERSION to
           determine the correct flag.

       APPLELINK_NO_COMPATIBILITY_VERSION
           Set this to any True (1|True|non-empty string) value to disable adding
           -compatibility_version flag when generating versioned shared libraries.

           This overrides $APPLELINK_COMPATIBILITY_VERSION.

       APPLELINK_NO_CURRENT_VERSION
           Set this to any True (1|True|non-empty string) value to disable adding
           -current_version flag when generating versioned shared libraries.

           This overrides $APPLELINK_CURRENT_VERSION.

       AR
           The static library archiver.

       ARCHITECTURE
           Specifies the system architecture for which the package is being built. The default is
           the system architecture of the machine on which SCons is running. This is used to fill
           in the Architecture: field in an Ipkg control file, and the BuildArch: field in the
           RPM .spec file, as well as forming part of the name of a generated RPM package file.

           See the Package builder.

       ARCOM
           The command line used to generate a static library from object files.

       ARCOMSTR
           The string displayed when a static library is generated from object files. If this is
           not set, then $ARCOM (the command line) is displayed.

               env = Environment(ARCOMSTR = "Archiving $TARGET")

       ARFLAGS
           General options passed to the static library archiver.

       AS
           The assembler.

       ASCOM
           The command line used to generate an object file from an assembly-language source
           file.

       ASCOMSTR
           The string displayed when an object file is generated from an assembly-language source
           file. If this is not set, then $ASCOM (the command line) is displayed.

               env = Environment(ASCOMSTR = "Assembling $TARGET")

       ASFLAGS
           General options passed to the assembler.

       ASPPCOM
           The command line used to assemble an assembly-language source file into an object file
           after first running the file through the C preprocessor. Any options specified in the
           $ASFLAGS and $CPPFLAGS construction variables are included on this command line.

       ASPPCOMSTR
           The string displayed when an object file is generated from an assembly-language source
           file after first running the file through the C preprocessor. If this is not set, then
           $ASPPCOM (the command line) is displayed.

               env = Environment(ASPPCOMSTR = "Assembling $TARGET")

       ASPPFLAGS
           General options when an assembling an assembly-language source file into an object
           file after first running the file through the C preprocessor. The default is to use
           the value of $ASFLAGS.

       BIBTEX
           The bibliography generator for the TeX formatter and typesetter and the LaTeX
           structured formatter and typesetter.

       BIBTEXCOM
           The command line used to call the bibliography generator for the TeX formatter and
           typesetter and the LaTeX structured formatter and typesetter.

       BIBTEXCOMSTR
           The string displayed when generating a bibliography for TeX or LaTeX. If this is not
           set, then $BIBTEXCOM (the command line) is displayed.

               env = Environment(BIBTEXCOMSTR = "Generating bibliography $TARGET")

       BIBTEXFLAGS
           General options passed to the bibliography generator for the TeX formatter and
           typesetter and the LaTeX structured formatter and typesetter.

       BUILDERS
           A dictionary mapping the names of the builders available through the construction
           environment to underlying Builder objects. Custom builders need to be added to this to
           make them available.

           A platform-dependent default list of builders such as Program, Library etc. is used to
           populate this construction variable when the construction environment is initialized
           via the presence/absence of the tools those builders depend on.  $BUILDERS can be
           examined to learn which builders will actually be available at run-time.

           Note that if you initialize this construction variable through assignment when the
           construction environment is created, that value for $BUILDERS will override any
           defaults:

               bld = Builder(action='foobuild < $SOURCE > $TARGET')
               env = Environment(BUILDERS={'NewBuilder': bld})

           To instead use a new Builder object in addition to the default Builders, add your new
           Builder object like this:

               env = Environment()
               env.Append(BUILDERS={'NewBuilder': bld})

           or this:

               env = Environment()
               env['BUILDERS']['NewBuilder'] = bld

       CACHEDIR_CLASS
           The class type that SCons should use when instantiating a new CacheDir for the given
           environment. It must be a subclass of the SCons.CacheDir.CacheDir class.

       CC
           The C compiler.

       CCCOM
           The command line used to compile a C source file to a (static) object file. Any
           options specified in the $CFLAGS, $CCFLAGS and $CPPFLAGS construction variables are
           included on this command line. See also $SHCCCOM for compiling to shared objects.

       CCCOMSTR
           If set, the string displayed when a C source file is compiled to a (static) object
           file. If not set, then $CCCOM (the command line) is displayed. See also $SHCCCOMSTR
           for compiling to shared objects.

               env = Environment(CCCOMSTR = "Compiling static object $TARGET")

       CCDEPFLAGS
           Options to pass to C or C++ compiler to generate list of dependency files.

           This is set only by compilers which support this functionality. (gcc, clang, and msvc
           currently)

       CCFLAGS
           General options that are passed to the C and C++ compilers. See also $SHCCFLAGS for
           compiling to shared objects.

       CCPCHFLAGS
           Options added to the compiler command line to support building with precompiled
           headers. The default value expands expands to the appropriate Microsoft Visual C++
           command-line options when the $PCH construction variable is set.

       CCPDBFLAGS
           Options added to the compiler command line to support storing debugging information in
           a Microsoft Visual C++ PDB file. The default value expands expands to appropriate
           Microsoft Visual C++ command-line options when the $PDB construction variable is set.

           The Visual C++ compiler option that SCons uses by default to generate PDB information
           is /Z7. This works correctly with parallel (-j) builds because it embeds the debug
           information in the intermediate object files, as opposed to sharing a single PDB file
           between multiple object files. This is also the only way to get debug information
           embedded into a static library. Using the /Zi instead may yield improved link-time
           performance, although parallel builds will no longer work.

           You can generate PDB files with the /Zi switch by overriding the default $CCPDBFLAGS
           variable as follows:

               env['CCPDBFLAGS'] = ['${(PDB and "/Zi /Fd%s" % File(PDB)) or ""}']

           An alternative would be to use the /Zi to put the debugging information in a separate
           .pdb file for each object file by overriding the $CCPDBFLAGS variable as follows:

               env['CCPDBFLAGS'] = '/Zi /Fd${TARGET}.pdb'

       CCVERSION
           The version number of the C compiler. This may or may not be set, depending on the
           specific C compiler being used.

       CFILESUFFIX
           The suffix for C source files. This is used by the internal CFile builder when
           generating C files from Lex (.l) or YACC (.y) input files. The default suffix, of
           course, is .c (lower case). On case-insensitive systems (like Windows), SCons also
           treats .C (upper case) files as C files.

       CFLAGS
           General options that are passed to the C compiler (C only; not C++). See also
           $SHCFLAGS for compiling to shared objects.

       CHANGE_SPECFILE
           A hook for modifying the file that controls the packaging build (the .spec for RPM,
           the control for Ipkg, the .wxs for MSI). If set, the function will be called after the
           SCons template for the file has been written.

           See the Package builder.

       CHANGED_SOURCES
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       CHANGED_TARGETS
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       CHANGELOG
           The name of a file containing the change log text to be included in the package. This
           is included as the %changelog section of the RPM .spec file.

           See the Package builder.

       COMPILATIONDB_COMSTR
           The string displayed when the CompilationDatabase builder's action is run.

       COMPILATIONDB_PATH_FILTER
           A string which instructs CompilationDatabase to only include entries where the output
           member matches the pattern in the filter string using fnmatch, which uses glob style
           wildcards.

           The default value is an empty string '', which disables filtering.

       COMPILATIONDB_USE_ABSPATH
           A boolean flag to instruct CompilationDatabase whether to write the file and output
           members in the compilation database using absolute or relative paths.

           The default value is False (use relative paths)

       _concat
           A function used to produce variables like $_CPPINCFLAGS. It takes four mandatory
           arguments, and up to 4 additional optional arguments: 1) a prefix to concatenate onto
           each element, 2) a list of elements, 3) a suffix to concatenate onto each element, 4)
           an environment for variable interpolation, 5) an optional function that will be called
           to transform the list before concatenation, 6) an optionally specified target (Can use
           TARGET), 7) an optionally specified source (Can use SOURCE), 8) optional
           affect_signature flag which will wrap non-empty returned value with $( and $) to
           indicate the contents should not affect the signature of the generated command line.

                       env['_CPPINCFLAGS'] = '${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs, TARGET, SOURCE, affect_signature=False)}'

       CONFIGUREDIR
           The name of the directory in which Configure context test files are written. The
           default is .sconf_temp in the top-level directory containing the SConstruct file.

       CONFIGURELOG
           The name of the Configure context log file. The default is config.log in the top-level
           directory containing the SConstruct file.

       _CPPDEFFLAGS
           An automatically-generated construction variable containing the C preprocessor
           command-line options to define values. The value of $_CPPDEFFLAGS is created by
           respectively prepending and appending $CPPDEFPREFIX and $CPPDEFSUFFIX to each
           definition in $CPPDEFINES.

       CPPDEFINES
           A platform independent specification of C preprocessor macro definitions. The
           definitions are added to command lines through the automatically-generated
           $_CPPDEFFLAGS construction variable, which is constructed according to the contents of
           $CPPDEFINES:

           •   If $CPPDEFINES is a string, the values of the $CPPDEFPREFIX and $CPPDEFSUFFIX
               construction variables are respectively prepended and appended to each definition
               in $CPPDEFINES, split on whitespace.

                   # Adds -Dxyz to POSIX compiler command lines,
                   # and /Dxyz to Microsoft Visual C++ command lines.
                   env = Environment(CPPDEFINES='xyz')

           •   If $CPPDEFINES is a list, the values of the $CPPDEFPREFIX and $CPPDEFSUFFIX
               construction variables are respectively prepended and appended to each element in
               the list. If any element is a tuple (or list) then the first item of the tuple is
               the macro name and the second is the macro definition. If the definition is not
               omitted or None, the name and definition are combined into a single
               name=definition item before the preending/appending.

                   # Adds -DB=2 -DA to POSIX compiler command lines,
                   # and /DB=2 /DA to Microsoft Visual C++ command lines.
                   env = Environment(CPPDEFINES=[('B', 2), 'A'])

           •   If $CPPDEFINES is a dictionary, the values of the $CPPDEFPREFIX and $CPPDEFSUFFIX
               construction variables are respectively prepended and appended to each key from
               the dictionary. If the value for a key is not None, then the key (macro name) and
               the value (macros definition) are combined into a single name=definition item
               before the prepending/appending.

                   # Adds -DA -DB=2 to POSIX compiler command lines,
                   # or /DA /DB=2 to Microsoft Visual C++ command lines.
                   env = Environment(CPPDEFINES={'B':2, 'A':None})

           Depending on how contents are added to $CPPDEFINES, it may be transformed into a
           compound type, for example a list containing strings, tuples and/or dictionaries.
           SCons can correctly expand such a compound type.

           Note that SCons may call the compiler via a shell. If a macro definition contains
           characters such as spaces that have meaning to the shell, or is intended to be a
           string value, you may need to use the shell's quoting syntax to avoid interpretation
           by the shell before the preprocessor sees it. Function-like macros are not supported
           via this mechanism (and some compilers do not even implement that functionality via
           the command lines). When quoting, note that one set of quote characters are used to
           define a Python string, then quotes embedded inside that would be consumed by the
           shell unless escaped. These examples may help illustrate:

               env = Environment(CPPDEFINES=['USE_ALT_HEADER=\\"foo_alt.h\\"'])
               env = Environment(CPPDEFINES=[('USE_ALT_HEADER', '\\"foo_alt.h\\"')])

           :Changed in version 4.5: SCons no longer sorts $CPPDEFINES values entered in
           dictionary form.  Python now preserves dictionary keys in the order they are entered,
           so it is no longer necessary to sort them to ensure a stable command line.

       CPPDEFPREFIX
           The prefix used to specify preprocessor macro definitions on the C compiler command
           line. This will be prepended to each definition in the $CPPDEFINES construction
           variable when the $_CPPDEFFLAGS variable is automatically generated.

       CPPDEFSUFFIX
           The suffix used to specify preprocessor macro definitions on the C compiler command
           line. This will be appended to each definition in the $CPPDEFINES construction
           variable when the $_CPPDEFFLAGS variable is automatically generated.

       CPPFLAGS
           User-specified C preprocessor options. These will be included in any command that uses
           the C preprocessor, including not just compilation of C and C++ source files via the
           $CCCOM, $SHCCCOM, $CXXCOM and $SHCXXCOM command lines, but also the $FORTRANPPCOM,
           $SHFORTRANPPCOM, $F77PPCOM and $SHF77PPCOM command lines used to compile a Fortran
           source file, and the $ASPPCOM command line used to assemble an assembly language
           source file, after first running each file through the C preprocessor. Note that this
           variable does not contain -I (or similar) include search path options that scons
           generates automatically from $CPPPATH. See $_CPPINCFLAGS, below, for the variable that
           expands to those options.

       _CPPINCFLAGS
           An automatically-generated construction variable containing the C preprocessor
           command-line options for specifying directories to be searched for include files. The
           value of $_CPPINCFLAGS is created by respectively prepending and appending $INCPREFIX
           and $INCSUFFIX to each directory in $CPPPATH.

       CPPPATH
           The list of directories that the C preprocessor will search for include directories.
           The C/C++ implicit dependency scanner will search these directories for include files.
           In general it's not advised to put include directory directives directly into $CCFLAGS
           or $CXXFLAGS as the result will be non-portable and the directories will not be
           searched by the dependency scanner.  $CPPPATH should be a list of path strings, or a
           single string, not a pathname list joined by Python's os.sep.

           Note: directory names in $CPPPATH will be looked-up relative to the directory of the
           SConscript file when they are used in a command. To force scons to look-up a directory
           relative to the root of the source tree use the # prefix:

               env = Environment(CPPPATH='#/include')

           The directory look-up can also be forced using the Dir function:

               include = Dir('include')
               env = Environment(CPPPATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_CPPINCFLAGS construction variable, which is constructed by respectively prepending
           and appending the values of the $INCPREFIX and $INCSUFFIX construction variables to
           each directory in $CPPPATH. Any command lines you define that need the $CPPPATH
           directory list should include $_CPPINCFLAGS:

               env = Environment(CCCOM="my_compiler $_CPPINCFLAGS -c -o $TARGET $SOURCE")

       CPPSUFFIXES
           The list of suffixes of files that will be scanned for C preprocessor implicit
           dependencies (#include lines). The default list is:

               [".c", ".C", ".cxx", ".cpp", ".c++", ".cc",
                ".h", ".H", ".hxx", ".hpp", ".hh",
                ".F", ".fpp", ".FPP",
                ".m", ".mm",
                ".S", ".spp", ".SPP"]

       CXX
           The C++ compiler. See also $SHCXX for compiling to shared objects..

       CXXCOM
           The command line used to compile a C++ source file to an object file. Any options
           specified in the $CXXFLAGS and $CPPFLAGS construction variables are included on this
           command line. See also $SHCXXCOM for compiling to shared objects..

       CXXCOMSTR
           If set, the string displayed when a C++ source file is compiled to a (static) object
           file. If not set, then $CXXCOM (the command line) is displayed. See also $SHCXXCOMSTR
           for compiling to shared objects..

               env = Environment(CXXCOMSTR = "Compiling static object $TARGET")

       CXXFILESUFFIX
           The suffix for C++ source files. This is used by the internal CXXFile builder when
           generating C++ files from Lex (.ll) or YACC (.yy) input files. The default suffix is
           .cc. SCons also treats files with the suffixes .cpp, .cxx, .c++, and .C++ as C++
           files, and files with .mm suffixes as Objective C++ files. On case-sensitive systems
           (Linux, UNIX, and other POSIX-alikes), SCons also treats .C (upper case) files as C++
           files.

       CXXFLAGS
           General options that are passed to the C++ compiler. By default, this includes the
           value of $CCFLAGS, so that setting $CCFLAGS affects both C and C++ compilation. If you
           want to add C++-specific flags, you must set or override the value of $CXXFLAGS. See
           also $SHCXXFLAGS for compiling to shared objects..

       CXXVERSION
           The version number of the C++ compiler. This may or may not be set, depending on the
           specific C++ compiler being used.

       DC
           The D compiler to use. See also $SHDC for compiling to shared objects.

       DCOM
           The command line used to compile a D file to an object file. Any options specified in
           the $DFLAGS construction variable is included on this command line. See also $SHDCOM
           for compiling to shared objects.

       DCOMSTR
           If set, the string displayed when a D source file is compiled to a (static) object
           file. If not set, then $DCOM (the command line) is displayed. See also $SHDCOMSTR for
           compiling to shared objects.

       DDEBUG
           List of debug tags to enable when compiling.

       DDEBUGPREFIX
           DDEBUGPREFIX.

       DDEBUGSUFFIX
           DDEBUGSUFFIX.

       DESCRIPTION
           A long description of the project being packaged. This is included in the relevant
           section of the file that controls the packaging build.

           See the Package builder.

       DESCRIPTION_lang
           A language-specific long description for the specified lang. This is used to populate
           a %description -l section of an RPM .spec file.

           See the Package builder.

       DFILESUFFIX
           DFILESUFFIX.

       DFLAGPREFIX
           DFLAGPREFIX.

       DFLAGS
           General options that are passed to the D compiler.

       DFLAGSUFFIX
           DFLAGSUFFIX.

       DINCPREFIX
           DINCPREFIX.

       DINCSUFFIX
           DLIBFLAGSUFFIX.

       Dir
           A function that converts a string into a Dir instance relative to the target being
           built.

       Dirs
           A function that converts a list of strings into a list of Dir instances relative to
           the target being built.

       DLIB
           Name of the lib tool to use for D codes.

       DLIBCOM
           The command line to use when creating libraries.

       DLIBDIRPREFIX
           DLIBLINKPREFIX.

       DLIBDIRSUFFIX
           DLIBLINKSUFFIX.

       DLIBFLAGPREFIX
           DLIBFLAGPREFIX.

       DLIBFLAGSUFFIX
           DLIBFLAGSUFFIX.

       DLIBLINKPREFIX
           DLIBLINKPREFIX.

       DLIBLINKSUFFIX
           DLIBLINKSUFFIX.

       DLINK
           Name of the linker to use for linking systems including D sources. See also $SHDLINK
           for linking shared objects.

       DLINKCOM
           The command line to use when linking systems including D sources. See also $SHDLINKCOM
           for linking shared objects.

       DLINKFLAGPREFIX
           DLINKFLAGPREFIX.

       DLINKFLAGS
           List of linker flags. See also $SHDLINKFLAGS for linking shared objects.

       DLINKFLAGSUFFIX
           DLINKFLAGSUFFIX.

       DOCBOOK_DEFAULT_XSL_EPUB
           The default XSLT file for the DocbookEpub builder within the current environment, if
           no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_HTML
           The default XSLT file for the DocbookHtml builder within the current environment, if
           no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_HTMLCHUNKED
           The default XSLT file for the DocbookHtmlChunked builder within the current
           environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_HTMLHELP
           The default XSLT file for the DocbookHtmlhelp builder within the current environment,
           if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_MAN
           The default XSLT file for the DocbookMan builder within the current environment, if no
           other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_PDF
           The default XSLT file for the DocbookPdf builder within the current environment, if no
           other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_SLIDESHTML
           The default XSLT file for the DocbookSlidesHtml builder within the current
           environment, if no other XSLT gets specified via keyword.

       DOCBOOK_DEFAULT_XSL_SLIDESPDF
           The default XSLT file for the DocbookSlidesPdf builder within the current environment,
           if no other XSLT gets specified via keyword.

       DOCBOOK_FOP
           The path to the PDF renderer fop or xep, if one of them is installed (fop gets checked
           first).

       DOCBOOK_FOPCOM
           The full command-line for the PDF renderer fop or xep.

       DOCBOOK_FOPCOMSTR
           The string displayed when a renderer like fop or xep is used to create PDF output from
           an XML file.

       DOCBOOK_FOPFLAGS
           Additonal command-line flags for the PDF renderer fop or xep.

       DOCBOOK_XMLLINT
           The path to the external executable xmllint, if it's installed. Note, that this is
           only used as last fallback for resolving XIncludes, if no lxml Python binding can be
           imported in the current system.

       DOCBOOK_XMLLINTCOM
           The full command-line for the external executable xmllint.

       DOCBOOK_XMLLINTCOMSTR
           The string displayed when xmllint is used to resolve XIncludes for a given XML file.

       DOCBOOK_XMLLINTFLAGS
           Additonal command-line flags for the external executable xmllint.

       DOCBOOK_XSLTPROC
           The path to the external executable xsltproc (or saxon, xalan), if one of them is
           installed. Note, that this is only used as last fallback for XSL transformations, if
           no lxml Python binding can be imported in the current system.

       DOCBOOK_XSLTPROCCOM
           The full command-line for the external executable xsltproc (or saxon, xalan).

       DOCBOOK_XSLTPROCCOMSTR
           The string displayed when xsltproc is used to transform an XML file via a given XSLT
           stylesheet.

       DOCBOOK_XSLTPROCFLAGS
           Additonal command-line flags for the external executable xsltproc (or saxon, xalan).

       DOCBOOK_XSLTPROCPARAMS
           Additonal parameters that are not intended for the XSLT processor executable, but the
           XSL processing itself. By default, they get appended at the end of the command line
           for saxon and saxon-xslt, respectively.

       DPATH
           List of paths to search for import modules.

       DRPATHPREFIX
           DRPATHPREFIX.

       DRPATHSUFFIX
           DRPATHSUFFIX.

       DSUFFIXES
           The list of suffixes of files that will be scanned for imported D package files. The
           default list is ['.d'].

       DVERPREFIX
           DVERPREFIX.

       DVERSIONS
           List of version tags to enable when compiling.

       DVERSUFFIX
           DVERSUFFIX.

       DVIPDF
           The TeX DVI file to PDF file converter.

       DVIPDFCOM
           The command line used to convert TeX DVI files into a PDF file.

       DVIPDFCOMSTR
           The string displayed when a TeX DVI file is converted into a PDF file. If this is not
           set, then $DVIPDFCOM (the command line) is displayed.

       DVIPDFFLAGS
           General options passed to the TeX DVI file to PDF file converter.

       DVIPS
           The TeX DVI file to PostScript converter.

       DVIPSFLAGS
           General options passed to the TeX DVI file to PostScript converter.

       ENV
           The execution environment - a dictionary of environment variables used when SCons
           invokes external commands to build targets defined in this construction environment.
           When $ENV is passed to a command, all list values are assumed to be path lists and are
           joined using the search path separator. Any other non-string values are coerced to a
           string.

           Note that by default SCons does not propagate the environment in effect when you
           execute scons (the "shell environment") to the execution environment. This is so that
           builds will be guaranteed repeatable regardless of the environment variables set at
           the time scons is invoked. If you want to propagate a shell environment variable to
           the commands executed to build target files, you must do so explicitly. A common
           example is the system PATH environment variable, so that scons will find utilities the
           same way as the invoking shell (or other process):

               import os
               env = Environment(ENV={'PATH': os.environ['PATH']})

           Although it is usually not recommended, you can propagate the entire shell environment
           in one go:

               import os
               env = Environment(ENV=os.environ.copy())

       ESCAPE
           A function that will be called to escape shell special characters in command lines.
           The function should take one argument: the command line string to escape; and should
           return the escaped command line.

       F03
           The Fortran 03 compiler. You should normally set the $FORTRAN variable, which
           specifies the default Fortran compiler for all Fortran versions. You only need to set
           $F03 if you need to use a specific compiler or compiler version for Fortran 03 files.

       F03COM
           The command line used to compile a Fortran 03 source file to an object file. You only
           need to set $F03COM if you need to use a specific command line for Fortran 03 files.
           You should normally set the $FORTRANCOM variable, which specifies the default command
           line for all Fortran versions.

       F03COMSTR
           If set, the string displayed when a Fortran 03 source file is compiled to an object
           file. If not set, then $F03COM or $FORTRANCOM (the command line) is displayed.

       F03FILESUFFIXES
           The list of file extensions for which the F03 dialect will be used. By default, this
           is ['.f03']

       F03FLAGS
           General user-specified options that are passed to the Fortran 03 compiler. Note that
           this variable does not contain -I (or similar) include search path options that scons
           generates automatically from $F03PATH. See $_F03INCFLAGS below, for the variable that
           expands to those options. You only need to set $F03FLAGS if you need to define
           specific user options for Fortran 03 files. You should normally set the $FORTRANFLAGS
           variable, which specifies the user-specified options passed to the default Fortran
           compiler for all Fortran versions.

       _F03INCFLAGS
           An automatically-generated construction variable containing the Fortran 03 compiler
           command-line options for specifying directories to be searched for include files. The
           value of $_F03INCFLAGS is created by appending $INCPREFIX and $INCSUFFIX to the
           beginning and end of each directory in $F03PATH.

       F03PATH
           The list of directories that the Fortran 03 compiler will search for include
           directories. The implicit dependency scanner will search these directories for include
           files. Don't explicitly put include directory arguments in $F03FLAGS because the
           result will be non-portable and the directories will not be searched by the dependency
           scanner. Note: directory names in $F03PATH will be looked-up relative to the
           SConscript directory when they are used in a command. To force scons to look-up a
           directory relative to the root of the source tree use #: You only need to set $F03PATH
           if you need to define a specific include path for Fortran 03 files. You should
           normally set the $FORTRANPATH variable, which specifies the include path for the
           default Fortran compiler for all Fortran versions.

               env = Environment(F03PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F03PATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_F03INCFLAGS construction variable, which is constructed by appending the values of
           the $INCPREFIX and $INCSUFFIX construction variables to the beginning and end of each
           directory in $F03PATH. Any command lines you define that need the F03PATH directory
           list should include $_F03INCFLAGS:

               env = Environment(F03COM="my_compiler $_F03INCFLAGS -c -o $TARGET $SOURCE")

       F03PPCOM
           The command line used to compile a Fortran 03 source file to an object file after
           first running the file through the C preprocessor. Any options specified in the
           $F03FLAGS and $CPPFLAGS construction variables are included on this command line. You
           only need to set $F03PPCOM if you need to use a specific C-preprocessor command line
           for Fortran 03 files. You should normally set the $FORTRANPPCOM variable, which
           specifies the default C-preprocessor command line for all Fortran versions.

       F03PPCOMSTR
           If set, the string displayed when a Fortran 03 source file is compiled to an object
           file after first running the file through the C preprocessor. If not set, then
           $F03PPCOM or $FORTRANPPCOM (the command line) is displayed.

       F03PPFILESUFFIXES
           The list of file extensions for which the compilation + preprocessor pass for F03
           dialect will be used. By default, this is empty.

       F08
           The Fortran 08 compiler. You should normally set the $FORTRAN variable, which
           specifies the default Fortran compiler for all Fortran versions. You only need to set
           $F08 if you need to use a specific compiler or compiler version for Fortran 08 files.

       F08COM
           The command line used to compile a Fortran 08 source file to an object file. You only
           need to set $F08COM if you need to use a specific command line for Fortran 08 files.
           You should normally set the $FORTRANCOM variable, which specifies the default command
           line for all Fortran versions.

       F08COMSTR
           If set, the string displayed when a Fortran 08 source file is compiled to an object
           file. If not set, then $F08COM or $FORTRANCOM (the command line) is displayed.

       F08FILESUFFIXES
           The list of file extensions for which the F08 dialect will be used. By default, this
           is ['.f08']

       F08FLAGS
           General user-specified options that are passed to the Fortran 08 compiler. Note that
           this variable does not contain -I (or similar) include search path options that scons
           generates automatically from $F08PATH. See $_F08INCFLAGS below, for the variable that
           expands to those options. You only need to set $F08FLAGS if you need to define
           specific user options for Fortran 08 files. You should normally set the $FORTRANFLAGS
           variable, which specifies the user-specified options passed to the default Fortran
           compiler for all Fortran versions.

       _F08INCFLAGS
           An automatically-generated construction variable containing the Fortran 08 compiler
           command-line options for specifying directories to be searched for include files. The
           value of $_F08INCFLAGS is created by appending $INCPREFIX and $INCSUFFIX to the
           beginning and end of each directory in $F08PATH.

       F08PATH
           The list of directories that the Fortran 08 compiler will search for include
           directories. The implicit dependency scanner will search these directories for include
           files. Don't explicitly put include directory arguments in $F08FLAGS because the
           result will be non-portable and the directories will not be searched by the dependency
           scanner. Note: directory names in $F08PATH will be looked-up relative to the
           SConscript directory when they are used in a command. To force scons to look-up a
           directory relative to the root of the source tree use #: You only need to set $F08PATH
           if you need to define a specific include path for Fortran 08 files. You should
           normally set the $FORTRANPATH variable, which specifies the include path for the
           default Fortran compiler for all Fortran versions.

               env = Environment(F08PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F08PATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_F08INCFLAGS construction variable, which is constructed by appending the values of
           the $INCPREFIX and $INCSUFFIX construction variables to the beginning and end of each
           directory in $F08PATH. Any command lines you define that need the F08PATH directory
           list should include $_F08INCFLAGS:

               env = Environment(F08COM="my_compiler $_F08INCFLAGS -c -o $TARGET $SOURCE")

       F08PPCOM
           The command line used to compile a Fortran 08 source file to an object file after
           first running the file through the C preprocessor. Any options specified in the
           $F08FLAGS and $CPPFLAGS construction variables are included on this command line. You
           only need to set $F08PPCOM if you need to use a specific C-preprocessor command line
           for Fortran 08 files. You should normally set the $FORTRANPPCOM variable, which
           specifies the default C-preprocessor command line for all Fortran versions.

       F08PPCOMSTR
           If set, the string displayed when a Fortran 08 source file is compiled to an object
           file after first running the file through the C preprocessor. If not set, then
           $F08PPCOM or $FORTRANPPCOM (the command line) is displayed.

       F08PPFILESUFFIXES
           The list of file extensions for which the compilation + preprocessor pass for F08
           dialect will be used. By default, this is empty.

       F77
           The Fortran 77 compiler. You should normally set the $FORTRAN variable, which
           specifies the default Fortran compiler for all Fortran versions. You only need to set
           $F77 if you need to use a specific compiler or compiler version for Fortran 77 files.

       F77COM
           The command line used to compile a Fortran 77 source file to an object file. You only
           need to set $F77COM if you need to use a specific command line for Fortran 77 files.
           You should normally set the $FORTRANCOM variable, which specifies the default command
           line for all Fortran versions.

       F77COMSTR
           If set, the string displayed when a Fortran 77 source file is compiled to an object
           file. If not set, then $F77COM or $FORTRANCOM (the command line) is displayed.

       F77FILESUFFIXES
           The list of file extensions for which the F77 dialect will be used. By default, this
           is ['.f77']

       F77FLAGS
           General user-specified options that are passed to the Fortran 77 compiler. Note that
           this variable does not contain -I (or similar) include search path options that scons
           generates automatically from $F77PATH. See $_F77INCFLAGS below, for the variable that
           expands to those options. You only need to set $F77FLAGS if you need to define
           specific user options for Fortran 77 files. You should normally set the $FORTRANFLAGS
           variable, which specifies the user-specified options passed to the default Fortran
           compiler for all Fortran versions.

       _F77INCFLAGS
           An automatically-generated construction variable containing the Fortran 77 compiler
           command-line options for specifying directories to be searched for include files. The
           value of $_F77INCFLAGS is created by appending $INCPREFIX and $INCSUFFIX to the
           beginning and end of each directory in $F77PATH.

       F77PATH
           The list of directories that the Fortran 77 compiler will search for include
           directories. The implicit dependency scanner will search these directories for include
           files. Don't explicitly put include directory arguments in $F77FLAGS because the
           result will be non-portable and the directories will not be searched by the dependency
           scanner. Note: directory names in $F77PATH will be looked-up relative to the
           SConscript directory when they are used in a command. To force scons to look-up a
           directory relative to the root of the source tree use #: You only need to set $F77PATH
           if you need to define a specific include path for Fortran 77 files. You should
           normally set the $FORTRANPATH variable, which specifies the include path for the
           default Fortran compiler for all Fortran versions.

               env = Environment(F77PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F77PATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_F77INCFLAGS construction variable, which is constructed by appending the values of
           the $INCPREFIX and $INCSUFFIX construction variables to the beginning and end of each
           directory in $F77PATH. Any command lines you define that need the F77PATH directory
           list should include $_F77INCFLAGS:

               env = Environment(F77COM="my_compiler $_F77INCFLAGS -c -o $TARGET $SOURCE")

       F77PPCOM
           The command line used to compile a Fortran 77 source file to an object file after
           first running the file through the C preprocessor. Any options specified in the
           $F77FLAGS and $CPPFLAGS construction variables are included on this command line. You
           only need to set $F77PPCOM if you need to use a specific C-preprocessor command line
           for Fortran 77 files. You should normally set the $FORTRANPPCOM variable, which
           specifies the default C-preprocessor command line for all Fortran versions.

       F77PPCOMSTR
           If set, the string displayed when a Fortran 77 source file is compiled to an object
           file after first running the file through the C preprocessor. If not set, then
           $F77PPCOM or $FORTRANPPCOM (the command line) is displayed.

       F77PPFILESUFFIXES
           The list of file extensions for which the compilation + preprocessor pass for F77
           dialect will be used. By default, this is empty.

       F90
           The Fortran 90 compiler. You should normally set the $FORTRAN variable, which
           specifies the default Fortran compiler for all Fortran versions. You only need to set
           $F90 if you need to use a specific compiler or compiler version for Fortran 90 files.

       F90COM
           The command line used to compile a Fortran 90 source file to an object file. You only
           need to set $F90COM if you need to use a specific command line for Fortran 90 files.
           You should normally set the $FORTRANCOM variable, which specifies the default command
           line for all Fortran versions.

       F90COMSTR
           If set, the string displayed when a Fortran 90 source file is compiled to an object
           file. If not set, then $F90COM or $FORTRANCOM (the command line) is displayed.

       F90FILESUFFIXES
           The list of file extensions for which the F90 dialect will be used. By default, this
           is ['.f90']

       F90FLAGS
           General user-specified options that are passed to the Fortran 90 compiler. Note that
           this variable does not contain -I (or similar) include search path options that scons
           generates automatically from $F90PATH. See $_F90INCFLAGS below, for the variable that
           expands to those options. You only need to set $F90FLAGS if you need to define
           specific user options for Fortran 90 files. You should normally set the $FORTRANFLAGS
           variable, which specifies the user-specified options passed to the default Fortran
           compiler for all Fortran versions.

       _F90INCFLAGS
           An automatically-generated construction variable containing the Fortran 90 compiler
           command-line options for specifying directories to be searched for include files. The
           value of $_F90INCFLAGS is created by appending $INCPREFIX and $INCSUFFIX to the
           beginning and end of each directory in $F90PATH.

       F90PATH
           The list of directories that the Fortran 90 compiler will search for include
           directories. The implicit dependency scanner will search these directories for include
           files. Don't explicitly put include directory arguments in $F90FLAGS because the
           result will be non-portable and the directories will not be searched by the dependency
           scanner. Note: directory names in $F90PATH will be looked-up relative to the
           SConscript directory when they are used in a command. To force scons to look-up a
           directory relative to the root of the source tree use #: You only need to set $F90PATH
           if you need to define a specific include path for Fortran 90 files. You should
           normally set the $FORTRANPATH variable, which specifies the include path for the
           default Fortran compiler for all Fortran versions.

               env = Environment(F90PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F90PATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_F90INCFLAGS construction variable, which is constructed by appending the values of
           the $INCPREFIX and $INCSUFFIX construction variables to the beginning and end of each
           directory in $F90PATH. Any command lines you define that need the F90PATH directory
           list should include $_F90INCFLAGS:

               env = Environment(F90COM="my_compiler $_F90INCFLAGS -c -o $TARGET $SOURCE")

       F90PPCOM
           The command line used to compile a Fortran 90 source file to an object file after
           first running the file through the C preprocessor. Any options specified in the
           $F90FLAGS and $CPPFLAGS construction variables are included on this command line. You
           only need to set $F90PPCOM if you need to use a specific C-preprocessor command line
           for Fortran 90 files. You should normally set the $FORTRANPPCOM variable, which
           specifies the default C-preprocessor command line for all Fortran versions.

       F90PPCOMSTR
           If set, the string displayed when a Fortran 90 source file is compiled after first
           running the file through the C preprocessor. If not set, then $F90PPCOM or
           $FORTRANPPCOM (the command line) is displayed.

       F90PPFILESUFFIXES
           The list of file extensions for which the compilation + preprocessor pass for F90
           dialect will be used. By default, this is empty.

       F95
           The Fortran 95 compiler. You should normally set the $FORTRAN variable, which
           specifies the default Fortran compiler for all Fortran versions. You only need to set
           $F95 if you need to use a specific compiler or compiler version for Fortran 95 files.

       F95COM
           The command line used to compile a Fortran 95 source file to an object file. You only
           need to set $F95COM if you need to use a specific command line for Fortran 95 files.
           You should normally set the $FORTRANCOM variable, which specifies the default command
           line for all Fortran versions.

       F95COMSTR
           If set, the string displayed when a Fortran 95 source file is compiled to an object
           file. If not set, then $F95COM or $FORTRANCOM (the command line) is displayed.

       F95FILESUFFIXES
           The list of file extensions for which the F95 dialect will be used. By default, this
           is ['.f95']

       F95FLAGS
           General user-specified options that are passed to the Fortran 95 compiler. Note that
           this variable does not contain -I (or similar) include search path options that scons
           generates automatically from $F95PATH. See $_F95INCFLAGS below, for the variable that
           expands to those options. You only need to set $F95FLAGS if you need to define
           specific user options for Fortran 95 files. You should normally set the $FORTRANFLAGS
           variable, which specifies the user-specified options passed to the default Fortran
           compiler for all Fortran versions.

       _F95INCFLAGS
           An automatically-generated construction variable containing the Fortran 95 compiler
           command-line options for specifying directories to be searched for include files. The
           value of $_F95INCFLAGS is created by appending $INCPREFIX and $INCSUFFIX to the
           beginning and end of each directory in $F95PATH.

       F95PATH
           The list of directories that the Fortran 95 compiler will search for include
           directories. The implicit dependency scanner will search these directories for include
           files. Don't explicitly put include directory arguments in $F95FLAGS because the
           result will be non-portable and the directories will not be searched by the dependency
           scanner. Note: directory names in $F95PATH will be looked-up relative to the
           SConscript directory when they are used in a command. To force scons to look-up a
           directory relative to the root of the source tree use #: You only need to set $F95PATH
           if you need to define a specific include path for Fortran 95 files. You should
           normally set the $FORTRANPATH variable, which specifies the include path for the
           default Fortran compiler for all Fortran versions.

               env = Environment(F95PATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(F95PATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_F95INCFLAGS construction variable, which is constructed by appending the values of
           the $INCPREFIX and $INCSUFFIX construction variables to the beginning and end of each
           directory in $F95PATH. Any command lines you define that need the F95PATH directory
           list should include $_F95INCFLAGS:

               env = Environment(F95COM="my_compiler $_F95INCFLAGS -c -o $TARGET $SOURCE")

       F95PPCOM
           The command line used to compile a Fortran 95 source file to an object file after
           first running the file through the C preprocessor. Any options specified in the
           $F95FLAGS and $CPPFLAGS construction variables are included on this command line. You
           only need to set $F95PPCOM if you need to use a specific C-preprocessor command line
           for Fortran 95 files. You should normally set the $FORTRANPPCOM variable, which
           specifies the default C-preprocessor command line for all Fortran versions.

       F95PPCOMSTR
           If set, the string displayed when a Fortran 95 source file is compiled to an object
           file after first running the file through the C preprocessor. If not set, then
           $F95PPCOM or $FORTRANPPCOM (the command line) is displayed.

       F95PPFILESUFFIXES
           The list of file extensions for which the compilation + preprocessor pass for F95
           dialect will be used. By default, this is empty.

       File
           A function that converts a string into a File instance relative to the target being
           built.

       FILE_ENCODING
           File encoding used for files written by Textfile and Substfile. Set to "utf-8" by
           default.  Added in version 4.5.0.

       FORTRAN
           The default Fortran compiler for all versions of Fortran.

       FORTRANCOM
           The command line used to compile a Fortran source file to an object file. By default,
           any options specified in the $FORTRANFLAGS, $_FORTRANMODFLAG, and $_FORTRANINCFLAGS
           construction variables are included on this command line.

       FORTRANCOMMONFLAGS
           General user-specified options that are passed to the Fortran compiler. Similar to
           $FORTRANFLAGS, but this construction variable is applied to all dialects.

           New in version 4.4.

       FORTRANCOMSTR
           If set, the string displayed when a Fortran source file is compiled to an object file.
           If not set, then $FORTRANCOM (the command line) is displayed.

       FORTRANFILESUFFIXES
           The list of file extensions for which the FORTRAN dialect will be used. By default,
           this is ['.f', '.for', '.ftn']

       FORTRANFLAGS
           General user-specified options for the FORTRAN dialect that are passed to the Fortran
           compiler. Note that this variable does not contain -I (or similar) include or module
           search path options that scons generates automatically from $FORTRANPATH. See
           $_FORTRANINCFLAGS and $_FORTRANMODFLAG for the construction variables that expand
           those options.

       _FORTRANINCFLAGS
           An automatically-generated construction variable containing the Fortran compiler
           command-line options for specifying directories to be searched for include files and
           module files. The value of $_FORTRANINCFLAGS is created by respectively prepending and
           appending $INCPREFIX and $INCSUFFIX to the beginning and end of each directory in
           $FORTRANPATH.

       FORTRANMODDIR
           Directory location where the Fortran compiler should place any module files it
           generates. This variable is empty, by default. Some Fortran compilers will internally
           append this directory in the search path for module files, as well.

       FORTRANMODDIRPREFIX
           The prefix used to specify a module directory on the Fortran compiler command line.
           This will be prepended to the beginning of the directory in the $FORTRANMODDIR
           construction variables when the $_FORTRANMODFLAG variables is automatically generated.

       FORTRANMODDIRSUFFIX
           The suffix used to specify a module directory on the Fortran compiler command line.
           This will be appended to the end of the directory in the $FORTRANMODDIR construction
           variables when the $_FORTRANMODFLAG variables is automatically generated.

       _FORTRANMODFLAG
           An automatically-generated construction variable containing the Fortran compiler
           command-line option for specifying the directory location where the Fortran compiler
           should place any module files that happen to get generated during compilation. The
           value of $_FORTRANMODFLAG is created by respectively prepending and appending
           $FORTRANMODDIRPREFIX and $FORTRANMODDIRSUFFIX to the beginning and end of the
           directory in $FORTRANMODDIR.

       FORTRANMODPREFIX
           The module file prefix used by the Fortran compiler. SCons assumes that the Fortran
           compiler follows the quasi-standard naming convention for module files of
           module_name.mod. As a result, this variable is left empty, by default. For situations
           in which the compiler does not necessarily follow the normal convention, the user may
           use this variable. Its value will be appended to every module file name as scons
           attempts to resolve dependencies.

       FORTRANMODSUFFIX
           The module file suffix used by the Fortran compiler. SCons assumes that the Fortran
           compiler follows the quasi-standard naming convention for module files of
           module_name.mod. As a result, this variable is set to ".mod", by default. For
           situations in which the compiler does not necessarily follow the normal convention,
           the user may use this variable. Its value will be appended to every module file name
           as scons attempts to resolve dependencies.

       FORTRANPATH
           The list of directories that the Fortran compiler will search for include files and
           (for some compilers) module files. The Fortran implicit dependency scanner will search
           these directories for include files (but not module files since they are autogenerated
           and, as such, may not actually exist at the time the scan takes place). Don't
           explicitly put include directory arguments in FORTRANFLAGS because the result will be
           non-portable and the directories will not be searched by the dependency scanner. Note:
           directory names in FORTRANPATH will be looked-up relative to the SConscript directory
           when they are used in a command. To force scons to look-up a directory relative to the
           root of the source tree use #:

               env = Environment(FORTRANPATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(FORTRANPATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_FORTRANINCFLAGS construction variable, which is constructed by respectively
           prepending and appending the values of the $INCPREFIX and $INCSUFFIX construction
           variables to the beginning and end of each directory in $FORTRANPATH. Any command
           lines you define that need the FORTRANPATH directory list should include
           $_FORTRANINCFLAGS:

               env = Environment(FORTRANCOM="my_compiler $_FORTRANINCFLAGS -c -o $TARGET $SOURCE")

       FORTRANPPCOM
           The command line used to compile a Fortran source file to an object file after first
           running the file through the C preprocessor. By default, any options specified in the
           $FORTRANFLAGS, $CPPFLAGS, $_CPPDEFFLAGS, $_FORTRANMODFLAG, and $_FORTRANINCFLAGS
           construction variables are included on this command line.

       FORTRANPPCOMSTR
           If set, the string displayed when a Fortran source file is compiled to an object file
           after first running the file through the C preprocessor. If not set, then
           $FORTRANPPCOM (the command line) is displayed.

       FORTRANPPFILESUFFIXES
           The list of file extensions for which the compilation + preprocessor pass for FORTRAN
           dialect will be used. By default, this is ['.fpp', '.FPP']

       FORTRANSUFFIXES
           The list of suffixes of files that will be scanned for Fortran implicit dependencies
           (INCLUDE lines and USE statements). The default list is:

               [".f", ".F", ".for", ".FOR", ".ftn", ".FTN", ".fpp", ".FPP",
               ".f77", ".F77", ".f90", ".F90", ".f95", ".F95"]

       FRAMEWORKPATH
           On Mac OS X with gcc, a list containing the paths to search for frameworks. Used by
           the compiler to find framework-style includes like #include <Fmwk/Header.h>. Used by
           the linker to find user-specified frameworks when linking (see $FRAMEWORKS). For
           example:

               env.AppendUnique(FRAMEWORKPATH='#myframeworkdir')

           will add

               ... -Fmyframeworkdir

           to the compiler and linker command lines.

       _FRAMEWORKPATH
           On Mac OS X with gcc, an automatically-generated construction variable containing the
           linker command-line options corresponding to $FRAMEWORKPATH.

       FRAMEWORKPATHPREFIX
           On Mac OS X with gcc, the prefix to be used for the FRAMEWORKPATH entries. (see
           $FRAMEWORKPATH). The default value is -F.

       FRAMEWORKPREFIX
           On Mac OS X with gcc, the prefix to be used for linking in frameworks (see
           $FRAMEWORKS). The default value is -framework.

       FRAMEWORKS
           On Mac OS X with gcc, a list of the framework names to be linked into a program or
           shared library or bundle. The default value is the empty list. For example:

               env.AppendUnique(FRAMEWORKS=Split('System Cocoa SystemConfiguration'))

       _FRAMEWORKS
           On Mac OS X with gcc, an automatically-generated construction variable containing the
           linker command-line options for linking with FRAMEWORKS.

       FRAMEWORKSFLAGS
           On Mac OS X with gcc, general user-supplied frameworks options to be added at the end
           of a command line building a loadable module. (This has been largely superseded by the
           $FRAMEWORKPATH, $FRAMEWORKPATHPREFIX, $FRAMEWORKPREFIX and $FRAMEWORKS variables
           described above.)

       GS
           The Ghostscript program used to, for example, convert PostScript to PDF files.

       GSCOM
           The full Ghostscript command line used for the conversion process. Its default value
           is “$GS $GSFLAGS -sOutputFile=$TARGET $SOURCES”.

       GSCOMSTR
           The string displayed when Ghostscript is called for the conversion process. If this is
           not set (the default), then $GSCOM (the command line) is displayed.

       GSFLAGS
           General options passed to the Ghostscript program, when converting PostScript to PDF
           files for example. Its default value is “-dNOPAUSE -dBATCH -sDEVICE=pdfwrite”

       HOST_ARCH
           The name of the host hardware architecture used to create this construction
           environment. The platform code sets this when initializing (see $PLATFORM and the
           platform argument to Environment). Note the detected name of the architecture may not
           be identical to that returned by the Python platform.machine method.

           On the win32 platform, if the Microsoft Visual C++ compiler is available, msvc tool
           setup is done using $HOST_ARCH and $TARGET_ARCH. Changing the values at any later time
           will not cause the tool to be reinitialized. Valid host arch values are x86 and arm
           for 32-bit hosts and amd64 and x86_64 for 64-bit hosts.

           Should be considered immutable.  $HOST_ARCH is not currently used by other platforms,
           but the option is reserved to do so in future

       HOST_OS
           The name of the host operating system for the platform used to create this
           construction environment. The platform code sets this when initializing (see $PLATFORM
           and the platform argument to Environment).

           Should be considered immutable.  $HOST_OS is not currently used by SCons, but the
           option is reserved to do so in future

       IDLSUFFIXES
           The list of suffixes of files that will be scanned for IDL implicit dependencies
           (#include or import lines). The default list is:

               [".idl", ".IDL"]

       IMPLIBNOVERSIONSYMLINKS
           Used to override $SHLIBNOVERSIONSYMLINKS/$LDMODULENOVERSIONSYMLINKS when creating
           versioned import library for a shared library/loadable module. If not defined, then
           $SHLIBNOVERSIONSYMLINKS/$LDMODULENOVERSIONSYMLINKS is used to determine whether to
           disable symlink generation or not.

       IMPLIBPREFIX
           The prefix used for import library names. For example, cygwin uses import libraries
           (libfoo.dll.a) in pair with dynamic libraries (cygfoo.dll). The cyglink linker sets
           $IMPLIBPREFIX to 'lib' and $SHLIBPREFIX to 'cyg'.

       IMPLIBSUFFIX
           The suffix used for import library names. For example, cygwin uses import libraries
           (libfoo.dll.a) in pair with dynamic libraries (cygfoo.dll). The cyglink linker sets
           $IMPLIBSUFFIX to '.dll.a' and $SHLIBSUFFIX to '.dll'.

       IMPLIBVERSION
           Used to override $SHLIBVERSION/$LDMODULEVERSION when generating versioned import
           library for a shared library/loadable module. If undefined, the
           $SHLIBVERSION/$LDMODULEVERSION is used to determine the version of versioned import
           library.

       IMPLICIT_COMMAND_DEPENDENCIES
           Controls whether or not SCons will add implicit dependencies for the commands executed
           to build targets.

           By default, SCons will add to each target an implicit dependency on the command
           represented by the first argument of any command line it executes (which is typically
           the command itself). By setting such a dependency, SCons can determine that a target
           should be rebuilt if the command changes, such as when a compiler is upgraded to a new
           version. The specific file for the dependency is found by searching the PATH variable
           in the ENV dictionary in the construction environment used to execute the command. The
           default is the same as setting the construction variable
           $IMPLICIT_COMMAND_DEPENDENCIES to a True-like value (“true”, “yes”, or “1” - but not a
           number greater than one, as that has a different meaning).

           Action strings can be segmented by the use of an AND operator, &&. In a segemented
           string, each segment is a separate “command line”, these are run sequentially until
           one fails or the entire sequence has been executed. If an action string is segmented,
           then the selected behavior of $IMPLICIT_COMMAND_DEPENDENCIES is applied to each
           segment.

           If $IMPLICIT_COMMAND_DEPENDENCIES is set to a False-like value (“none”, “false”, “no”,
           “0”, etc.), then the implicit dependency will not be added to the targets built with
           that construction environment.

           If $IMPLICIT_COMMAND_DEPENDENCIES is set to “2” or higher, then that number of
           arguments in the command line will be scanned for relative or absolute paths. If any
           are present, they will be added as implicit dependencies to the targets built with
           that construction environment. The first argument in the command line will be searched
           for using the PATH variable in the ENV dictionary in the construction environment used
           to execute the command. The other arguments will only be found if they are absolute
           paths or valid paths relative to the working directory.

           If $IMPLICIT_COMMAND_DEPENDENCIES is set to “all”, then all arguments in the command
           line will be scanned for relative or absolute paths. If any are present, they will be
           added as implicit dependencies to the targets built with that construction
           environment. The first argument in the command line will be searched for using the
           PATH variable in the ENV dictionary in the construction environment used to execute
           the command. The other arguments will only be found if they are absolute paths or
           valid paths relative to the working directory.

               env = Environment(IMPLICIT_COMMAND_DEPENDENCIES=False)

       INCPREFIX
           The prefix used to specify an include directory on the C compiler command line. This
           will be prepended to each directory in the $CPPPATH and $FORTRANPATH construction
           variables when the $_CPPINCFLAGS and $_FORTRANINCFLAGS variables are automatically
           generated.

       INCSUFFIX
           The suffix used to specify an include directory on the C compiler command line. This
           will be appended to each directory in the $CPPPATH and $FORTRANPATH construction
           variables when the $_CPPINCFLAGS and $_FORTRANINCFLAGS variables are automatically
           generated.

       INSTALL
           A function to be called to install a file into a destination file name. The default
           function copies the file into the destination (and sets the destination file's mode
           and permission bits to match the source file's). The function takes the following
           arguments:

               def install(dest, source, env):

           dest is the path name of the destination file.  source is the path name of the source
           file.  env is the construction environment (a dictionary of construction values) in
           force for this file installation.

       INSTALLSTR
           The string displayed when a file is installed into a destination file name. The
           default is:

               Install file: "$SOURCE" as "$TARGET"

       INTEL_C_COMPILER_VERSION
           Set by the intelc Tool to the major version number of the Intel C compiler selected
           for use.

       JAR
           The Java archive tool.

       JARCHDIR
           The directory to which the Java archive tool should change (using the -C option).

       JARCOM
           The command line used to call the Java archive tool.

       JARCOMSTR
           The string displayed when the Java archive tool is called If this is not set, then
           $JARCOM (the command line) is displayed.

               env = Environment(JARCOMSTR="JARchiving $SOURCES into $TARGET")

       JARFLAGS
           General options passed to the Java archive tool. By default this is set to cf to
           create the necessary jar file.

       JARSUFFIX
           The suffix for Java archives: .jar by default.

       JAVABOOTCLASSPATH
           Specifies the location of the bootstrap class files. Can be specified as a string or
           Node object, or as a list of strings or Node objects.

           The value will be added to the JDK command lines via the -bootclasspath option, which
           requires a system-specific search path separator. This will be supplied by SCons as
           needed when it constructs the command line if $JAVABOOTCLASSPATH is provided in list
           form. If $JAVABOOTCLASSPATH is a single string containing search path separator
           characters (: for POSIX systems or ; for Windows), it will not be modified; and so is
           inherently system-specific; to supply the path in a system-independent manner, give
           $JAVABOOTCLASSPATH as a list of paths instead.

               Note
               Can only be used when compiling for releases prior to JDK 9.

       JAVAC
           The Java compiler.

       JAVACCOM
           The command line used to compile a directory tree containing Java source files to
           corresponding Java class files. Any options specified in the $JAVACFLAGS construction
           variable are included on this command line.

       JAVACCOMSTR
           The string displayed when compiling a directory tree of Java source files to
           corresponding Java class files. If this is not set, then $JAVACCOM (the command line)
           is displayed.

               env = Environment(JAVACCOMSTR="Compiling class files $TARGETS from $SOURCES")

       JAVACFLAGS
           General options that are passed to the Java compiler.

       JAVACLASSDIR
           The directory in which Java class files may be found. This is stripped from the
           beginning of any Java .class file names supplied to the JavaH builder.

       JAVACLASSPATH
           Specifies the class search path for the JDK tools. Can be specified as a string or
           Node object, or as a list of strings or Node objects. Class path entries may be
           directory names to search for class files or packages, pathnames to archives (.jar or
           .zip) containing classes, or paths ending in a "base name wildcard" character (*),
           which matches files in that directory with a .jar suffix. See the Java documentation
           for more details.

           The value will be added to the JDK command lines via the -classpath option, which
           requires a system-specific search path separator. This will be supplied by SCons as
           needed when it constructs the command line if $JAVACLASSPATH is provided in list form.
           If $JAVACLASSPATH is a single string containing search path separator characters (:
           for POSIX systems or ; for Windows), it will be split on the separator into a list of
           individual paths for dependency scanning purposes. It will not be modified for JDK
           command-line usage, so such a string is inherently system-specific; to supply the path
           in a system-independent manner, give $JAVACLASSPATH as a list of paths instead.

               Note
               SCons always supplies a -sourcepath when invoking the Java compiler javac,
               regardless of the setting of $JAVASOURCEPATH, as it passes the path(s) to the
               source(s) supplied in the call to the Java builder via -sourcepath . From the
               documentation of the standard Java toolkit for javac: “If not compiling code for
               modules, if the --source-path or -sourcepath option is not specified, then the
               user class path is also searched for source files.”  Since -sourcepath is always
               supplied, javac will not use the contents of the value of $JAVACLASSPATH when
               searching for sources.

       JAVACLASSSUFFIX
           The suffix for Java class files; .class by default.

       JAVAH
           The Java generator for C header and stub files.

       JAVAHCOM
           The command line used to generate C header and stub files from Java classes. Any
           options specified in the $JAVAHFLAGS construction variable are included on this
           command line.

       JAVAHCOMSTR
           The string displayed when C header and stub files are generated from Java classes. If
           this is not set, then $JAVAHCOM (the command line) is displayed.

               env = Environment(JAVAHCOMSTR="Generating header/stub file(s) $TARGETS from $SOURCES")

       JAVAHFLAGS
           General options passed to the C header and stub file generator for Java classes.

       JAVAINCLUDES
           Include path for Java header files (such as jni.h).

       JAVAPROCESSORPATH
           Specifies the location of the annotation processor class files. Can be specified as a
           string or Node object, or as a list of strings or Node objects.

           The value will be added to the JDK command lines via the -processorpath option, which
           requires a system-specific search path separator. This will be supplied by SCons as
           needed when it constructs the command line if $JAVAPROCESSORPATH is provided in list
           form. If $JAVAPROCESSORPATH is a single string containing search path separator
           characters (: for POSIX systems or ; for Windows), it will not be modified; and so is
           inherently system-specific; to supply the path in a system-independent manner, give
           $JAVAPROCESSORPATH as a list of paths instead.

           New in version 4.5.0

       JAVASOURCEPATH
           Specifies the list of directories that will be searched for input (source) .java
           files. Can be specified as a string or Node object, or as a list of strings or Node
           objects.

           The value will be added to the JDK command lines via the -sourcepath option, which
           requires a system-specific search path separator, This will be supplied by SCons as
           needed when it constructs the command line if $JAVASOURCEPATH is provided in list
           form. If $JAVASOURCEPATH is a single string containing search path separator
           characters (: for POSIX systems or ; for Windows), it will not be modified, and so is
           inherently system-specific; to supply the path in a system-independent manner, give
           $JAVASOURCEPATH as a list of paths instead.

           Note that the specified directories are only added to the command line via the
           -sourcepath option.  SCons does not currently search the $JAVASOURCEPATH directories
           for dependent .java files.

       JAVASUFFIX
           The suffix for Java files; .java by default.

       JAVAVERSION
           Specifies the Java version being used by the Java builder. Set this to specify the
           version of Java targeted by the javac compiler. This is sometimes necessary because
           Java 1.5 changed the file names that are created for nested anonymous inner classes,
           which can cause a mismatch with the files that SCons expects will be generated by the
           javac compiler. Setting $JAVAVERSION to a version greater than 1.4 makes SCons realize
           that a build with such a compiler is actually up to date. The default is 1.4.

           While this is not primarily intended for selecting one version of the Java compiler
           vs. another, it does have that effect on the Windows platform. A more precise approach
           is to set $JAVAC (and related construction variables for related utilities) to the
           path to the specific Java compiler you want, if that is not the default compiler. On
           non-Windows platforms, the alternatives system may provide a way to adjust the default
           Java compiler without having to specify explicit paths.

       LATEX
           The LaTeX structured formatter and typesetter.

       LATEXCOM
           The command line used to call the LaTeX structured formatter and typesetter.

       LATEXCOMSTR
           The string displayed when calling the LaTeX structured formatter and typesetter. If
           this is not set, then $LATEXCOM (the command line) is displayed.

               env = Environment(LATEXCOMSTR = "Building $TARGET from LaTeX input $SOURCES")

       LATEXFLAGS
           General options passed to the LaTeX structured formatter and typesetter.

       LATEXRETRIES
           The maximum number of times that LaTeX will be re-run if the .log generated by the
           $LATEXCOM command indicates that there are undefined references. The default is to try
           to resolve undefined references by re-running LaTeX up to three times.

       LATEXSUFFIXES
           The list of suffixes of files that will be scanned for LaTeX implicit dependencies
           (\include or \import files). The default list is:

               [".tex", ".ltx", ".latex"]

       LDMODULE
           The linker for building loadable modules. By default, this is the same as $SHLINK.

       LDMODULECOM
           The command line for building loadable modules. On Mac OS X, this uses the $LDMODULE,
           $LDMODULEFLAGS and $FRAMEWORKSFLAGS variables. On other systems, this is the same as
           $SHLINK.

       LDMODULECOMSTR
           If set, the string displayed when building loadable modules. If not set, then
           $LDMODULECOM (the command line) is displayed.

       LDMODULEEMITTER
           Contains the emitter specification for the LoadableModule builder. The manpage section
           "Builder Objects" contains general information on specifying emitters.

       LDMODULEFLAGS
           General user options passed to the linker for building loadable modules.

       LDMODULENOVERSIONSYMLINKS
           Instructs the LoadableModule builder to not automatically create symlinks for
           versioned modules. Defaults to $SHLIBNOVERSIONSYMLINKS

       LDMODULEPREFIX
           The prefix used for loadable module file names. On Mac OS X, this is null; on other
           systems, this is the same as $SHLIBPREFIX.

       _LDMODULESONAME
           A macro that automatically generates loadable module's SONAME based on $TARGET,
           $LDMODULEVERSION and $LDMODULESUFFIX. Used by LoadableModule builder when the linker
           tool supports SONAME (e.g.  gnulink).

       LDMODULESUFFIX
           The suffix used for loadable module file names. On Mac OS X, this is null; on other
           systems, this is the same as $SHLIBSUFFIX.

       LDMODULEVERSION
           When this construction variable is defined, a versioned loadable module is created by
           LoadableModule builder. This activates the $_LDMODULEVERSIONFLAGS and thus modifies
           the $LDMODULECOM as required, adds the version number to the library name, and creates
           the symlinks that are needed.  $LDMODULEVERSION versions should exist in the same
           format as $SHLIBVERSION.

       _LDMODULEVERSIONFLAGS
           This macro automatically introduces extra flags to $LDMODULECOM when building
           versioned LoadableModule (that is when $LDMODULEVERSION is set).
           _LDMODULEVERSIONFLAGS usually adds $SHLIBVERSIONFLAGS and some extra dynamically
           generated options (such as -Wl,-soname=$_LDMODULESONAME). It is unused by plain
           (unversioned) loadable modules.

       LDMODULEVERSIONFLAGS
           Extra flags added to $LDMODULECOM when building versioned LoadableModule. These flags
           are only used when $LDMODULEVERSION is set.

       LEX
           The lexical analyzer generator.

       LEX_HEADER_FILE
           If supplied, generate a C header file with the name taken from this variable. Will be
           emitted as a --header-file= command-line option. Use this in preference to including
           --header-file= in $LEXFLAGS directly.

       LEX_TABLES_FILE
           If supplied, write the lex tables to a file with the name taken from this variable.
           Will be emitted as a --tables-file= command-line option. Use this in preference to
           including --tables-file= in $LEXFLAGS directly.

       LEXCOM
           The command line used to call the lexical analyzer generator to generate a source
           file.

       LEXCOMSTR
           The string displayed when generating a source file using the lexical analyzer
           generator. If this is not set, then $LEXCOM (the command line) is displayed.

               env = Environment(LEXCOMSTR="Lex'ing $TARGET from $SOURCES")

       LEXFLAGS
           General options passed to the lexical analyzer generator. In addition to passing the
           value on during invocation, the lex tool also examines this construction variable for
           options which cause additional output files to be generated, and adds those to the
           target list. Recognized for this purpose are GNU flex options --header-file= and
           --tables-file=; the output file is named by the option argument.

           Note that files specified by --header-file= and --tables-file= may not be properly
           handled by SCons in all situations. Consider using $LEX_HEADER_FILE and
           $LEX_TABLES_FILE instead.

       LEXUNISTD
           Used only on windows environments to set a lex flag to prevent 'unistd.h' from being
           included. The default value is '--nounistd'.

       _LIBDIRFLAGS
           An automatically-generated construction variable containing the linker command-line
           options for specifying directories to be searched for library. The value of
           $_LIBDIRFLAGS is created by respectively prepending and appending $LIBDIRPREFIX and
           $LIBDIRSUFFIX to each directory in $LIBPATH.

       LIBDIRPREFIX
           The prefix used to specify a library directory on the linker command line. This will
           be prepended to each directory in the $LIBPATH construction variable when the
           $_LIBDIRFLAGS variable is automatically generated.

       LIBDIRSUFFIX
           The suffix used to specify a library directory on the linker command line. This will
           be appended to each directory in the $LIBPATH construction variable when the
           $_LIBDIRFLAGS variable is automatically generated.

       LIBEMITTER
           Contains the emitter specification for the StaticLibrary builder. The manpage section
           "Builder Objects" contains general information on specifying emitters.

       _LIBFLAGS
           An automatically-generated construction variable containing the linker command-line
           options for specifying libraries to be linked with the resulting target. The value of
           $_LIBFLAGS is created by respectively prepending and appending $LIBLINKPREFIX and
           $LIBLINKSUFFIX to each filename in $LIBS.

       LIBLINKPREFIX
           The prefix used to specify a library to link on the linker command line. This will be
           prepended to each library in the $LIBS construction variable when the $_LIBFLAGS
           variable is automatically generated.

       LIBLINKSUFFIX
           The suffix used to specify a library to link on the linker command line. This will be
           appended to each library in the $LIBS construction variable when the $_LIBFLAGS
           variable is automatically generated.

       LIBPATH
           The list of directories that will be searched for libraries specified by the $LIBS
           construction variable.  $LIBPATH should be a list of path strings, or a single string,
           not a pathname list joined by Python's os.sep.

           Do not put library search directives directly into $LINKFLAGS or $SHLINKFLAGS as the
           result will be non-portable.

           Note: directory names in $LIBPATH will be looked-up relative to the directory of the
           SConscript file when they are used in a command. To force scons to look-up a directory
           relative to the root of the source tree use the # prefix:

               env = Environment(LIBPATH='#/libs')

           The directory look-up can also be forced using the Dir function:

               libs = Dir('libs')
               env = Environment(LIBPATH=libs)

           The directory list will be added to command lines through the automatically-generated
           $_LIBDIRFLAGS construction variable, which is constructed by respectively prepending
           and appending the values of the $LIBDIRPREFIX and $LIBDIRSUFFIX construction variables
           to each directory in $LIBPATH. Any command lines you define that need the $LIBPATH
           directory list should include $_LIBDIRFLAGS:

               env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE")

       LIBPREFIX
           The prefix used for (static) library file names. A default value is set for each
           platform (posix, win32, os2, etc.), but the value is overridden by individual tools
           (ar, mslib, sgiar, sunar, tlib, etc.) to reflect the names of the libraries they
           create.

       LIBPREFIXES
           A list of all legal prefixes for library file names. When searching for library
           dependencies, SCons will look for files with these prefixes, the base library name,
           and suffixes from the $LIBSUFFIXES list.

       LIBS
           A list of one or more libraries that will be added to the link line for linking with
           any executable program, shared library, or loadable module created by the construction
           environment or override.

           String-valued library names should include only the library base names, without
           prefixes such as lib or suffixes such as .so or .dll. The library list will be added
           to command lines through the automatically-generated $_LIBFLAGS construction variable
           which is constructed by respectively prepending and appending the values of the
           $LIBLINKPREFIX and $LIBLINKSUFFIX construction variables to each library name in
           $LIBS. Library name strings should not include a path component, instead the compiler
           will be directed to look for libraries in the paths specified by $LIBPATH.

           Any command lines you define that need the $LIBS library list should include
           $_LIBFLAGS:

               env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE")

           If you add a File object to the $LIBS list, the name of that file will be added to
           $_LIBFLAGS, and thus to the link line, as-is, without $LIBLINKPREFIX or
           $LIBLINKSUFFIX. For example:

               env.Append(LIBS=File('/tmp/mylib.so'))

           In all cases, scons will add dependencies from the executable program to all the
           libraries in this list.

       LIBSUFFIX
           The suffix used for (static) library file names. A default value is set for each
           platform (posix, win32, os2, etc.), but the value is overridden by individual tools
           (ar, mslib, sgiar, sunar, tlib, etc.) to reflect the names of the libraries they
           create.

       LIBSUFFIXES
           A list of all legal suffixes for library file names. When searching for library
           dependencies, SCons will look for files with prefixes from the $LIBPREFIXES list, the
           base library name, and these suffixes.

       LICENSE
           The abbreviated name, preferably the SPDX code, of the license under which this
           project is released (GPL-3.0, LGPL-2.1, BSD-2-Clause etc.). See
           http://www.opensource.org/licenses/alphabetical[7] for a list of license names and
           SPDX codes.

           See the Package builder.

       LINESEPARATOR
           The separator used by the Substfile and Textfile builders. This value is used between
           sources when constructing the target. It defaults to the current system line
           separator.

       LINGUAS_FILE
           The $LINGUAS_FILE defines file(s) containing list of additional linguas to be
           processed by POInit, POUpdate or MOFiles builders. It also affects Translate builder.
           If the variable contains a string, it defines name of the list file. The $LINGUAS_FILE
           may be a list of file names as well. If $LINGUAS_FILE is set to True (or non-zero
           numeric value), the list will be read from default file named LINGUAS.

       LINK
           The linker. See also $SHLINK for linking shared objects.

           On POSIX systems (those using the link tool), you should normally not change this
           value as it defaults to a "smart" linker tool which selects a compiler driver matching
           the type of source files in use. So for example, if you set $CXX to a specific
           compiler name, and are compiling C++ sources, the smartlink function will
           automatically select the same compiler for linking.

       LINKCOM
           The command line used to link object files into an executable. See also $SHLINKCOM for
           linking shared objects.

       LINKCOMSTR
           If set, the string displayed when object files are linked into an executable. If not
           set, then $LINKCOM (the command line) is displayed. See also $SHLINKCOMSTR. for
           linking shared objects.

               env = Environment(LINKCOMSTR = "Linking $TARGET")

       LINKFLAGS
           General user options passed to the linker. Note that this variable should not contain
           -l (or similar) options for linking with the libraries listed in $LIBS, nor -L (or
           similar) library search path options that scons generates automatically from $LIBPATH.
           See $_LIBFLAGS above, for the variable that expands to library-link options, and
           $_LIBDIRFLAGS above, for the variable that expands to library search path options. See
           also $SHLINKFLAGS. for linking shared objects.

       M4
           The M4 macro preprocessor.

       M4COM
           The command line used to pass files through the M4 macro preprocessor.

       M4COMSTR
           The string displayed when a file is passed through the M4 macro preprocessor. If this
           is not set, then $M4COM (the command line) is displayed.

       M4FLAGS
           General options passed to the M4 macro preprocessor.

       MAKEINDEX
           The makeindex generator for the TeX formatter and typesetter and the LaTeX structured
           formatter and typesetter.

       MAKEINDEXCOM
           The command line used to call the makeindex generator for the TeX formatter and
           typesetter and the LaTeX structured formatter and typesetter.

       MAKEINDEXCOMSTR
           The string displayed when calling the makeindex generator for the TeX formatter and
           typesetter and the LaTeX structured formatter and typesetter. If this is not set, then
           $MAKEINDEXCOM (the command line) is displayed.

       MAKEINDEXFLAGS
           General options passed to the makeindex generator for the TeX formatter and typesetter
           and the LaTeX structured formatter and typesetter.

       MAXLINELENGTH
           The maximum number of characters allowed on an external command line. On Win32
           systems, link lines longer than this many characters are linked via a temporary file
           name.

       MIDL
           The Microsoft IDL compiler.

       MIDLCOM
           The command line used to pass files to the Microsoft IDL compiler.

       MIDLCOMSTR
           The string displayed when the Microsoft IDL compiler is called. If this is not set,
           then $MIDLCOM (the command line) is displayed.

       MIDLFLAGS
           General options passed to the Microsoft IDL compiler.

       MOSUFFIX
           Suffix used for MO files (default: '.mo'). See msgfmt tool and MOFiles builder.

       MSGFMT
           Absolute path to msgfmt(1) binary, found by Detect(). See msgfmt tool and MOFiles
           builder.

       MSGFMTCOM
           Complete command line to run msgfmt(1) program. See msgfmt tool and MOFiles builder.

       MSGFMTCOMSTR
           String to display when msgfmt(1) is invoked (default: '', which means ``print
           $MSGFMTCOM''). See msgfmt tool and MOFiles builder.

       MSGFMTFLAGS
           Additional flags to msgfmt(1). See msgfmt tool and MOFiles builder.

       MSGINIT
           Path to msginit(1) program (found via Detect()). See msginit tool and POInit builder.

       MSGINITCOM
           Complete command line to run msginit(1) program. See msginit tool and POInit builder.

       MSGINITCOMSTR
           String to display when msginit(1) is invoked (default: '', which means ``print
           $MSGINITCOM''). See msginit tool and POInit builder.

       MSGINITFLAGS
           List of additional flags to msginit(1) (default: []). See msginit tool and POInit
           builder.

       _MSGINITLOCALE
           Internal ``macro''. Computes locale (language) name based on target filename (default:
           '${TARGET.filebase}').

           See msginit tool and POInit builder.

       MSGMERGE
           Absolute path to msgmerge(1) binary as found by Detect(). See msgmerge tool and
           POUpdate builder.

       MSGMERGECOM
           Complete command line to run msgmerge(1) command. See msgmerge tool and POUpdate
           builder.

       MSGMERGECOMSTR
           String to be displayed when msgmerge(1) is invoked (default: '', which means ``print
           $MSGMERGECOM''). See msgmerge tool and POUpdate builder.

       MSGMERGEFLAGS
           Additional flags to msgmerge(1) command. See msgmerge tool and POUpdate builder.

       MSSDK_DIR
           The directory containing the Microsoft SDK (either Platform SDK or Windows SDK) to be
           used for compilation.

       MSSDK_VERSION
           The version string of the Microsoft SDK (either Platform SDK or Windows SDK) to be
           used for compilation. Supported versions include 6.1, 6.0A, 6.0, 2003R2 and 2003R1.

       MSVC_BATCH
           When set to any true value, specifies that SCons should batch compilation of object
           files when calling the Microsoft Visual C/C++ compiler. All compilations of source
           files from the same source directory that generate target files in a same output
           directory and were configured in SCons using the same construction environment will be
           built in a single call to the compiler. Only source files that have changed since
           their object files were built will be passed to each compiler invocation (via the
           $CHANGED_SOURCES construction variable). Any compilations where the object (target)
           file base name (minus the .obj) does not match the source file base name will be
           compiled separately.

       MSVC_NOTFOUND_POLICY
           Specify the scons behavior when the Microsoft Visual C/C++ compiler is not detected.

           The $MSVC_NOTFOUND_POLICY specifies the scons behavior when no msvc versions are
           detected or when the requested msvc version is not detected.

           The valid values for $MSVC_NOTFOUND_POLICY and the corresponding scons behavior are:

           'Error' or 'Exception'
               Raise an exception when no msvc versions are detected or when the requested msvc
               version is not detected.

           'Warning' or 'Warn'
               Issue a warning and continue when no msvc versions are detected or when the
               requested msvc version is not detected. Depending on usage, this could result in
               build failure(s).

           'Ignore' or 'Suppress'
               Take no action and continue when no msvc versions are detected or when the
               requested msvc version is not detected. Depending on usage, this could result in
               build failure(s).

           Note: in addition to the camel case values shown above, lower case and upper case
           values are accepted as well.

           The $MSVC_NOTFOUND_POLICY is applied when any of the following conditions are
           satisfied:

           •    $MSVC_VERSION is specified, the default tools list is implicitly defined (i.e.,
               the tools list is not specified), and the default tools list contains one or more
               of the msvc tools.

           •    $MSVC_VERSION is specified, the default tools list is explicitly specified (e.g.,
               tools=['default']), and the default tools list contains one or more of the msvc
               tools.

           •   A non-default tools list is specified that contains one or more of the msvc tools
               (e.g., tools=['msvc', 'mslink']).

           The $MSVC_NOTFOUND_POLICY is ignored when any of the following conditions are
           satisfied:

           •    $MSVC_VERSION is not specified and the default tools list is implicitly defined
               (i.e., the tools list is not specified).

           •    $MSVC_VERSION is not specified and the default tools list is explicitly specified
               (e.g., tools=['default']).

           •   A non-default tool list is specified that does not contain any of the msvc tools
               (e.g., tools=['mingw']).

           Important usage details:

           •    $MSVC_NOTFOUND_POLICY must be passed as an argument to the Environment
               constructor when an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default
               tools list or via a tools list passed to the Environment constructor. Otherwise,
               $MSVC_NOTFOUND_POLICY must be set before the first msvc tool is loaded into the
               environment.

           When $MSVC_NOTFOUND_POLICY is not specified, the default scons behavior is to issue a
           warning and continue subject to the conditions listed above. The default scons
           behavior may change in the future.

           New in version 4.4

       MSVC_SCRIPT_ARGS
           Pass user-defined arguments to the Visual C++ batch file determined via autodetection.

           $MSVC_SCRIPT_ARGS is available for msvc batch file arguments that do not have
           first-class support via construction variables or when there is an issue with the
           appropriate construction variable validation. When available, it is recommended to use
           the appropriate construction variables (e.g., $MSVC_TOOLSET_VERSION) rather than
           $MSVC_SCRIPT_ARGS arguments.

           The valid values for $MSVC_SCRIPT_ARGS are: None, a string, or a list of strings.

           The $MSVC_SCRIPT_ARGS value is converted to a scalar string (i.e., "flattened"). The
           resulting scalar string, if not empty, is passed as an argument to the msvc batch file
           determined via autodetection subject to the validation conditions listed below.

           $MSVC_SCRIPT_ARGS is ignored when the value is None and when the result from argument
           conversion is an empty string. The validation conditions below do not apply.

           An exception is raised when any of the following conditions are satisfied:

           •    $MSVC_SCRIPT_ARGS is specified for Visual Studio 2013 and earlier.

           •   Multiple SDK version arguments (e.g., '10.0.20348.0') are specified in
               $MSVC_SCRIPT_ARGS.

           •    $MSVC_SDK_VERSION is specified and an SDK version argument (e.g., '10.0.20348.0')
               is specified in $MSVC_SCRIPT_ARGS. Multiple SDK version declarations via
               $MSVC_SDK_VERSION and $MSVC_SCRIPT_ARGS are not allowed.

           •   Multiple toolset version arguments (e.g., '-vcvars_ver=14.29') are specified in
               $MSVC_SCRIPT_ARGS.

           •    $MSVC_TOOLSET_VERSION is specified and a toolset version argument (e.g.,
               '-vcvars_ver=14.29') is specified in $MSVC_SCRIPT_ARGS. Multiple toolset version
               declarations via $MSVC_TOOLSET_VERSION and $MSVC_SCRIPT_ARGS are not allowed.

           •   Multiple spectre library arguments (e.g., '-vcvars_spectre_libs=spectre') are
               specified in $MSVC_SCRIPT_ARGS.

           •    $MSVC_SPECTRE_LIBS is enabled and a spectre library argument (e.g.,
               '-vcvars_spectre_libs=spectre') is specified in $MSVC_SCRIPT_ARGS. Multiple
               spectre library declarations via $MSVC_SPECTRE_LIBS and $MSVC_SCRIPT_ARGS are not
               allowed.

           •   Multiple UWP arguments (e.g., uwp or store) are specified in $MSVC_SCRIPT_ARGS.

           •    $MSVC_UWP_APP is enabled and a UWP argument (e.g., uwp or store) is specified in
               $MSVC_SCRIPT_ARGS. Multiple UWP declarations via $MSVC_UWP_APP and
               $MSVC_SCRIPT_ARGS are not allowed.

           Example 1 - A Visual Studio 2022 build with an SDK version and a toolset version
           specified with a string argument:

               env = Environment(MSVC_VERSION='14.3', MSVC_SCRIPT_ARGS='10.0.20348.0 -vcvars_ver=14.29.30133')

           Example 2 - A Visual Studio 2022 build with an SDK version and a toolset version
           specified with a list argument:

               env = Environment(MSVC_VERSION='14.3', MSVC_SCRIPT_ARGS=['10.0.20348.0', '-vcvars_ver=14.29.30133'])

           Important usage details:

           •    $MSVC_SCRIPT_ARGS must be passed as an argument to the Environment constructor
               when an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default tools list or
               via a tools list passed to the Environment constructor. Otherwise,
               $MSVC_SCRIPT_ARGS must be set before the first msvc tool is loaded into the
               environment.

           •   Other than checking for multiple declarations as described above,
               $MSVC_SCRIPT_ARGS arguments are not validated.

           •
                Erroneous, inconsistent, and/or version incompatible $MSVC_SCRIPT_ARGS arguments
               are likely to result in build failures for reasons that are not readily apparent
               and may be difficult to diagnose.  The burden is on the user to ensure that the
               arguments provided to the msvc batch file are valid, consistent and compatible
               with the version of msvc selected.

           New in version 4.4

       MSVC_SCRIPTERROR_POLICY
           Specify the scons behavior when Microsoft Visual C/C++ batch file errors are detected.

           The $MSVC_SCRIPTERROR_POLICY specifies the scons behavior when msvc batch file errors
           are detected. When $MSVC_SCRIPTERROR_POLICY is not specified, the default scons
           behavior is to suppress msvc batch file error messages.

           The root cause of msvc build failures may be difficult to diagnose. In these
           situations, setting the scons behavior to issue a warning when msvc batch file errors
           are detected may produce additional diagnostic information.

           The valid values for $MSVC_SCRIPTERROR_POLICY and the corresponding scons behavior
           are:

           'Error' or 'Exception'
               Raise an exception when msvc batch file errors are detected.

           'Warning' or 'Warn'
               Issue a warning when msvc batch file errors are detected.

           'Ignore' or 'Suppress'
               Suppress msvc batch file error messages.

               New in version 4.4

           Note: in addition to the camel case values shown above, lower case and upper case
           values are accepted as well.

           Example 1 - A Visual Studio 2022 build with user-defined script arguments:

               env = environment(MSVC_VERSION='14.3', MSVC_SCRIPT_ARGS=['8.1', 'store', '-vcvars_ver=14.1'])
               env.Program('hello', ['hello.c'], CCFLAGS='/MD', LIBS=['kernel32', 'user32', 'runtimeobject'])

           Example 1 - Output fragment:

               ...
               link /nologo /OUT:_build001\hello.exe kernel32.lib user32.lib runtimeobject.lib _build001\hello.obj
               LINK : fatal error LNK1104: cannot open file 'MSVCRT.lib'
               ...

           Example 2 - A Visual Studio 2022 build with user-defined script arguments and the
           script error policy set to issue a warning when msvc batch file errors are detected:

               env = environment(MSVC_VERSION='14.3', MSVC_SCRIPT_ARGS=['8.1', 'store', '-vcvars_ver=14.1'], MSVC_SCRIPTERROR_POLICY='warn')
               env.Program('hello', ['hello.c'], CCFLAGS='/MD', LIBS=['kernel32', 'user32', 'runtimeobject'])

           Example 2 - Output fragment:

               ...
               scons: warning: vc script errors detected:
               [ERROR:vcvars.bat] The UWP Application Platform requires a Windows 10 SDK.
               [ERROR:vcvars.bat] WindowsSdkDir = "C:\Program Files (x86)\Windows Kits\8.1\"
               [ERROR:vcvars.bat] host/target architecture is not supported : { x64 , x64 }
               ...
               link /nologo /OUT:_build001\hello.exe kernel32.lib user32.lib runtimeobject.lib _build001\hello.obj
               LINK : fatal error LNK1104: cannot open file 'MSVCRT.lib'

           Important usage details:

           •    $MSVC_SCRIPTERROR_POLICY must be passed as an argument to the Environment
               constructor when an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default
               tools list or via a tools list passed to the Environment constructor. Otherwise,
               $MSVC_SCRIPTERROR_POLICY must be set before the first msvc tool is loaded into the
               environment.

           •   Due to scons implementation details, not all Windows system environment variables
               are propagated to the environment in which the msvc batch file is executed.
               Depending on Visual Studio version and installation options, non-fatal msvc batch
               file error messages may be generated for ancillary tools which may not affect
               builds with the msvc compiler. For this reason, caution is recommended when
               setting the script error policy to raise an exception (e.g., 'Error').

           New in version 4.4

       MSVC_SDK_VERSION
           Build with a specific version of the Microsoft Software Development Kit (SDK).

           The valid values for $MSVC_SDK_VERSION are: None or a string containing the requested
           SDK version (e.g., '10.0.20348.0').

           $MSVC_SDK_VERSION is ignored when the value is None and when the value is an empty
           string. The validation conditions below do not apply.

           An exception is raised when any of the following conditions are satisfied:

           •    $MSVC_SDK_VERSION is specified for Visual Studio 2013 and earlier.

           •    $MSVC_SDK_VERSION is specified and an SDK version argument is specified in
               $MSVC_SCRIPT_ARGS. Multiple SDK version declarations via $MSVC_SDK_VERSION and
               $MSVC_SCRIPT_ARGS are not allowed.

           •   The $MSVC_SDK_VERSION specified does not match any of the supported formats:

               •    '10.0.XXXXX.Y' [SDK 10.0]

               •    '8.1' [SDK 8.1]

           •   The system folder for the corresponding $MSVC_SDK_VERSION version is not found.
               The requested SDK version does not appear to be installed.

           •   The $MSVC_SDK_VERSION version does not appear to support the requested platform
               type (i.e., UWP or Desktop). The requested SDK version platform type components do
               not appear to be installed.

           •   The $MSVC_SDK_VERSION version is 8.1, the platform type is UWP, and the build
               tools selected are from Visual Studio 2017 and later (i.e., $MSVC_VERSION must be
               '14.0' or $MSVC_TOOLSET_VERSION must be '14.0').

           Example 1 - A Visual Studio 2022 build with a specific Windows SDK version:

               env = Environment(MSVC_VERSION='14.3', MSVC_SDK_VERSION='10.0.20348.0')

           Example 2 - A Visual Studio 2022 build with a specific SDK version for the Universal
           Windows Platform:

               env = Environment(MSVC_VERSION='14.3', MSVC_SDK_VERSION='10.0.20348.0', MSVC_UWP_APP=True)

           Important usage details:

           •    $MSVC_SDK_VERSION must be passed as an argument to the Environment constructor
               when an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default tools list or
               via a tools list passed to the Environment constructor. Otherwise,
               $MSVC_SDK_VERSION must be set before the first msvc tool is loaded into the
               environment.

           •    Should a SDK 10.0 version be installed that does not follow the naming scheme
               above, the SDK version will need to be specified via $MSVC_SCRIPT_ARGS until the
               version number validation format can be extended.

           •   Should an exception be raised indicating that the SDK version is not found, verify
               that the requested SDK version is installed with the necessary platform type
               components.

           •   There is a known issue with the Microsoft libraries when the target architecture
               is ARM64 and a Windows 11 SDK (version '10.0.22000.0' and later) is used with the
               v141 build tools and older v142 toolsets (versions '14.28.29333' and earlier).
               Should build failures arise with these combinations of settings due to unresolved
               symbols in the Microsoft libraries, $MSVC_SDK_VERSION may be employed to specify a
               Windows 10 SDK (e.g., '10.0.20348.0') for the build.

           New in version 4.4

       MSVC_SPECTRE_LIBS
           Build with the spectre-mitigated Visual C++ libraries.

           The valid values for $MSVC_SPECTRE_LIBS are: True, False, or None.

           When $MSVC_SPECTRE_LIBS is enabled (i.e., True), the Visual C++ environment will
           include the paths to the spectre-mitigated implementations of the Microsoft Visual C++
           libraries.

           An exception is raised when any of the following conditions are satisfied:

           •    $MSVC_SPECTRE_LIBS is enabled for Visual Studio 2015 and earlier.

           •    $MSVC_SPECTRE_LIBS is enabled and a spectre library argument is specified in
               $MSVC_SCRIPT_ARGS. Multiple spectre library declarations via $MSVC_SPECTRE_LIBS
               and $MSVC_SCRIPT_ARGS are not allowed.

           •    $MSVC_SPECTRE_LIBS is enabled and the platform type is UWP. There are no
               spectre-mitigated libraries for Universal Windows Platform (UWP) applications or
               components.

           Example - A Visual Studio 2022 build with spectre mitigated Visual C++ libraries:

               env = Environment(MSVC_VERSION='14.3', MSVC_SPECTRE_LIBS=True)

           Important usage details:

           •    $MSVC_SPECTRE_LIBS must be passed as an argument to the Environment constructor
               when an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default tools list or
               via a tools list passed to the Environment constructor. Otherwise,
               $MSVC_SPECTRE_LIBS must be set before the first msvc tool is loaded into the
               environment.

           •   Additional compiler switches (e.g., /Qspectre) are necessary for including spectre
               mitigations when building user artifacts. Refer to the Visual Studio documentation
               for details.

           •
                The existence of the spectre libraries host architecture and target architecture
               folders are not verified when $MSVC_SPECTRE_LIBS is enabled which could result in
               build failures.  The burden is on the user to ensure the requisite libraries with
               spectre mitigations are installed.

           New in version 4.4

       MSVC_TOOLSET_VERSION
           Build with a specific Visual C++ toolset version.

            Specifying $MSVC_TOOLSET_VERSION does not affect the autodetection and selection of
           msvc instances. The $MSVC_TOOLSET_VERSION is applied after an msvc instance is
           selected. This could be the default version of msvc if $MSVC_VERSION is not specified.

           The valid values for $MSVC_TOOLSET_VERSION are: None or a string containing the
           requested toolset version (e.g., '14.29').

           $MSVC_TOOLSET_VERSION is ignored when the value is None and when the value is an empty
           string. The validation conditions below do not apply.

           An exception is raised when any of the following conditions are satisfied:

           •    $MSVC_TOOLSET_VERSION is specified for Visual Studio 2015 and earlier.

           •    $MSVC_TOOLSET_VERSION is specified and a toolset version argument is specified in
               $MSVC_SCRIPT_ARGS. Multiple toolset version declarations via $MSVC_TOOLSET_VERSION
               and $MSVC_SCRIPT_ARGS are not allowed.

           •   The $MSVC_TOOLSET_VERSION specified does not match any of the supported formats:

               •    'XX.Y'

               •    'XX.YY'

               •    'XX.YY.ZZZZZ'

               •    'XX.YY.Z' to 'XX.YY.ZZZZ'
                    [scons extension not directly supported by the msvc batch files and may be
                   removed in the future]

               •    'XX.YY.ZZ.N' [SxS format]

               •    'XX.YY.ZZ.NN' [SxS format]

           •   The major msvc version prefix (i.e., 'XX.Y') of the $MSVC_TOOLSET_VERSION
               specified is for Visual Studio 2013 and earlier (e.g., '12.0').

           •   The major msvc version prefix (i.e., 'XX.Y') of the $MSVC_TOOLSET_VERSION
               specified is greater than the msvc version selected (e.g., '99.0').

           •   A system folder for the corresponding $MSVC_TOOLSET_VERSION version is not found.
               The requested toolset version does not appear to be installed.

           Toolset selection details:

           •   When $MSVC_TOOLSET_VERSION is not an SxS version number or a full toolset version
               number: the first toolset version, ranked in descending order, that matches the
               $MSVC_TOOLSET_VERSION prefix is selected.

           •   When $MSVC_TOOLSET_VERSION is specified using the major msvc version prefix (i.e.,
               'XX.Y') and the major msvc version is that of the latest release of Visual Studio,
               the selected toolset version may not be the same as the default Visual C++ toolset
               version.

               In the latest release of Visual Studio, the default Visual C++ toolset version is
               not necessarily the toolset with the largest version number.

           Example 1 - A default Visual Studio build with a partial toolset version specified:

               env = Environment(MSVC_TOOLSET_VERSION='14.2')

           Example 2 - A default Visual Studio build with a partial toolset version specified:

               env = Environment(MSVC_TOOLSET_VERSION='14.29')

           Example 3 - A Visual Studio 2022 build with a full toolset version specified:

               env = Environment(MSVC_VERSION='14.3', MSVC_TOOLSET_VERSION='14.29.30133')

           Example 4 - A Visual Studio 2022 build with an SxS toolset version specified:

               env = Environment(MSVC_VERSION='14.3', MSVC_TOOLSET_VERSION='14.29.16.11')

           Important usage details:

           •    $MSVC_TOOLSET_VERSION must be passed as an argument to the Environment
               constructor when an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default
               tools list or via a tools list passed to the Environment constructor. Otherwise,
               $MSVC_TOOLSET_VERSION must be set before the first msvc tool is loaded into the
               environment.

           •
                The existence of the toolset host architecture and target architecture folders
               are not verified when $MSVC_TOOLSET_VERSION is specified which could result in
               build failures.  The burden is on the user to ensure the requisite toolset target
               architecture build tools are installed.

           New in version 4.4

       MSVC_USE_SCRIPT
           Use a batch script to set up the Microsoft Visual C++ compiler.

           If set to the name of a Visual Studio .bat file (e.g.  vcvars.bat), SCons will run
           that batch file instead of the auto-detected one, and extract the relevant variables
           from the result (typically %INCLUDE%, %LIB%, and %PATH%) for supplying to the build.
           This can be useful to force the use of a compiler version that SCons does not detect.
           $MSVC_USE_SCRIPT_ARGS provides arguments passed to this script.

           Setting $MSVC_USE_SCRIPT to None bypasses the Visual Studio autodetection entirely;
           use this if you are running SCons in a Visual Studio cmd window and importing the
           shell's environment variables - that is, if you are sure everything is set correctly
           already and you don't want SCons to change anything.

           $MSVC_USE_SCRIPT ignores $MSVC_VERSION and $TARGET_ARCH.

           Changed in version 4.4: new $MSVC_USE_SCRIPT_ARGS provides a way to pass arguments.

       MSVC_USE_SCRIPT_ARGS
           Provides arguments passed to the script $MSVC_USE_SCRIPT.

           New in version 4.4

       MSVC_USE_SETTINGS
           Use a dictionary to set up the Microsoft Visual C++ compiler.

           $MSVC_USE_SETTINGS is ignored when $MSVC_USE_SCRIPT is defined and/or when
           $MSVC_USE_SETTINGS is set to None.

           The dictionary is used to populate the environment with the relevant variables
           (typically %INCLUDE%, %LIB%, and %PATH%) for supplying to the build. This can be
           useful to force the use of a compiler environment that SCons does not configure
           correctly. This is an alternative to manually configuring the environment when
           bypassing Visual Studio autodetection entirely by setting $MSVC_USE_SCRIPT to None.

           Here is an example of configuring a build environment using the Microsoft Visual C/C++
           compiler included in the Microsoft SDK on a 64-bit host and building for a 64-bit
           architecture:

               # Microsoft SDK 6.0 (MSVC 8.0): 64-bit host and 64-bit target
               msvc_use_settings = {
                   "PATH": [
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\VC\\Bin\\x64",
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\Bin\\x64",
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\Bin",
                       "C:\\Windows\\Microsoft.NET\\Framework\\v2.0.50727",
                       "C:\\Windows\\system32",
                       "C:\\Windows",
                       "C:\\Windows\\System32\\Wbem",
                       "C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\"
                   ],
                   "INCLUDE": [
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\VC\\Include",
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\VC\\Include\\Sys",
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\Include",
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\Include\\gl",
                   ],
                   "LIB": [
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\VC\\Lib\\x64",
                       "C:\\Program Files\\Microsoft SDKs\\Windows\\v6.0\\Lib\\x64",
                   ],
                   "LIBPATH": [],
                   "VSCMD_ARG_app_plat": [],
                   "VCINSTALLDIR": [],
                   "VCToolsInstallDir": []
               }

               # Specifying MSVC_VERSION is recommended
               env = Environment(MSVC_VERSION='8.0', MSVC_USE_SETTINGS=msvc_use_settings)

           Important usage details:

           •    $MSVC_USE_SETTINGS must be passed as an argument to the Environment constructor
               when an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default tools list or
               via a tools list passed to the Environment constructor. Otherwise,
               $MSVC_USE_SETTINGS must be set before the first msvc tool is loaded into the
               environment.

           •
                The dictionary content requirements are based on the internal msvc implementation
               and therefore may change at any time.  The burden is on the user to ensure the
               dictionary contents are minimally sufficient to ensure successful builds.

           New in version 4.4

       MSVC_UWP_APP
           Build with the Universal Windows Platform (UWP) application Visual C++ libraries.

           The valid values for $MSVC_UWP_APP are: True, '1', False, '0', or None.

           When $MSVC_UWP_APP is enabled (i.e., True or '1'), the Visual C++ environment will be
           set up to point to the Windows Store compatible libraries and Visual C++ runtimes. In
           doing so, any libraries that are built will be able to be used in a UWP App and
           published to the Windows Store.

           An exception is raised when any of the following conditions are satisfied:

           •    $MSVC_UWP_APP is enabled for Visual Studio 2013 and earlier.

           •    $MSVC_UWP_APP is enabled and a UWP argument is specified in $MSVC_SCRIPT_ARGS.
               Multiple UWP declarations via $MSVC_UWP_APP and $MSVC_SCRIPT_ARGS are not allowed.

           Example - A Visual Studio 2022 build for the Universal Windows Platform:

               env = Environment(MSVC_VERSION='14.3', MSVC_UWP_APP=True)

           Important usage details:

           •    $MSVC_UWP_APP must be passed as an argument to the Environment constructor when
               an msvc tool (e.g., msvc, msvs, etc.) is loaded via the default tools list or via
               a tools list passed to the Environment constructor. Otherwise, $MSVC_UWP_APP must
               be set before the first msvc tool is loaded into the environment.

           •
                The existence of the UWP libraries is not verified when $MSVC_UWP_APP is enabled
               which could result in build failures.  The burden is on the user to ensure the
               requisite UWP libraries are installed.

       MSVC_VERSION
           Sets the preferred version of Microsoft Visual C/C++ to use. If the specified version
           is unavailable (not installed, or not discoverable), tool initialization will fail. If
           $MSVC_VERSION is not set, SCons will (by default) select the latest version of Visual
           C/C++ installed on your system.

           $MSVC_VERSION must be passed as an argument to the Environment constructor when an
           msvc tool (e.g., msvc, msvs, etc.) is loaded via the default tools list or via a tools
           list passed to the Environment constructor. Otherwise, $MSVC_VERSION must be set
           before the first msvc tool is loaded into the environment.

           The valid values for $MSVC_VERSION represent major versions of the compiler, except
           that versions ending in Exp refer to "Express" or "Express for Desktop" Visual Studio
           editions, which require distict entries because they use a different filesystem layout
           and have some feature limitations compared to the full version. The following table
           shows correspondence of the selector string to various version indicators ('x' is used
           as a placeholder for a single digit that can vary). Note that it is not necessary to
           install Visual Studio to build with SCons (for example, you can install only Build
           Tools), but if Visual Studio is installed, additional builders such as MSVSSolution
           and MSVSProject become avaialable and will correspond to the indicated versions.

           ┌──────────┬────────────────┬───────────┬───────────────┬─────────────┐
           │SCons Key │ MSVC++ Version │ _MSVC_VER │ VS Product    │ MSBuild/VS  │
           │          │                │           │               │ Version     │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │14.3      │     14.3x      │   193x    │ Visual Studio │    17.x     │
           │          │                │           │ 2022          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │14.2      │     14.2x      │   192x    │ Visual Studio │ 16.x, 16.1x │
           │          │                │           │ 2019          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │14.1      │ 14.1 or 14.1x  │   191x    │ Visual Studio │    15.x     │
           │          │                │           │ 2017          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │14.1Exp   │      14.1      │   1910    │ Visual Studio │    15.0     │
           │          │                │           │ 2017 Express  │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │14.0      │      14.0      │   1900    │ Visual Studio │    14.0     │
           │          │                │           │ 2015          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │14.0Exp   │      14.0      │   1900    │ Visual Studio │    14.0     │
           │          │                │           │ 2015 Express  │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │12.0      │      12.0      │   1800    │ Visual Studio │    12.0     │
           │          │                │           │ 2013          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │12.0Exp   │      12.0      │   1800    │ Visual Studio │    12.0     │
           │          │                │           │ 2013 Express  │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │11.0      │      11.0      │   1700    │ Visual Studio │    11.0     │
           │          │                │           │ 2012          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │11.0Exp   │      11.0      │   1700    │ Visual Studio │    11.0     │
           │          │                │           │ 2012 Express  │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │10.0      │      10.0      │   1600    │ Visual Studio │    10.0     │
           │          │                │           │ 2010          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │10.0Exp   │      10.0      │   1600    │ Visual C++    │    10.0     │
           │          │                │           │ Express 2010  │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │9.0       │      9.0       │   1500    │ Visual Studio │     9.0     │
           │          │                │           │ 2008          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │9.0Exp    │      9.0       │   1500    │ Visual C++    │     9.0     │
           │          │                │           │ Express 2008  │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │8.0       │      8.0       │   1400    │ Visual Studio │     8.0     │
           │          │                │           │ 2005          │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │8.0Exp    │      8.0       │   1400    │ Visual C++    │     8.0     │
           │          │                │           │ Express 2005  │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │7.1       │      7.1       │   1300    │ Visual Studio │     7.1     │
           │          │                │           │ .NET 2003     │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │7.0       │      7.0       │   1200    │ Visual Studio │     7.0     │
           │          │                │           │ .NET 2002     │             │
           ├──────────┼────────────────┼───────────┼───────────────┼─────────────┤
           │6.0       │      6.0       │   1100    │ Visual Studio │     6.0     │
           │          │                │           │ 6.0           │             │
           └──────────┴────────────────┴───────────┴───────────────┴─────────────┘
           The compilation environment can be further or more precisely specified through the use
           of several other construction variables: see the descriptions of
           $MSVC_TOOLSET_VERSION, $MSVC_SDK_VERSION, $MSVC_USE_SCRIPT, $MSVC_USE_SCRIPT_ARGS, and
           $MSVC_USE_SETTINGS.

       MSVS
           When the Microsoft Visual Studio tools are initialized, they set up this dictionary
           with the following keys:

           VERSION
               the version of MSVS being used (can be set via $MSVC_VERSION)

           VERSIONS
               the available versions of MSVS installed

           VCINSTALLDIR
               installed directory of Visual C++

           VSINSTALLDIR
               installed directory of Visual Studio

           FRAMEWORKDIR
               installed directory of the .NET framework

           FRAMEWORKVERSIONS
               list of installed versions of the .NET framework, sorted latest to oldest.

           FRAMEWORKVERSION
               latest installed version of the .NET framework

           FRAMEWORKSDKDIR
               installed location of the .NET SDK.

           PLATFORMSDKDIR
               installed location of the Platform SDK.

           PLATFORMSDK_MODULES
               dictionary of installed Platform SDK modules, where the dictionary keys are
               keywords for the various modules, and the values are 2-tuples where the first is
               the release date, and the second is the version number.

           If a value is not set, it was not available in the registry. Visual Studio 2017 and
           later do not use the registry for primary storage of this information, so typically
           for these versions only PROJECTSUFFIX and SOLUTIONSUFFIX will be set.

       MSVS_ARCH
           Sets the architecture for which the generated project(s) should build.

           The default value is x86.  amd64 is also supported by SCons for most Visual Studio
           versions. Since Visual Studio 2015 arm is supported, and since Visual Studio 2017
           arm64 is supported. Trying to set $MSVS_ARCH to an architecture that's not supported
           for a given Visual Studio version will generate an error.

       MSVS_PROJECT_GUID
           The string placed in a generated Microsoft Visual C++ project file as the value of the
           ProjectGUID attribute. There is no default value. If not defined, a new GUID is
           generated.

       MSVS_SCC_AUX_PATH
           The path name placed in a generated Microsoft Visual C++ project file as the value of
           the SccAuxPath attribute if the MSVS_SCC_PROVIDER construction variable is also set.
           There is no default value.

       MSVS_SCC_CONNECTION_ROOT
           The root path of projects in your SCC workspace, i.e the path under which all project
           and solution files will be generated. It is used as a reference path from which the
           relative paths of the generated Microsoft Visual C++ project and solution files are
           computed. The relative project file path is placed as the value of the SccLocalPath
           attribute of the project file and as the values of the
           SccProjectFilePathRelativizedFromConnection[i] (where [i] ranges from 0 to the number
           of projects in the solution) attributes of the GlobalSection(SourceCodeControl)
           section of the Microsoft Visual Studio solution file. Similarly the relative solution
           file path is placed as the values of the SccLocalPath[i] (where [i] ranges from 0 to
           the number of projects in the solution) attributes of the
           GlobalSection(SourceCodeControl) section of the Microsoft Visual Studio solution file.
           This is used only if the MSVS_SCC_PROVIDER construction variable is also set. The
           default value is the current working directory.

       MSVS_SCC_PROJECT_NAME
           The project name placed in a generated Microsoft Visual C++ project file as the value
           of the SccProjectName attribute if the MSVS_SCC_PROVIDER construction variable is also
           set. In this case the string is also placed in the SccProjectName0 attribute of the
           GlobalSection(SourceCodeControl) section of the Microsoft Visual Studio solution file.
           There is no default value.

       MSVS_SCC_PROVIDER
           The string placed in a generated Microsoft Visual C++ project file as the value of the
           SccProvider attribute. The string is also placed in the SccProvider0 attribute of the
           GlobalSection(SourceCodeControl) section of the Microsoft Visual Studio solution file.
           There is no default value.

       MSVS_VERSION
           Set the preferred version of Microsoft Visual Studio to use.

           If $MSVS_VERSION is not set, SCons will (by default) select the latest version of
           Visual Studio installed on your system. So, if you have version 6 and version 7 (MSVS
           .NET) installed, it will prefer version 7. You can override this by specifying the
           $MSVS_VERSION variable when initializing the Environment, setting it to the
           appropriate version ('6.0' or '7.0', for example). If the specified version isn't
           installed, tool initialization will fail.

           Deprecated since 1.3.0: $MSVS_VERSION is deprecated in favor of $MSVC_VERSION. As a
           transitional aid, if $MSVS_VERSION is set and $MSVC_VERSION is not, $MSVC_VERSION will
           be initialized to the value of $MSVS_VERSION. An error is raised if If both are set
           and have different values,

       MSVSBUILDCOM
           The build command line placed in a generated Microsoft Visual C++ project file. The
           default is to have Visual Studio invoke SCons with any specified build targets.

       MSVSCLEANCOM
           The clean command line placed in a generated Microsoft Visual C++ project file. The
           default is to have Visual Studio invoke SCons with the -c option to remove any
           specified targets.

       MSVSENCODING
           The encoding string placed in a generated Microsoft Visual C++ project file. The
           default is encoding Windows-1252.

       MSVSPROJECTCOM
           The action used to generate Microsoft Visual C++ project files.

       MSVSPROJECTSUFFIX
           The suffix used for Microsoft Visual C++ project (DSP) files. The default value is
           .vcxproj when using Visual Studio 2010 and later, .vcproj when using Visual Studio
           versions between 2002 and 2008, and .dsp when using Visual Studio 6.0.

       MSVSREBUILDCOM
           The rebuild command line placed in a generated Microsoft Visual C++ project file. The
           default is to have Visual Studio invoke SCons with any specified rebuild targets.

       MSVSSCONS
           The SCons used in generated Microsoft Visual C++ project files. The default is the
           version of SCons being used to generate the project file.

       MSVSSCONSCOM
           The default SCons command used in generated Microsoft Visual C++ project files.

       MSVSSCONSCRIPT
           The sconscript file (that is, SConstruct or SConscript file) that will be invoked by
           Visual C++ project files (through the $MSVSSCONSCOM variable). The default is the same
           sconscript file that contains the call to MSVSProject to build the project file.

       MSVSSCONSFLAGS
           The SCons flags used in generated Microsoft Visual C++ project files.

       MSVSSOLUTIONCOM
           The action used to generate Microsoft Visual Studio solution files.

       MSVSSOLUTIONSUFFIX
           The suffix used for Microsoft Visual Studio solution (DSW) files. The default value is
           .sln when using Visual Studio version 7.x (.NET 2002) and later, and .dsw when using
           Visual Studio 6.0.

       MT
           The program used on Windows systems to embed manifests into DLLs and EXEs. See also
           $WINDOWS_EMBED_MANIFEST.

       MTEXECOM
           The Windows command line used to embed manifests into executables. See also
           $MTSHLIBCOM.

       MTFLAGS
           Flags passed to the $MT manifest embedding program (Windows only).

       MTSHLIBCOM
           The Windows command line used to embed manifests into shared libraries (DLLs). See
           also $MTEXECOM.

       MWCW_VERSION
           The version number of the MetroWerks CodeWarrior C compiler to be used.

       MWCW_VERSIONS
           A list of installed versions of the MetroWerks CodeWarrior C compiler on this system.

       NAME
           Specfies the name of the project to package.

           See the Package builder.

       NINJA_ALIAS_NAME
           The name of the alias target which will cause SCons to create the ninja build file,
           and then (optionally) run ninja. The default value is generate-ninja.

       NINJA_CMD_ARGS
           A string which will pass arguments through SCons to the ninja command when scons
           executes ninja. Has no effect if $NINJA_DISABLE_AUTO_RUN is set.

           This value can also be passed on the command line:

               scons NINJA_CMD_ARGS=-v
               or
               scons NINJA_CMD_ARGS="-v -j 3"

       NINJA_COMPDB_EXPAND
           Boolean value to instruct ninja to expand the command line arguments normally put into
           response files. If true, prevents unexpanded lines in the compilation database like
           “gcc @rsp_file” and instead yields expanded lines like “gcc -c -o myfile.o myfile.c
           -Ia -DXYZ”.

           Ninja's compdb tool added the -x flag in Ninja V1.9.0

       NINJA_DEPFILE_PARSE_FORMAT
           Determines the type of format ninja should expect when parsing header include
           depfiles. Can be msvc, gcc, or clang. The msvc option corresponds to /showIncludes
           format, and gcc or clang correspond to -MMD -MF.

       NINJA_DIR
           The builddir value. Propagates directly into the generated ninja build file. From
           Ninja's docs: “ A directory for some Ninja output files. ... (You can also store other
           build output in this directory.) ” The default value is .ninja.

       NINJA_DISABLE_AUTO_RUN
           Boolean. Default: False. If true, SCons will not run ninja automatically after
           creating the ninja build file.

           If not explicitly set, this will be set to True if --disable_execute_ninja or
           SetOption('disable_execute_ninja', True) is seen.

       NINJA_ENV_VAR_CACHE
           A string that sets the environment for any environment variables that differ between
           the OS environment and the SCons execution environment.

           It will be compatible with the default shell of the operating system.

           If not explicitly set, SCons will generate this dynamically from the execution
           environment stored in the current construction environment (e.g.  env['ENV']) where
           those values differ from the existing shell..

       NINJA_FILE_NAME
           The filename for the generated Ninja build file. The default is ninja.build.

       NINJA_FORCE_SCONS_BUILD
           If true, causes the build nodes to callback to scons instead of using ninja to build
           them. This is intended to be passed to the environment on the builder invocation. It
           is useful if you have a build node which does something which is not easily translated
           into ninja.

       NINJA_GENERATED_SOURCE_ALIAS_NAME
           A string matching the name of a user defined alias which represents a list of all
           generated sources. This will prevent the auto-detection of generated sources from
           $NINJA_GENERATED_SOURCE_SUFFIXES. Then all other source files will be made to depend
           on this in the ninja build file, forcing the generated sources to be built first.

       NINJA_GENERATED_SOURCE_SUFFIXES
           The list of source file suffixes which are generated by SCons build steps. All source
           files which match these suffixes will be added to the _generated_sources alias in the
           output ninja build file. Then all other source files will be made to depend on this in
           the ninja build file, forcing the generated sources to be built first.

       NINJA_MSVC_DEPS_PREFIX
           The msvc_deps_prefix string. Propagates directly into the generated ninja build file.
           From Ninja's docs: “defines the string which should be stripped from msvc's
           /showIncludes output”

       NINJA_POOL
           Set the ninja_pool for this or all targets in scope for this env var.

       NINJA_REGENERATE_DEPS
           A generator function used to create a ninja depfile which includes all the files which
           would require SCons to be invoked if they change. Or a list of said files.

       _NINJA_REGENERATE_DEPS_FUNC
           Internal value used to specify the function to call with argument env to generate the
           list of files which if changed would require the ninja build file to be regenerated.

       NINJA_SCONS_DAEMON_KEEP_ALIVE
           The number of seconds for the SCons deamon launched by ninja to stay alive. (Default:
           180000)

       NINJA_SCONS_DAEMON_PORT
           The TCP/IP port for the SCons daemon to listen on.  NOTE: You cannot use a port
           already being listened to on your build machine.  (Default: random number between
           10000,60000)

       NINJA_SYNTAX
           The path to a custom ninja_syntax.py file which is used in generation. The tool
           currently assumes you have ninja installed as a Python module and grabs the syntax
           file from that installation if $NINJA_SYNTAX is not explicitly set.

       no_import_lib
           When set to non-zero, suppresses creation of a corresponding Windows static import lib
           by the SharedLibrary builder when used with MinGW, Microsoft Visual Studio or
           Metrowerks. This also suppresses creation of an export (.exp) file when using
           Microsoft Visual Studio.

       OBJPREFIX
           The prefix used for (static) object file names.

       OBJSUFFIX
           The suffix used for (static) object file names.

       PACKAGEROOT
           Specifies the directory where all files in resulting archive will be placed if
           applicable. The default value is “$NAME-$VERSION”.

           See the Package builder.

       PACKAGETYPE
           Selects the package type to build when using the Package builder. May be a string or
           list of strings. See the docuentation for the builder for the currently supported
           types.

           $PACKAGETYPE may be overridden with the --package-type command line option.

           See the Package builder.

       PACKAGEVERSION
           The version of the package (not the underlying project). This is currently only used
           by the rpm packager and should reflect changes in the packaging, not the underlying
           project code itself.

           See the Package builder.

       PCH
           The Microsoft Visual C++ precompiled header that will be used when compiling object
           files. This variable is ignored by tools other than Microsoft Visual C++. When this
           variable is defined SCons will add options to the compiler command line to cause it to
           use the precompiled header, and will also set up the dependencies for the PCH file.
           Example:

               env['PCH'] = File('StdAfx.pch')

       PCHCOM
           The command line used by the PCH builder to generated a precompiled header.

       PCHCOMSTR
           The string displayed when generating a precompiled header. If this is not set, then
           $PCHCOM (the command line) is displayed.

       PCHPDBFLAGS
           A construction variable that, when expanded, adds the /yD flag to the command line
           only if the $PDB construction variable is set.

       PCHSTOP
           This variable specifies how much of a source file is precompiled. This variable is
           ignored by tools other than Microsoft Visual C++, or when the PCH variable is not
           being used. When this variable is define it must be a string that is the name of the
           header that is included at the end of the precompiled portion of the source files, or
           the empty string if the "#pragma hrdstop" construct is being used:

               env['PCHSTOP'] = 'StdAfx.h'

       PDB
           The Microsoft Visual C++ PDB file that will store debugging information for object
           files, shared libraries, and programs. This variable is ignored by tools other than
           Microsoft Visual C++. When this variable is defined SCons will add options to the
           compiler and linker command line to cause them to generate external debugging
           information, and will also set up the dependencies for the PDB file. Example:

               env['PDB'] = 'hello.pdb'

           The Visual C++ compiler switch that SCons uses by default to generate PDB information
           is /Z7. This works correctly with parallel (-j) builds because it embeds the debug
           information in the intermediate object files, as opposed to sharing a single PDB file
           between multiple object files. This is also the only way to get debug information
           embedded into a static library. Using the /Zi instead may yield improved link-time
           performance, although parallel builds will no longer work. You can generate PDB files
           with the /Zi switch by overriding the default $CCPDBFLAGS variable; see the entry for
           that variable for specific examples.

       PDFLATEX
           The pdflatex utility.

       PDFLATEXCOM
           The command line used to call the pdflatex utility.

       PDFLATEXCOMSTR
           The string displayed when calling the pdflatex utility. If this is not set, then
           $PDFLATEXCOM (the command line) is displayed.

               env = Environment(PDFLATEX;COMSTR = "Building $TARGET from LaTeX input $SOURCES")

       PDFLATEXFLAGS
           General options passed to the pdflatex utility.

       PDFPREFIX
           The prefix used for PDF file names.

       PDFSUFFIX
           The suffix used for PDF file names.

       PDFTEX
           The pdftex utility.

       PDFTEXCOM
           The command line used to call the pdftex utility.

       PDFTEXCOMSTR
           The string displayed when calling the pdftex utility. If this is not set, then
           $PDFTEXCOM (the command line) is displayed.

               env = Environment(PDFTEXCOMSTR = "Building $TARGET from TeX input $SOURCES")

       PDFTEXFLAGS
           General options passed to the pdftex utility.

       PKGCHK
           On Solaris systems, the package-checking program that will be used (along with
           $PKGINFO) to look for installed versions of the Sun PRO C++ compiler. The default is
           /usr/sbin/pgkchk.

       PKGINFO
           On Solaris systems, the package information program that will be used (along with
           $PKGCHK) to look for installed versions of the Sun PRO C++ compiler. The default is
           pkginfo.

       PLATFORM
           The name of the platform used to create this construction environment.  SCons sets
           this when initializing the platform, which by default is auto-detected (see the
           platform argument to Environment).

               env = Environment(tools=[])
               if env['PLATFORM'] == 'cygwin':
                   Tool('mingw')(env)
               else:
                   Tool('msvc')(env)

       POAUTOINIT
           The $POAUTOINIT variable, if set to True (on non-zero numeric value), let the msginit
           tool to automatically initialize missing PO files with msginit(1). This applies to
           both, POInit and POUpdate builders (and others that use any of them).

       POCREATE_ALIAS
           Common alias for all PO files created with POInit builder (default: 'po-create'). See
           msginit tool and POInit builder.

       POSUFFIX
           Suffix used for PO files (default: '.po') See msginit tool and POInit builder.

       POTDOMAIN
           The $POTDOMAIN defines default domain, used to generate POT filename as $POTDOMAIN.pot
           when no POT file name is provided by the user. This applies to POTUpdate, POInit and
           POUpdate builders (and builders, that use them, e.g.  Translate). Normally (if
           $POTDOMAIN is not defined), the builders use messages.pot as default POT file name.

       POTSUFFIX
           Suffix used for PO Template files (default: '.pot'). See xgettext tool and POTUpdate
           builder.

       POTUPDATE_ALIAS
           Name of the common phony target for all PO Templates created with POUpdate (default:
           'pot-update'). See xgettext tool and POTUpdate builder.

       POUPDATE_ALIAS
           Common alias for all PO files being defined with POUpdate builder (default:
           'po-update'). See msgmerge tool and POUpdate builder.

       PRINT_CMD_LINE_FUNC
           A Python function used to print the command lines as they are executed (assuming
           command printing is not disabled by the -q or -s options or their equivalents). The
           function must accept four arguments: s, target, source and env.  s is a string showing
           the command being executed, target, is the target being built (file node, list, or
           string name(s)), source, is the source(s) used (file node, list, or string name(s)),
           and env is the environment being used.

           The function must do the printing itself. The default implementation, used if this
           variable is not set or is None, is to just print the string, as in:

               def print_cmd_line(s, target, source, env):
                   sys.stdout.write(s + "\n")

           Here is an example of a more interesting function:

               def print_cmd_line(s, target, source, env):
                   sys.stdout.write(
                       "Building %s -> %s...\n"
                       % (
                           ' and '.join([str(x) for x in source]),
                           ' and '.join([str(x) for x in target]),
                       )
                   )

               env = Environment(PRINT_CMD_LINE_FUNC=print_cmd_line)
               env.Program('foo', ['foo.c', 'bar.c'])

           This prints:

               ...
               scons: Building targets ...
               Building bar.c -> bar.o...
               Building foo.c -> foo.o...
               Building foo.o and bar.o -> foo...
               scons: done building targets.

           Another example could be a function that logs the actual commands to a file.

       PROGEMITTER
           Contains the emitter specification for the Program builder. The manpage section
           "Builder Objects" contains general information on specifying emitters.

       PROGPREFIX
           The prefix used for executable file names.

       PROGSUFFIX
           The suffix used for executable file names.

       PSCOM
           The command line used to convert TeX DVI files into a PostScript file.

       PSCOMSTR
           The string displayed when a TeX DVI file is converted into a PostScript file. If this
           is not set, then $PSCOM (the command line) is displayed.

       PSPREFIX
           The prefix used for PostScript file names.

       PSSUFFIX
           The prefix used for PostScript file names.

       QT3_AUTOSCAN
           Turn off scanning for mocable files. Use the Moc Builder to explicitly specify files
           to run moc on.

           Changed in 4.5.0: renamed from QT_AUTOSCAN.

       QT3_BINPATH
           The path where the Qt binaries are installed. The default value is '$QT3DIR/bin'.

           Changed in 4.5.0: renamed from QT_BINPATH.

       QT3_CPPPATH
           The path where the Qt header files are installed. The default value is
           '$QT3DIR/include'. Note: If you set this variable to None, the tool won't change the
           $CPPPATH construction variable.

           Changed in 4.5.0: renamed from QT_CPPPATH.

       QT3_DEBUG
           Prints lots of debugging information while scanning for moc files.

           Changed in 4.5.0: renamed from QT_DEBUG.

       QT3_LIB
           Default value is 'qt'. You may want to set this to 'qt-mt'. Note: If you set this
           variable to None, the tool won't change the $LIBS variable.

           Changed in 4.5.0: renamed from QT_LIB.

       QT3_LIBPATH
           The path where the Qt libraries are installed. The default value is '$QT3DIR/lib'.
           Note: If you set this variable to None, the tool won't change the $LIBPATH
           construction variable.

           Changed in 4.5.0: renamed from QT_LIBPATH.

       QT3_MOC
           Default value is '$QT3_BINPATH/moc'.

       QT3_MOCCXXPREFIX
           Default value is ''. Prefix for moc output files when source is a C++ file.

       QT3_MOCCXXSUFFIX
           Default value is '.moc'. Suffix for moc output files when source is a C++ file.

           Changed in 4.5.0: renamed from QT_MOCCXXSUFFIX.

       QT3_MOCFROMCXXCOM
           Command to generate a moc file from a C++ file.

           Changed in 4.5.0: renamed from QT_MOCFROMCXXCOM.

       QT3_MOCFROMCXXCOMSTR
           The string displayed when generating a moc file from a C++ file. If this is not set,
           then $QT3_MOCFROMCXXCOM (the command line) is displayed.

           Changed in 4.5.0: renamed from QT_MOCFROMCXXCOMSTR.

       QT3_MOCFROMCXXFLAGS
           Default value is '-i'. These flags are passed to moc when moccing a C++ file.

           Changed in 4.5.0: renamed from QT_MOCFROMCXXFLAGS.

       QT3_MOCFROMHCOM
           Command to generate a moc file from a header.

           Changed in 4.5.0: renamed from QT_MOCFROMSHCOM.

       QT3_MOCFROMHCOMSTR
           The string displayed when generating a moc file from a C++ file. If this is not set,
           then $QT3_MOCFROMHCOM (the command line) is displayed.

           Changed in 4.5.0: renamed from QT_MOCFROMSHCOMSTR.

       QT3_MOCFROMHFLAGS
           Default value is ''. These flags are passed to moc when moccing a header file.

           Changed in 4.5.0: renamed from QT_MOCFROMSHFLAGS.

       QT3_MOCHPREFIX
           Default value is 'moc_'. Prefix for moc output files when source is a header.

           Changed in 4.5.0: renamed from QT_MOCHPREFIX.

       QT3_MOCHSUFFIX
           Default value is '$CXXFILESUFFIX'. Suffix for moc output files when source is a
           header.

           Changed in 4.5.0: renamed from QT_MOCHSUFFIX.

       QT3_UIC
           Default value is '$QT3_BINPATH/uic'.

           Changed in 4.5.0: renamed from QT_UIC.

       QT3_UICCOM
           Command to generate header files from .ui files.

           Changed in 4.5.0: renamed from QT_UICCOM.

       QT3_UICCOMSTR
           The string displayed when generating header files from .ui files. If this is not set,
           then $QT3_UICCOM (the command line) is displayed.

           Changed in 4.5.0: renamed from QT_UICCOMSTR.

       QT3_UICDECLFLAGS
           Default value is ''. These flags are passed to uic when creating a header file from a
           .ui file.

           Changed in 4.5.0: renamed from QT_UICDECLFLAGS.

       QT3_UICDECLPREFIX
           Default value is ''. Prefix for uic generated header files.

           Changed in 4.5.0: renamed from QT_UICDECLPREFIX.

       QT3_UICDECLSUFFIX
           Default value is '.h'. Suffix for uic generated header files.

           Changed in 4.5.0: renamed from QT_UICDECLSUFFIX.

       QT3_UICIMPLFLAGS
           Default value is ''. These flags are passed to uic when creating a C++ file from a .ui
           file.

           Changed in 4.5.0: renamed from QT_UICIMPFLAGS.

       QT3_UICIMPLPREFIX
           Default value is 'uic_'. Prefix for uic generated implementation files.

           Changed in 4.5.0: renamed from QT_UICIMPLPREFIX.

       QT3_UICIMPLSUFFIX
           Default value is '$CXXFILESUFFIX'. Suffix for uic generated implementation files.

           Changed in 4.5.0: renamed from QT_UICIMPLSUFFIX.

       QT3_UISUFFIX
           Default value is '.ui'. Suffix of designer input files.

           Changed in 4.5.0: renamed from QT_UISUFFIX.

       QT3DIR
           The path to the Qt installation to build against. If not already set, qt3 tool tries
           to obtain this from os.environ; if not found there, it tries to make a guess.

           Changed in 4.5.0: renamed from QTDIR.

       RANLIB
           The archive indexer.

       RANLIBCOM
           The command line used to index a static library archive.

       RANLIBCOMSTR
           The string displayed when a static library archive is indexed. If this is not set,
           then $RANLIBCOM (the command line) is displayed.

               env = Environment(RANLIBCOMSTR = "Indexing $TARGET")

       RANLIBFLAGS
           General options passed to the archive indexer.

       RC
           The resource compiler used to build a Microsoft Visual C++ resource file.

       RCCOM
           The command line used to build a Microsoft Visual C++ resource file.

       RCCOMSTR
           The string displayed when invoking the resource compiler to build a Microsoft Visual
           C++ resource file. If this is not set, then $RCCOM (the command line) is displayed.

       RCFLAGS
           The flags passed to the resource compiler by the RES builder.

       RCINCFLAGS
           An automatically-generated construction variable containing the command-line options
           for specifying directories to be searched by the resource compiler. The value of
           $RCINCFLAGS is created by respectively prepending and appending $RCINCPREFIX and
           $RCINCSUFFIX to the beginning and end of each directory in $CPPPATH.

       RCINCPREFIX
           The prefix (flag) used to specify an include directory on the resource compiler
           command line. This will be prepended to the beginning of each directory in the
           $CPPPATH construction variable when the $RCINCFLAGS variable is expanded.

       RCINCSUFFIX
           The suffix used to specify an include directory on the resource compiler command line.
           This will be appended to the end of each directory in the $CPPPATH construction
           variable when the $RCINCFLAGS variable is expanded.

       RDirs
           A function that converts a string into a list of Dir instances by searching the
           repositories.

       REGSVR
           The program used on Windows systems to register a newly-built DLL library whenever the
           SharedLibrary builder is passed a keyword argument of register=True.

       REGSVRCOM
           The command line used on Windows systems to register a newly-built DLL library
           whenever the SharedLibrary builder is passed a keyword argument of register=True.

       REGSVRCOMSTR
           The string displayed when registering a newly-built DLL file. If this is not set, then
           $REGSVRCOM (the command line) is displayed.

       REGSVRFLAGS
           Flags passed to the DLL registration program on Windows systems when a newly-built DLL
           library is registered. By default, this includes the /s that prevents dialog boxes
           from popping up and requiring user attention.

       RMIC
           The Java RMI stub compiler.

       RMICCOM
           The command line used to compile stub and skeleton class files from Java classes that
           contain RMI implementations. Any options specified in the $RMICFLAGS construction
           variable are included on this command line.

       RMICCOMSTR
           The string displayed when compiling stub and skeleton class files from Java classes
           that contain RMI implementations. If this is not set, then $RMICCOM (the command line)
           is displayed.

               env = Environment(
                   RMICCOMSTR="Generating stub/skeleton class files $TARGETS from $SOURCES"
               )

       RMICFLAGS
           General options passed to the Java RMI stub compiler.

       RPATH
           A list of paths to search for shared libraries when running programs. Currently only
           used in the GNU (gnulink), IRIX (sgilink) and Sun (sunlink) linkers. Ignored on
           platforms and toolchains that don't support it. Note that the paths added to RPATH are
           not transformed by scons in any way: if you want an absolute path, you must make it
           absolute yourself.

       _RPATH
           An automatically-generated construction variable containing the rpath flags to be used
           when linking a program with shared libraries. The value of $_RPATH is created by
           respectively prepending $RPATHPREFIX and appending $RPATHSUFFIX to the beginning and
           end of each directory in $RPATH.

       RPATHPREFIX
           The prefix used to specify a directory to be searched for shared libraries when
           running programs. This will be prepended to the beginning of each directory in the
           $RPATH construction variable when the $_RPATH variable is automatically generated.

       RPATHSUFFIX
           The suffix used to specify a directory to be searched for shared libraries when
           running programs. This will be appended to the end of each directory in the $RPATH
           construction variable when the $_RPATH variable is automatically generated.

       RPCGEN
           The RPC protocol compiler.

       RPCGENCLIENTFLAGS
           Options passed to the RPC protocol compiler when generating client side stubs. These
           are in addition to any flags specified in the $RPCGENFLAGS construction variable.

       RPCGENFLAGS
           General options passed to the RPC protocol compiler.

       RPCGENHEADERFLAGS
           Options passed to the RPC protocol compiler when generating a header file. These are
           in addition to any flags specified in the $RPCGENFLAGS construction variable.

       RPCGENSERVICEFLAGS
           Options passed to the RPC protocol compiler when generating server side stubs. These
           are in addition to any flags specified in the $RPCGENFLAGS construction variable.

       RPCGENXDRFLAGS
           Options passed to the RPC protocol compiler when generating XDR routines. These are in
           addition to any flags specified in the $RPCGENFLAGS construction variable.

       SCANNERS
           A list of the available implicit dependency scanners. New file scanners may be added
           by appending to this list, although the more flexible approach is to associate
           scanners with a specific Builder. See the manpage sections "Builder Objects" and
           "Scanner Objects" for more information.

       SCONS_HOME
           The (optional) path to the SCons library directory, initialized from the external
           environment. If set, this is used to construct a shorter and more efficient search
           path in the $MSVSSCONS command line executed from Microsoft Visual C++ project files.

       SHCC
           The C compiler used for generating shared-library objects. See also $CC for compiling
           to static objects.

       SHCCCOM
           The command line used to compile a C source file to a shared-library object file. Any
           options specified in the $SHCFLAGS, $SHCCFLAGS and $CPPFLAGS construction variables
           are included on this command line. See also $CCCOM for compiling to static objects.

       SHCCCOMSTR
           If set, the string displayed when a C source file is compiled to a shared object file.
           If not set, then $SHCCCOM (the command line) is displayed. See also $CCCOMSTR for
           compiling to static objects.

               env = Environment(SHCCCOMSTR = "Compiling shared object $TARGET")

       SHCCFLAGS
           Options that are passed to the C and C++ compilers to generate shared-library objects.
           See also $CCFLAGS for compiling to static objects.

       SHCFLAGS
           Options that are passed to the C compiler (only; not C++) to generate shared-library
           objects. See also $CFLAGS for compiling to static objects.

       SHCXX
           The C++ compiler used for generating shared-library objects. See also $CXX for
           compiling to static objects.

       SHCXXCOM
           The command line used to compile a C++ source file to a shared-library object file.
           Any options specified in the $SHCXXFLAGS and $CPPFLAGS construction variables are
           included on this command line. See also $CXXCOM for compiling to static objects.

       SHCXXCOMSTR
           If set, the string displayed when a C++ source file is compiled to a shared object
           file. If not set, then $SHCXXCOM (the command line) is displayed. See also $CXXCOMSTR
           for compiling to static objects.

               env = Environment(SHCXXCOMSTR = "Compiling shared object $TARGET")

       SHCXXFLAGS
           Options that are passed to the C++ compiler to generate shared-library objects. See
           also $CXXFLAGS for compiling to static objects.

       SHDC
           The name of the compiler to use when compiling D source destined to be in a shared
           objects. See also $DC for compiling to static objects.

       SHDCOM
           The command line to use when compiling code to be part of shared objects. See also
           $DCOM for compiling to static objects.

       SHDCOMSTR
           If set, the string displayed when a D source file is compiled to a (shared) object
           file. If not set, then $SHDCOM (the command line) is displayed. See also $DCOMSTR for
           compiling to static objects.

       SHDLIBVERSIONFLAGS
           Extra flags added to $SHDLINKCOM when building versioned SharedLibrary. These flags
           are only used when $SHLIBVERSION is set.

       SHDLINK
           The linker to use when creating shared objects for code bases include D sources. See
           also $DLINK for linking static objects.

       SHDLINKCOM
           The command line to use when generating shared objects. See also $DLINKCOM for linking
           static objects.

       SHDLINKFLAGS
           The list of flags to use when generating a shared object. See also $DLINKFLAGS for
           linking static objects.

       SHELL
           A string naming the shell program that will be passed to the $SPAWN function. See the
           $SPAWN construction variable for more information.

       SHELL_ENV_GENERATORS
           A hook allowing the execution environment to be modified prior to the actual execution
           of a command line from an action via the spawner function defined by $SPAWN. Allows
           substitution based on targets and sources, as well as values from the construction
           environment, adding extra environment variables, etc.

           The value must be a list (or other iterable) of functions which each generate or alter
           the execution environment dictionary. The first function will be passed a copy of the
           initial execution environment ($ENV in the current construction environment); the
           dictionary returned by that function is passed to the next, until the iterable is
           exhausted and the result returned for use by the command spawner. The original
           execution environment is not modified.

           Each function provided in $SHELL_ENV_GENERATORS must accept four arguments and return
           a dictionary: env is the construction environment for this action; target is the list
           of targets associated with this action; source is the list of sources associated with
           this action; and shell_env is the current dictionary after iterating any previous
           $SHELL_ENV_GENERATORS functions (this can be compared to the original execution
           environment, which is available as env['ENV'], to detect any changes).

           Example:

               def custom_shell_env(env, target, source, shell_env):
                   """customize shell_env if desired"""
                   if str(target[0]) == 'special_target':
                       shell_env['SPECIAL_VAR'] = env.subst('SOME_VAR', target=target, source=source)
                   return shell_env

               env["SHELL_ENV_GENERATORS"] = [custom_shell_env]

           Available since 4.4

       SHF03
           The Fortran 03 compiler used for generating shared-library objects. You should
           normally set the $SHFORTRAN variable, which specifies the default Fortran compiler for
           all Fortran versions. You only need to set $SHF03 if you need to use a specific
           compiler or compiler version for Fortran 03 files.

       SHF03COM
           The command line used to compile a Fortran 03 source file to a shared-library object
           file. You only need to set $SHF03COM if you need to use a specific command line for
           Fortran 03 files. You should normally set the $SHFORTRANCOM variable, which specifies
           the default command line for all Fortran versions.

       SHF03COMSTR
           If set, the string displayed when a Fortran 03 source file is compiled to a
           shared-library object file. If not set, then $SHF03COM or $SHFORTRANCOM (the command
           line) is displayed.

       SHF03FLAGS
           Options that are passed to the Fortran 03 compiler to generated shared-library
           objects. You only need to set $SHF03FLAGS if you need to define specific user options
           for Fortran 03 files. You should normally set the $FORTRANCOMMONFLAGS variable, which
           specifies the user-specified options passed to the default Fortran compiler for all
           Fortran versions.

       SHF03PPCOM
           The command line used to compile a Fortran 03 source file to a shared-library object
           file after first running the file through the C preprocessor. Any options specified in
           the $SHF03FLAGS and $CPPFLAGS construction variables are included on this command
           line. You only need to set $SHF03PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 03 files. You should normally set the $SHFORTRANPPCOM
           variable, which specifies the default C-preprocessor command line for all Fortran
           versions.

       SHF03PPCOMSTR
           If set, the string displayed when a Fortran 03 source file is compiled to a
           shared-library object file after first running the file through the C preprocessor. If
           not set, then $SHF03PPCOM or $SHFORTRANPPCOM (the command line) is displayed.

       SHF08
           The Fortran 08 compiler used for generating shared-library objects. You should
           normally set the $SHFORTRAN variable, which specifies the default Fortran compiler for
           all Fortran versions. You only need to set $SHF08 if you need to use a specific
           compiler or compiler version for Fortran 08 files.

       SHF08COM
           The command line used to compile a Fortran 08 source file to a shared-library object
           file. You only need to set $SHF08COM if you need to use a specific command line for
           Fortran 08 files. You should normally set the $SHFORTRANCOM variable, which specifies
           the default command line for all Fortran versions.

       SHF08COMSTR
           If set, the string displayed when a Fortran 08 source file is compiled to a
           shared-library object file. If not set, then $SHF08COM or $SHFORTRANCOM (the command
           line) is displayed.

       SHF08FLAGS
           Options that are passed to the Fortran 08 compiler to generated shared-library
           objects. You only need to set $SHF08FLAGS if you need to define specific user options
           for Fortran 08 files. You should normally set the $FORTRANCOMMONFLAGS variable, which
           specifies the user-specified options passed to the default Fortran compiler for all
           Fortran versions.

       SHF08PPCOM
           The command line used to compile a Fortran 08 source file to a shared-library object
           file after first running the file through the C preprocessor. Any options specified in
           the $SHF08FLAGS and $CPPFLAGS construction variables are included on this command
           line. You only need to set $SHF08PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 08 files. You should normally set the $SHFORTRANPPCOM
           variable, which specifies the default C-preprocessor command line for all Fortran
           versions.

       SHF08PPCOMSTR
           If set, the string displayed when a Fortran 08 source file is compiled to a
           shared-library object file after first running the file through the C preprocessor. If
           not set, then $SHF08PPCOM or $SHFORTRANPPCOM (the command line) is displayed.

       SHF77
           The Fortran 77 compiler used for generating shared-library objects. You should
           normally set the $SHFORTRAN variable, which specifies the default Fortran compiler for
           all Fortran versions. You only need to set $SHF77 if you need to use a specific
           compiler or compiler version for Fortran 77 files.

       SHF77COM
           The command line used to compile a Fortran 77 source file to a shared-library object
           file. You only need to set $SHF77COM if you need to use a specific command line for
           Fortran 77 files. You should normally set the $SHFORTRANCOM variable, which specifies
           the default command line for all Fortran versions.

       SHF77COMSTR
           If set, the string displayed when a Fortran 77 source file is compiled to a
           shared-library object file. If not set, then $SHF77COM or $SHFORTRANCOM (the command
           line) is displayed.

       SHF77FLAGS
           Options that are passed to the Fortran 77 compiler to generated shared-library
           objects. You only need to set $SHF77FLAGS if you need to define specific user options
           for Fortran 77 files. You should normally set the $FORTRANCOMMONFLAGS variable, which
           specifies the user-specified options passed to the default Fortran compiler for all
           Fortran versions.

       SHF77PPCOM
           The command line used to compile a Fortran 77 source file to a shared-library object
           file after first running the file through the C preprocessor. Any options specified in
           the $SHF77FLAGS and $CPPFLAGS construction variables are included on this command
           line. You only need to set $SHF77PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 77 files. You should normally set the $SHFORTRANPPCOM
           variable, which specifies the default C-preprocessor command line for all Fortran
           versions.

       SHF77PPCOMSTR
           If set, the string displayed when a Fortran 77 source file is compiled to a
           shared-library object file after first running the file through the C preprocessor. If
           not set, then $SHF77PPCOM or $SHFORTRANPPCOM (the command line) is displayed.

       SHF90
           The Fortran 90 compiler used for generating shared-library objects. You should
           normally set the $SHFORTRAN variable, which specifies the default Fortran compiler for
           all Fortran versions. You only need to set $SHF90 if you need to use a specific
           compiler or compiler version for Fortran 90 files.

       SHF90COM
           The command line used to compile a Fortran 90 source file to a shared-library object
           file. You only need to set $SHF90COM if you need to use a specific command line for
           Fortran 90 files. You should normally set the $SHFORTRANCOM variable, which specifies
           the default command line for all Fortran versions.

       SHF90COMSTR
           If set, the string displayed when a Fortran 90 source file is compiled to a
           shared-library object file. If not set, then $SHF90COM or $SHFORTRANCOM (the command
           line) is displayed.

       SHF90FLAGS
           Options that are passed to the Fortran 90 compiler to generated shared-library
           objects. You only need to set $SHF90FLAGS if you need to define specific user options
           for Fortran 90 files. You should normally set the $FORTRANCOMMONFLAGS variable, which
           specifies the user-specified options passed to the default Fortran compiler for all
           Fortran versions.

       SHF90PPCOM
           The command line used to compile a Fortran 90 source file to a shared-library object
           file after first running the file through the C preprocessor. Any options specified in
           the $SHF90FLAGS and $CPPFLAGS construction variables are included on this command
           line. You only need to set $SHF90PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 90 files. You should normally set the $SHFORTRANPPCOM
           variable, which specifies the default C-preprocessor command line for all Fortran
           versions.

       SHF90PPCOMSTR
           If set, the string displayed when a Fortran 90 source file is compiled to a
           shared-library object file after first running the file through the C preprocessor. If
           not set, then $SHF90PPCOM or $SHFORTRANPPCOM (the command line) is displayed.

       SHF95
           The Fortran 95 compiler used for generating shared-library objects. You should
           normally set the $SHFORTRAN variable, which specifies the default Fortran compiler for
           all Fortran versions. You only need to set $SHF95 if you need to use a specific
           compiler or compiler version for Fortran 95 files.

       SHF95COM
           The command line used to compile a Fortran 95 source file to a shared-library object
           file. You only need to set $SHF95COM if you need to use a specific command line for
           Fortran 95 files. You should normally set the $SHFORTRANCOM variable, which specifies
           the default command line for all Fortran versions.

       SHF95COMSTR
           If set, the string displayed when a Fortran 95 source file is compiled to a
           shared-library object file. If not set, then $SHF95COM or $SHFORTRANCOM (the command
           line) is displayed.

       SHF95FLAGS
           Options that are passed to the Fortran 95 compiler to generated shared-library
           objects. You only need to set $SHF95FLAGS if you need to define specific user options
           for Fortran 95 files. You should normally set the $FORTRANCOMMONFLAGS variable, which
           specifies the user-specified options passed to the default Fortran compiler for all
           Fortran versions.

       SHF95PPCOM
           The command line used to compile a Fortran 95 source file to a shared-library object
           file after first running the file through the C preprocessor. Any options specified in
           the $SHF95FLAGS and $CPPFLAGS construction variables are included on this command
           line. You only need to set $SHF95PPCOM if you need to use a specific C-preprocessor
           command line for Fortran 95 files. You should normally set the $SHFORTRANPPCOM
           variable, which specifies the default C-preprocessor command line for all Fortran
           versions.

       SHF95PPCOMSTR
           If set, the string displayed when a Fortran 95 source file is compiled to a
           shared-library object file after first running the file through the C preprocessor. If
           not set, then $SHF95PPCOM or $SHFORTRANPPCOM (the command line) is displayed.

       SHFORTRAN
           The default Fortran compiler used for generating shared-library objects.

       SHFORTRANCOM
           The command line used to compile a Fortran source file to a shared-library object
           file. By default, any options specified in the $SHFORTRANFLAGS, $_FORTRANMODFLAG, and
           $_FORTRANINCFLAGS construction variables are included on this command line. See also
           $FORTRANCOM.

       SHFORTRANCOMSTR
           If set, the string displayed when a Fortran source file is compiled to a
           shared-library object file. If not set, then $SHFORTRANCOM (the command line) is
           displayed.

       SHFORTRANFLAGS
           Options that are passed to the Fortran compiler to generate shared-library objects.

       SHFORTRANPPCOM
           The command line used to compile a Fortran source file to a shared-library object file
           after first running the file through the C preprocessor. By default, any options
           specified in the $SHFORTRANFLAGS, $CPPFLAGS, $_CPPDEFFLAGS, $_FORTRANMODFLAG, and
           $_FORTRANINCFLAGS construction variables are included on this command line. See also
           $SHFORTRANCOM.

       SHFORTRANPPCOMSTR
           If set, the string displayed when a Fortran source file is compiled to a
           shared-library object file after first running the file through the C preprocessor. If
           not set, then $SHFORTRANPPCOM (the command line) is displayed.

       SHLIBEMITTER
           Contains the emitter specification for the SharedLibrary builder. The manpage section
           "Builder Objects" contains general information on specifying emitters.

       SHLIBNOVERSIONSYMLINKS
           Instructs the SharedLibrary builder to not create symlinks for versioned shared
           libraries.

       SHLIBPREFIX
           The prefix used for shared library file names.

       _SHLIBSONAME
           A macro that automatically generates shared library's SONAME based on $TARGET,
           $SHLIBVERSION and $SHLIBSUFFIX. Used by SharedLibrary builder when the linker tool
           supports SONAME (e.g.  gnulink).

       SHLIBSUFFIX
           The suffix used for shared library file names.

       SHLIBVERSION
           When this construction variable is defined, a versioned shared library is created by
           the SharedLibrary builder. This activates the $_SHLIBVERSIONFLAGS and thus modifies
           the $SHLINKCOM as required, adds the version number to the library name, and creates
           the symlinks that are needed.  $SHLIBVERSION versions should exist as alpha-numeric,
           decimal-delimited values as defined by the regular expression "\w+[\.\w+]*". Example
           $SHLIBVERSION values include '1', '1.2.3', and '1.2.gitaa412c8b'.

       _SHLIBVERSIONFLAGS
           This macro automatically introduces extra flags to $SHLINKCOM when building versioned
           SharedLibrary (that is when $SHLIBVERSION is set).  _SHLIBVERSIONFLAGS usually adds
           $SHLIBVERSIONFLAGS and some extra dynamically generated options (such as
           -Wl,-soname=$_SHLIBSONAME. It is unused by "plain" (unversioned) shared libraries.

       SHLIBVERSIONFLAGS
           Extra flags added to $SHLINKCOM when building versioned SharedLibrary. These flags are
           only used when $SHLIBVERSION is set.

       SHLINK
           The linker for programs that use shared libraries. See also $LINK for linking static
           objects.

           On POSIX systems (those using the link tool), you should normally not change this
           value as it defaults to a "smart" linker tool which selects a compiler driver matching
           the type of source files in use. So for example, if you set $SHCXX to a specific
           compiler name, and are compiling C++ sources, the smartlink function will
           automatically select the same compiler for linking.

       SHLINKCOM
           The command line used to link programs using shared libraries. See also $LINKCOM for
           linking static objects.

       SHLINKCOMSTR
           The string displayed when programs using shared libraries are linked. If this is not
           set, then $SHLINKCOM (the command line) is displayed. See also $LINKCOMSTR for linking
           static objects.

               env = Environment(SHLINKCOMSTR = "Linking shared $TARGET")

       SHLINKFLAGS
           General user options passed to the linker for programs using shared libraries. Note
           that this variable should not contain -l (or similar) options for linking with the
           libraries listed in $LIBS, nor -L (or similar) include search path options that scons
           generates automatically from $LIBPATH. See $_LIBFLAGS above, for the variable that
           expands to library-link options, and $_LIBDIRFLAGS above, for the variable that
           expands to library search path options. See also $LINKFLAGS for linking static
           objects.

       SHOBJPREFIX
           The prefix used for shared object file names.

       SHOBJSUFFIX
           The suffix used for shared object file names.

       SONAME
           Variable used to hard-code SONAME for versioned shared library/loadable module.

               env.SharedLibrary('test', 'test.c', SHLIBVERSION='0.1.2', SONAME='libtest.so.2')

           The variable is used, for example, by gnulink linker tool.

       SOURCE
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       SOURCE_URL
           The URL (web address) of the location from which the project was retrieved. This is
           used to fill in the Source: field in the controlling information for Ipkg and RPM
           packages.

           See the Package builder.

       SOURCES
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       SOVERSION
           This will construct the SONAME using on the base library name (test in the example
           below) and use specified SOVERSION to create SONAME.

               env.SharedLibrary('test', 'test.c', SHLIBVERSION='0.1.2', SOVERSION='2')

           The variable is used, for example, by gnulink linker tool.

           In the example above SONAME would be libtest.so.2 which would be a symlink and point
           to libtest.so.0.1.2

       SPAWN
           A command interpreter function that will be called to execute command line strings.
           The function must accept five arguments:

               def spawn(shell, escape, cmd, args, env):

           shell is a string naming the shell program to use, escape is a function that can be
           called to escape shell special characters in the command line, cmd is the path to the
           command to be executed, args holds the arguments to the command and env is a
           dictionary of environment variables defining the execution environment in which the
           command should be executed.

       STATIC_AND_SHARED_OBJECTS_ARE_THE_SAME
           When this variable is true, static objects and shared objects are assumed to be the
           same; that is, SCons does not check for linking static objects into a shared library.

       SUBST_DICT
           The dictionary used by the Substfile or Textfile builders for substitution values. It
           can be anything acceptable to the dict() constructor, so in addition to a dictionary,
           lists of tuples are also acceptable.

       SUBSTFILEPREFIX
           The prefix used for Substfile file names, an empty string by default.

       SUBSTFILESUFFIX
           The suffix used for Substfile file names, an empty string by default.

       SUMMARY
           A short summary of what the project is about. This is used to fill in the Summary:
           field in the controlling information for Ipkg and RPM packages, and as the
           Description: field in MSI packages.

           See the Package builder.

       SWIG
           The name of the SWIG compiler to use.

       SWIGCFILESUFFIX
           The suffix that will be used for intermediate C source files generated by SWIG. The
           default value is '_wrap$CFILESUFFIX' - that is, the concatenation of the string _wrap
           and the current C suffix $CFILESUFFIX. By default, this value is used whenever the
           -c++ option is not specified as part of the $SWIGFLAGS construction variable.

       SWIGCOM
           The command line used to call SWIG.

       SWIGCOMSTR
           The string displayed when calling SWIG. If this is not set, then $SWIGCOM (the command
           line) is displayed.

       SWIGCXXFILESUFFIX
           The suffix that will be used for intermediate C++ source files generated by SWIG. The
           default value is '_wrap$CXXFILESUFFIX' - that is, the concatenation of the string
           _wrap and the current C++ suffix $CXXFILESUFFIX. By default, this value is used
           whenever the -c++ option is specified as part of the $SWIGFLAGS construction variable.

       SWIGDIRECTORSUFFIX
           The suffix that will be used for intermediate C++ header files generated by SWIG.
           These are only generated for C++ code when the SWIG 'directors' feature is turned on.
           The default value is _wrap.h.

       SWIGFLAGS
           General options passed to SWIG. This is where you should set the target language
           (-python, -perl5, -tcl, etc.) and whatever other options you want to specify to SWIG,
           such as the -c++ to generate C++ code instead of C Code.

       _SWIGINCFLAGS
           An automatically-generated construction variable containing the SWIG command-line
           options for specifying directories to be searched for included files. The value of
           $_SWIGINCFLAGS is created by respectively prepending and appending $SWIGINCPREFIX and
           $SWIGINCSUFFIX to the beginning and end of each directory in $SWIGPATH.

       SWIGINCPREFIX
           The prefix used to specify an include directory on the SWIG command line. This will be
           prepended to the beginning of each directory in the $SWIGPATH construction variable
           when the $_SWIGINCFLAGS variable is automatically generated.

       SWIGINCSUFFIX
           The suffix used to specify an include directory on the SWIG command line. This will be
           appended to the end of each directory in the $SWIGPATH construction variable when the
           $_SWIGINCFLAGS variable is automatically generated.

       SWIGOUTDIR
           Specifies the output directory in which SWIG should place generated language-specific
           files. This will be used by SCons to identify the files that will be generated by the
           SWIG call, and translated into the swig -outdir option on the command line.

       SWIGPATH
           The list of directories that SWIG will search for included files.  SCons' SWIG
           implicit dependency scanner will search these directories for include files. The
           default value is an empty list.

           Don't explicitly put include directory arguments in $SWIGFLAGS the result will be
           non-portable and the directories will not be searched by the dependency scanner. Note:
           directory names in $SWIGPATH will be looked-up relative to the SConscript directory
           when they are used in a command. To force scons to look-up a directory relative to the
           root of the source tree use a top-relative path (#):

               env = Environment(SWIGPATH='#/include')

           The directory look-up can also be forced using the Dir() function:

               include = Dir('include')
               env = Environment(SWIGPATH=include)

           The directory list will be added to command lines through the automatically-generated
           $_SWIGINCFLAGS construction variable, which is constructed by respectively prepending
           and appending the values of the $SWIGINCPREFIX and $SWIGINCSUFFIX construction
           variables to the beginning and end of each directory in $SWIGPATH. Any command lines
           you define that need the SWIGPATH directory list should include $_SWIGINCFLAGS:

               env = Environment(SWIGCOM="my_swig -o $TARGET $_SWIGINCFLAGS $SOURCES")

       SWIGVERSION
           The detected version string of the SWIG tool.

       TAR
           The tar archiver.

       TARCOM
           The command line used to call the tar archiver.

       TARCOMSTR
           The string displayed when archiving files using the tar archiver. If this is not set,
           then $TARCOM (the command line) is displayed.

               env = Environment(TARCOMSTR = "Archiving $TARGET")

       TARFLAGS
           General options passed to the tar archiver.

       TARGET
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       TARGET_ARCH
           The name of the hardware architecture that objects created using this construction
           environment should target. Can be set when creating a construction environment by
           passing as a keyword argument in the Environment call.

           On the win32 platform, if the Microsoft Visual C++ compiler is available, msvc tool
           setup is done using $HOST_ARCH and $TARGET_ARCH. If a value is not specified, will be
           set to the same value as $HOST_ARCH. Changing the value after the environment is
           initialized will not cause the tool to be reinitialized. Compiled objects will be in
           the target architecture if the compilation system supports generating for that target.
           The latest compiler which can fulfill the requirement will be selected, unless a
           different version is directed by the value of the $MSVC_VERSION construction variable.

           On the win32/msvc combination, valid target arch values are x86, arm, i386 for 32-bit
           targets and amd64, arm64, x86_64 and ia64 (Itanium) for 64-bit targets. For example,
           if you want to compile 64-bit binaries, you would set TARGET_ARCH='x86_64' when
           creating the construction environment. Note that not all target architectures are
           supported for all Visual Studio / MSVC versions. Check the relevant Microsoft
           documentation.

           $TARGET_ARCH is not currently used by other compilation tools, but the option is
           reserved to do so in future

       TARGET_OS
           The name of the operating system that objects created using this construction
           environment should target. Can be set when creating a construction environment by
           passing as a keyword argument in the Environment call;.

           $TARGET_OS is not currently used by SCons but the option is reserved to do so in
           future

       TARGETS
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       TARSUFFIX
           The suffix used for tar file names.

       TEMPFILE
           A callable object used to handle overly long command line strings, since operations
           which call out to a shell will fail if the line is longer than the shell can accept.
           This tends to particularly impact linking. The tempfile object stores the command line
           in a temporary file in the appropriate format, and returns an alternate command line
           so the invoked tool will make use of the contents of the temporary file. If you need
           to replace the default tempfile object, the callable should take into account the
           settings of $MAXLINELENGTH, $TEMPFILEPREFIX, $TEMPFILESUFFIX, $TEMPFILEARGJOIN,
           $TEMPFILEDIR and $TEMPFILEARGESCFUNC.

       TEMPFILEARGESCFUNC
           The default argument escape function is SCons.Subst.quote_spaces. If you need to apply
           extra operations on a command argument (to fix Windows slashes, normalize paths, etc.)
           before writing to the temporary file, you can set the $TEMPFILEARGESCFUNC variable to
           a custom function. Such a function takes a single string argument and returns a new
           string with any modifications applied. Example:

               import sys
               import re
               from SCons.Subst import quote_spaces

               WINPATHSEP_RE = re.compile(r"\\([^\"'\\]|$)")

               def tempfile_arg_esc_func(arg):
                   arg = quote_spaces(arg)
                   if sys.platform != "win32":
                       return arg
                   # GCC requires double Windows slashes, let's use UNIX separator
                   return WINPATHSEP_RE.sub(r"/\1", arg)

               env["TEMPFILEARGESCFUNC"] = tempfile_arg_esc_func

       TEMPFILEARGJOIN
           The string to use to join the arguments passed to $TEMPFILE when the command line
           exceeds the limit set by $MAXLINELENGTH. The default value is a space. However for
           MSVC, MSLINK the default is a line separator as defined by os.linesep. Note this value
           is used literally and not expanded by the subst logic.

       TEMPFILEDIR
           The directory to create the long-lines temporary file in.

       TEMPFILEPREFIX
           The prefix for the name of the temporary file used to store command lines exceeding
           $MAXLINELENGTH. The default prefix is '@', which works for the Microsoft and GNU
           toolchains on Windows. Set this appropriately for other toolchains, for example '-@'
           for the diab compiler or '-via' for ARM toolchain.

       TEMPFILESUFFIX
           The suffix for the name of the temporary file used to store command lines exceeding
           $MAXLINELENGTH. The suffix should include the dot ('.') if one is wanted as it will
           not be added automatically. The default is .lnk.

       TEX
           The TeX formatter and typesetter.

       TEXCOM
           The command line used to call the TeX formatter and typesetter.

       TEXCOMSTR
           The string displayed when calling the TeX formatter and typesetter. If this is not
           set, then $TEXCOM (the command line) is displayed.

               env = Environment(TEXCOMSTR = "Building $TARGET from TeX input $SOURCES")

       TEXFLAGS
           General options passed to the TeX formatter and typesetter.

       TEXINPUTS
           List of directories that the LaTeX program will search for include directories. The
           LaTeX implicit dependency scanner will search these directories for \include and
           \import files.

       TEXTFILEPREFIX
           The prefix used for Textfile file names, an empty string by default.

       TEXTFILESUFFIX
           The suffix used for Textfile file names; .txt by default.

       TOOLS
           A list of the names of the Tool specifications that are part of this construction
           environment.

       UNCHANGED_SOURCES
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       UNCHANGED_TARGETS
           A reserved variable name that may not be set or used in a construction environment.
           (See the manpage section "Variable Substitution" for more information).

       VENDOR
           The person or organization who supply the packaged software. This is used to fill in
           the Vendor: field in the controlling information for RPM packages, and the
           Manufacturer: field in the controlling information for MSI packages.

           See the Package builder.

       VERSION
           The version of the project, specified as a string.

           See the Package builder.

       VSWHERE
           Specify the location of vswhere.exe.

           The vswhere.exe executable is distributed with Microsoft Visual Studio and Build Tools
           since the 2017 edition, but is also available standalone. It provides full information
           about installations of 2017 and later editions. With the -legacy argument, vswhere.exe
           can detect installations of the 2010 through 2015 editions with limited data returned.
           If VSWHERE is set, SCons will use that location.

           Otherwise SCons will look in the following locations and set VSWHERE to the path of
           the first vswhere.exe located.

           •   %ProgramFiles(x86)%\Microsoft Visual Studio\Installer

           •   %ProgramFiles%\Microsoft Visual Studio\Installer

           •   %ChocolateyInstall%\bin

           Note that VSWHERE must be set at the same time or prior to any of msvc, msvs , and/or
           mslink Tool being initialized. Either set it as follows

               env = Environment(VSWHERE='c:/my/path/to/vswhere')

           or if your construction environment is created specifying an empty tools list (or a
           list of tools which omits all of default, msvs, msvc, and mslink), and also before
           env.Tool is called to ininitialize any of those tools:

                   env = Environment(tools=[])
                   env['VSWHERE'] = r'c:/my/vswhere/install/location/vswhere.exe'
                   env.Tool('msvc')
                   env.Tool('mslink')
                   env.Tool('msvs')

       WINDOWS_EMBED_MANIFEST
           Set to True to embed the compiler-generated manifest (normally ${TARGET}.manifest)
           into all Windows executables and DLLs built with this environment, as a resource
           during their link step. This is done using $MT and $MTEXECOM and $MTSHLIBCOM. See also
           $WINDOWS_INSERT_MANIFEST.

       WINDOWS_INSERT_DEF
           If set to true, a library build of a Windows shared library (.dll file) will include a
           reference to the corresponding module-definition file at the same time, if a
           module-definition file is not already listed as a build target. The name of the
           module-definition file will be constructed from the base name of the library and the
           construction variables $WINDOWSDEFSUFFIX and $WINDOWSDEFPREFIX. The default is to not
           add a module-definition file. The module-definition file is not created by this
           directive, and must be supplied by the developer.

       WINDOWS_INSERT_MANIFEST
           If set to true, scons will add the manifest file generated by Microsoft Visual C++ 8.0
           and later to the target list so SCons will be aware they were generated. In the case
           of an executable, the manifest file name is constructed using
           $WINDOWSPROGMANIFESTSUFFIX and $WINDOWSPROGMANIFESTPREFIX. In the case of a shared
           library, the manifest file name is constructed using $WINDOWSSHLIBMANIFESTSUFFIX and
           $WINDOWSSHLIBMANIFESTPREFIX. See also $WINDOWS_EMBED_MANIFEST.

       WINDOWSDEFPREFIX
           The prefix used for a Windows linker module-definition file name. Defaults to empty.

       WINDOWSDEFSUFFIX
           The suffix used for a Windows linker module-definition file name. Defaults to .def.

       WINDOWSEXPPREFIX
           The prefix used for Windows linker exports file names. Defaults to empty.

       WINDOWSEXPSUFFIX
           The suffix used for Windows linker exports file names. Defaults to .exp.

       WINDOWSPROGMANIFESTPREFIX
           The prefix used for executable program manifest files generated by Microsoft Visual
           C/C++. Defaults to empty.

       WINDOWSPROGMANIFESTSUFFIX
           The suffix used for executable program manifest files generated by Microsoft Visual
           C/C++. Defaults to .manifest.

       WINDOWSSHLIBMANIFESTPREFIX
           The prefix used for shared library manifest files generated by Microsoft Visual C/C++.
           Defaults to empty.

       WINDOWSSHLIBMANIFESTSUFFIX
           The suffix used for shared library manifest files generated by Microsoft Visual C/C++.
           Defaults to .manifest.

       X_IPK_DEPENDS
           This is used to fill in the Depends: field in the controlling information for Ipkg
           packages.

           See the Package builder.

       X_IPK_DESCRIPTION
           This is used to fill in the Description: field in the controlling information for Ipkg
           packages. The default value is “$SUMMARY\n$DESCRIPTION”

       X_IPK_MAINTAINER
           This is used to fill in the Maintainer: field in the controlling information for Ipkg
           packages.

       X_IPK_PRIORITY
           This is used to fill in the Priority: field in the controlling information for Ipkg
           packages.

       X_IPK_SECTION
           This is used to fill in the Section: field in the controlling information for Ipkg
           packages.

       X_MSI_LANGUAGE
           This is used to fill in the Language: attribute in the controlling information for MSI
           packages.

           See the Package builder.

       X_MSI_LICENSE_TEXT
           The text of the software license in RTF format. Carriage return characters will be
           replaced with the RTF equivalent \\par.

           See the Package builder.

       X_MSI_UPGRADE_CODE
           TODO

       X_RPM_AUTOREQPROV
           This is used to fill in the AutoReqProv: field in the RPM .spec file.

           See the Package builder.

       X_RPM_BUILD
           internal, but overridable

       X_RPM_BUILDREQUIRES
           This is used to fill in the BuildRequires: field in the RPM .spec file. Note this
           should only be used on a host managed by rpm as the dependencies will not be
           resolvable at build time otherwise.

       X_RPM_BUILDROOT
           internal, but overridable

       X_RPM_CLEAN
           internal, but overridable

       X_RPM_CONFLICTS
           This is used to fill in the Conflicts: field in the RPM .spec file.

       X_RPM_DEFATTR
           This value is used as the default attributes for the files in the RPM package. The
           default value is “(-,root,root)”.

       X_RPM_DISTRIBUTION
           This is used to fill in the Distribution: field in the RPM .spec file.

       X_RPM_EPOCH
           This is used to fill in the Epoch: field in the RPM .spec file.

       X_RPM_EXCLUDEARCH
           This is used to fill in the ExcludeArch: field in the RPM .spec file.

       X_RPM_EXLUSIVEARCH
           This is used to fill in the ExclusiveArch: field in the RPM .spec file.

       X_RPM_EXTRADEFS
           A list used to supply extra defintions or flags to be added to the RPM .spec file.
           Each item is added as-is with a carriage return appended. This is useful if some
           specific RPM feature not otherwise anticipated by SCons needs to be turned on or off.
           Note if this variable is omitted, SCons will by default supply the value '%global
           debug_package %{nil}' to disable debug package generation. To enable debug package
           generation, include this variable set either to None, or to a custom list that does
           not include the default line. Added in version 3.1.

               env.Package(
                   NAME="foo",
                   ...
                   X_RPM_EXTRADEFS=[
                       "%define _unpackaged_files_terminate_build 0"
                       "%define _missing_doc_files_terminate_build 0"
                   ],
                   ...
               )

       X_RPM_GROUP
           This is used to fill in the Group: field in the RPM .spec file.

       X_RPM_GROUP_lang
           This is used to fill in the Group(lang): field in the RPM .spec file. Note that lang
           is not literal and should be replaced by the appropriate language code.

       X_RPM_ICON
           This is used to fill in the Icon: field in the RPM .spec file.

       X_RPM_INSTALL
           internal, but overridable

       X_RPM_PACKAGER
           This is used to fill in the Packager: field in the RPM .spec file.

       X_RPM_POSTINSTALL
           This is used to fill in the %post: section in the RPM .spec file.

       X_RPM_POSTUNINSTALL
           This is used to fill in the %postun: section in the RPM .spec file.

       X_RPM_PREFIX
           This is used to fill in the Prefix: field in the RPM .spec file.

       X_RPM_PREINSTALL
           This is used to fill in the %pre: section in the RPM .spec file.

       X_RPM_PREP
           internal, but overridable

       X_RPM_PREUNINSTALL
           This is used to fill in the %preun: section in the RPM .spec file.

       X_RPM_PROVIDES
           This is used to fill in the Provides: field in the RPM .spec file.

       X_RPM_REQUIRES
           This is used to fill in the Requires: field in the RPM .spec file.

       X_RPM_SERIAL
           This is used to fill in the Serial: field in the RPM .spec file.

       X_RPM_URL
           This is used to fill in the Url: field in the RPM .spec file.

       XGETTEXT
           Path to xgettext(1) program (found via Detect()). See xgettext tool and POTUpdate
           builder.

       XGETTEXTCOM
           Complete xgettext command line. See xgettext tool and POTUpdate builder.

       XGETTEXTCOMSTR
           A string that is shown when xgettext(1) command is invoked (default: '', which means
           "print $XGETTEXTCOM"). See xgettext tool and POTUpdate builder.

       _XGETTEXTDOMAIN
           Internal "macro". Generates xgettext domain name form source and target (default:
           '${TARGET.filebase}').

       XGETTEXTFLAGS
           Additional flags to xgettext(1). See xgettext tool and POTUpdate builder.

       XGETTEXTFROM
           Name of file containing list of xgettext(1)'s source files. Autotools' users know this
           as POTFILES.in so they will in most cases set XGETTEXTFROM="POTFILES.in" here. The
           $XGETTEXTFROM files have same syntax and semantics as the well known GNU POTFILES.in.
           See xgettext tool and POTUpdate builder.

       _XGETTEXTFROMFLAGS
           Internal "macro". Genrates list of -D<dir> flags from the $XGETTEXTPATH list.

       XGETTEXTFROMPREFIX
           This flag is used to add single $XGETTEXTFROM file to xgettext(1)'s commandline
           (default: '-f').

       XGETTEXTFROMSUFFIX
           (default: '')

       XGETTEXTPATH
           List of directories, there xgettext(1) will look for source files (default: []).

               Note
               This variable works only together with $XGETTEXTFROM
           See also xgettext tool and POTUpdate builder.

       _XGETTEXTPATHFLAGS
           Internal "macro". Generates list of -f<file> flags from $XGETTEXTFROM.

       XGETTEXTPATHPREFIX
           This flag is used to add single search path to xgettext(1)'s commandline (default:
           '-D').

       XGETTEXTPATHSUFFIX
           (default: '')

       YACC
           The parser generator.

       YACC_GRAPH_FILE
           If supplied, write a graph of the automaton to a file with the name taken from this
           variable. Will be emitted as a --graph= command-line option. Use this in preference to
           including --graph= in $YACCFLAGS directly.

       YACC_HEADER_FILE
           If supplied, generate a header file with the name taken from this variable. Will be
           emitted as a --header= command-line option. Use this in preference to including
           --header= in $YACCFLAGS directly.

       YACCCOM
           The command line used to call the parser generator to generate a source file.

       YACCCOMSTR
           The string displayed when generating a source file using the parser generator. If this
           is not set, then $YACCCOM (the command line) is displayed.

               env = Environment(YACCCOMSTR="Yacc'ing $TARGET from $SOURCES")

       YACCFLAGS
           General options passed to the parser generator. In addition to passing the value on
           during invocation, the yacc tool also examines this construction variable for options
           which cause additional output files to be generated, and adds those to the target
           list.

           If a -d option is present, scons assumes that the call will also create a header file
           with the suffix defined by $YACCHFILESUFFIX if the yacc source file ends in a .y
           suffix, or a file with the suffix defined by $YACCHXXFILESUFFIX if the yacc source
           file ends in a .yy suffix.

           If a -g option is present, scons assumes that the call will also create a graph file
           with the suffix defined by $YACCVCGFILESUFFIX.

           If a -v option is present, scons assumes that the call will also create an output
           debug file with the suffix .output.

           Also recognized are GNU bison options --header= and its deprecated synonym --defines=,
           which is similar to -d but the output filename is named by the option argument; and
           --graph=, which is similar to -g but the output filename is named by the option
           argument.

           Note that files specified by --header= and --graph= may not be properly handled by
           SCons in all situations. Consider using $YACC_HEADER_FILE and $YACC_GRAPH_FILE
           instead.

       YACCHFILESUFFIX
           The suffix of the C header file generated by the parser generator when the -d option
           is used. Note that setting this variable does not cause the parser generator to
           generate a header file with the specified suffix, it exists to allow you to specify
           what suffix the parser generator will use of its own accord. The default value is .h.

       YACCHXXFILESUFFIX
           The suffix of the C++ header file generated by the parser generator when the -d option
           is used. Note that setting this variable does not cause the parser generator to
           generate a header file with the specified suffix, it exists to allow you to specify
           what suffix the parser generator will use of its own accord. The default value is
           .hpp, except on Mac OS X, where the default is ${TARGET.suffix}.h. because the default
           bison parser generator just appends .h to the name of the generated C++ file.

       YACCVCGFILESUFFIX
           The suffix of the file containing the VCG grammar automaton definition when the
           --graph= option is used. Note that setting this variable does not cause the parser
           generator to generate a VCG file with the specified suffix, it exists to allow you to
           specify what suffix the parser generator will use of its own accord. The default value
           is .vcg.

       ZIP
           The zip compression and file packaging utility.

       ZIP_OVERRIDE_TIMESTAMP
           An optional timestamp which overrides the last modification time of the file when
           stored inside the Zip archive. This is a tuple of six values: Year (>= 1980) Month
           (one-based) Day of month (one-based) Hours (zero-based) Minutes (zero-based) Seconds
           (zero-based)

       ZIPCOM
           The command line used to call the zip utility, or the internal Python function used to
           create a zip archive.

       ZIPCOMPRESSION
           The compression flag from the Python zipfile module used by the internal Python
           function to control whether the zip archive is compressed or not. The default value is
           zipfile.ZIP_DEFLATED, which creates a compressed zip archive. This value has no effect
           if the zipfile module is unavailable.

       ZIPCOMSTR
           The string displayed when archiving files using the zip utility. If this is not set,
           then $ZIPCOM (the command line or internal Python function) is displayed.

               env = Environment(ZIPCOMSTR = "Zipping $TARGET")

       ZIPFLAGS
           General options passed to the zip utility.

       ZIPROOT
           An optional zip root directory (default empty). The filenames stored in the zip file
           will be relative to this directory, if given. Otherwise the filenames are relative to
           the current directory of the command. For instance:

               env = Environment()
               env.Zip('foo.zip', 'subdir1/subdir2/file1', ZIPROOT='subdir1')

           will produce a zip file foo.zip containing a file with the name subdir2/file1 rather
           than subdir1/subdir2/file1.

       ZIPSUFFIX
           The suffix used for zip file names.

   Configure Contexts
       SCons supports a configure context, an integrated mechanism similar to the various
       AC_CHECK macros in GNU Autoconf for testing the existence of external items needed for the
       build, such as C header files, libraries, etc. The mechanism is portable across platforms.

       scons does not maintain an explicit cache of the tested values (this is different than
       Autoconf), but uses its normal dependency tracking to keep the checked values up to date.
       However, users may override this behaviour with the --config command line option.

       Configure(env, [custom_tests, conf_dir, log_file, config_h, clean, help]),
       env.Configure([custom_tests, conf_dir, log_file, config_h, clean, help])
           Create a configure context, which tracks information discovered while running tests.
           The context includes a local construction environment (available as context.env) which
           is used when running the tests and which can be updated with the check results. Only
           one context may be active at a time, but a new context can be created after the active
           one is completed. For the global function form, the required env describes the initial
           values for the context's local construction environment; for the construction
           environment method form the instance provides the values.

           Changed in version 4.0: raises an exception on an attempt to create a new context when
           there is an active context.

           custom_tests specifies a dictionary containing custom tests (see the section on custom
           tests below). The default value is None, meaning no custom tests are added to the
           configure context.

           conf_dir specifies a directory where the test cases are built. This directory is not
           used for building normal targets. The default value is “#/.sconf_temp”.

           log_file specifies a file which collects the output from commands that are executed to
           check for the existence of header files, libraries, etc. The default is
           “#/config.log”. If you are using variant directories, you may want to place the log
           file for a given build under that build's variant directory.

           config_h specifies a C header file where the results of tests will be written. The
           results will consist of lines like #define HAVE_STDIO_H, #define HAVE_LIBM, etc.
           Customarily, the name chosen is “config.h”. The default is to not write a config_h
           file. You can specify the same config_h file in multiple calls to Configure, in which
           case SCons will concatenate all results in the specified file. Note that SCons uses
           its normal dependency checking to decide if it's necessary to rebuild the specified
           config_h file. This means that the file is not necessarily re-built each time scons is
           run, but is only rebuilt if its contents will have changed and some target that
           depends on the config_h file is being built.

           The clean and help arguments can be used to suppress execution of the configuration
           tests when the -c/--clean or -H/-h/--help options are used, respectively. The default
           behavior is always to execute configure context tests, since the results of the tests
           may affect the list of targets to be cleaned or the help text. If the configure tests
           do not affect these, then you may add the clean=False or help=False arguments (or
           both) to avoid unnecessary test execution.

       context.Finish()
           This method must be called after configuration is done. Though required, this is not
           enforced except if Configure is called again while there is still an active context,
           in which case an exception is raised.  Finish returns the environment as modified
           during the course of running the configuration checks. After this method is called, no
           further checks can be performed with this configuration context. However, you can
           create a new configure context to perform additional checks.

       Example of a typical Configure usage:

           env = Environment()
           conf = Configure(env)
           if not conf.CheckCHeader("math.h"):
               print("We really need math.h!")
               Exit(1)
           if conf.CheckLibWithHeader("qt", "qapp.h", "c++", "QApplication qapp(0,0);"):
               # do stuff for qt - usage, e.g.
               conf.env.Append(CPPDEFINES="WITH_QT")
           env = conf.Finish()

       A configure context has the following predefined methods which can be used to perform
       checks. Where language is an optional parameter, it specifies the compiler to use for the
       check, currently a choice of C or C++. The spellings accepted for C are “C” or “c”; for
       C++ the value can be “CXX”, “cxx”, “C++” or “c++”. If language is omitted, “C” is assumed.

       context.CheckHeader(header, [include_quotes, language])
           Checks if header is usable in the specified language.  header may be a list, in which
           case the last item in the list is the header file to be checked, and the previous list
           items are header files whose #include lines should precede the header line being
           checked for. The optional argument include_quotes must be a two character string,
           where the first character denotes the opening quote and the second character denotes
           the closing quote. By default, both characters are " (double quote).

           Returns a boolean indicating success or failure.

       context.CheckCHeader(header, [include_quotes])
           Checks if header is usable when compiling a C language program.  header may be a list,
           in which case the last item in the list is the header file to be checked, and the
           previous list items are header files whose #include lines should precede the header
           line being checked for. The optional argument include_quotes must be a two character
           string, where the first character denotes the opening quote and the second character
           denotes the closing quote. By default, both characters are " (double quote). Note this
           is a wrapper around CheckHeader. Returns a boolean indicating success or failure.

       context.CheckCXXHeader(header, [include_quotes])
           Checks if header is usable when compiling a C++ language program.  header may be a
           list, in which case the last item in the list is the header file to be checked, and
           the previous list items are header files whose #include lines should precede the
           header line being checked for. The optional argument include_quotes must be a two
           character string, where the first character denotes the opening quote and the second
           character denotes the closing quote. By default, both characters are " (double quote).
           Note this is a wrapper around CheckHeader. Returns a boolean indicating success or
           failure.

       context.CheckFunc(function_name, [header, language])
           Checks if function_name is usable in the context's local environment, using the
           compiler specified by language - that is, can a check referencing it be compiled using
           the current values of $CFLAGS, $CPPFLAGS, $LIBS or other relevant construction
           variables.

           The optional header argument is a string representing a code fragment to place at the
           top of the test program that will be compiled to check if the function exists. If
           omitted, the default stanza will be (with function_name appropriately substituted):

               #ifdef __cplusplus
               extern "C"
               #endif
               char function_name(void);

           Note: if header is supplied, it should not include the standard header file that
           declares function_name, and it should include a dummy prototype similar to the default
           case. Compilers reject builds where a function call does not match the declared
           prototype as happens if the "real" header is included, and modern compilers are now
           rejecting implicit function declarations.

           Returns a boolean indicating success or failure.

       context.CheckLib([library, symbol, header, language, autoadd=True, append=True,
       unique=False])
           Checks if library provides symbol by compiling a simple stub program with the compiler
           selected by language, and optionally adds that library to the context. If supplied,
           the text of header is included at the top of the stub. If autoadd is true (the
           default), and the library provides the specified symbol (as defined by successfully
           linking the stub program), it is added to the $LIBS construction variable in the
           context. if append is true (the default), the library is appended, otherwise it is
           prepended. If unique is true, and the library would otherwise be added but is already
           present in $LIBS in the configure context, it will not be added again. The default is
           False.

           library can be a list of library names, or None (the default if the argument is
           omitted). If the former, symbol is checked against each library name in order,
           returning (and reporting success) on the first successful test; if the latter, it is
           checked with the current value of $LIBS (in this case no library name would be added).
           If symbol is omitted or None, then CheckLib just checks if you can link against the
           specified library, Note though it is legal syntax, it would not be very useful to call
           this method with library and symbol both omitted or None - at least one should be
           supplied.

           Returns a boolean indicating success or failure.

           Changed in version 4.5.0: added the append and unique parameters.

       context.CheckLibWithHeader(library, header, [language, call, autoadd=True, append=True,
       unique=False])
           Provides an alternative to the CheckLib method for checking for libraries usable in a
           build.  library specifies a library or list of libraries to check.  header specifies a
           header to include in the test program, and language indicates the compiler to use.
           header may be a list, in which case the last item in the list is the header file to be
           checked, and the previous list items are header files whose #include lines should
           precede the header line being checked for. A code fragment (must be a a valid
           expression, including a trailing semicolon) to serve as the test can be supplied in
           call; if not supplied, the default checks the ability to link against the specified
           library. If autoadd is true (the default), the first library that passes the check is
           added to the $LIBS construction variable in the context and the method returns. If
           append is true (the default), the library is appended, otherwise prepended. If unique
           is true, and the library would otherwise be added but is already present in $LIBS in
           the configure context, it will not be added again. The default is False.

           Returns a boolean indicating success or failure.

           Changed in version 4.5.0: added the append and unique parameters.

       context.CheckType(type_name, [includes, language])
           Checks for the existence of a type defined by typedef.  type_name specifies the
           typedef name to check for.  includes is a string containing one or more #include lines
           that will be inserted into the program that will be run to test for the existence of
           the type. Example:

               sconf.CheckType('foo_type', '#include "my_types.h"', 'C++')

           Returns a boolean indicating success or failure.

       context.CheckTypeSize(type_name, [header, language, expect])
           Checks for the size of a type defined by typedef.  type_name specifies the typedef
           name to check for. The optional header argument is a string that will be placed at the
           top of the test file that will be compiled to check if the type exists; the default is
           empty. If the optional expect, is supplied, it should be an integer size;
           CheckTypeSize will fail unless type_name is actually that size. Returns the size in
           bytes, or zero if the type was not found (or if the size did not match optional
           expect).

           For example,

               CheckTypeSize('short', expect=2)

           will return the size 2 only if short is actually two bytes.

       context.CheckCC()
           Checks whether the C compiler (as defined by the $CC construction variable) works, by
           trying to compile a small source file. This provides a more rigorous check: by
           default, SCons itself only detects if there is a program with the correct name, not if
           it is a functioning compiler. Returns a boolean indicating success or failure.

           The test program will be built with the same command line as the one used by the
           Object builder for C source files, so by setting relevant construction variables it
           can be used to detect if particular compiler flags will be accepted or rejected by the
           compiler.

           Returns a boolean indicating success or failure.

       context.CheckCXX()
           Checks whether the C++ compiler (as defined by the $CXX construction variable) works,
           by trying to compile a small source file. This provides a more rigorous check: by
           default, SCons itself only detects if there is a program with the correct name, not if
           it is a functioning compiler. Returns a boolean indicating success or failure.

           The test program will be built with the same command line as the one used by the
           Object builder for C++ source files, so by setting relevant construction variables it
           can be used to detect if particular compiler flags will be accepted or rejected by the
           compiler.

           Returns a boolean indicating success or failure.

       context.CheckSHCC()
           Checks whether the shared-object C compiler (as defined by the $SHCC construction
           variable) works by trying to compile a small source file. This provides a more
           rigorous check: by default, SCons itself only detects if there is a program with the
           correct name, not if it is a functioning compiler. Returns a boolean indicating
           success or failure.

           The test program will be built with the same command line as the one used by the
           SharedObject builder for C source files, so by setting relevant construction variables
           it can be used to detect if particular compiler flags will be accepted or rejected by
           the compiler. Note this does not check whether a shared library/dll can be created.

           Returns a boolean indicating success or failure.

       context.CheckSHCXX()
           Checks whether the shared-object C++ compiler (as defined by the $SHCXX construction
           variable) works by trying to compile a small source file. This provides a more
           rigorous check: by default, SCons itself only detects if there is a program with the
           correct name, not if it is a functioning compiler. Returns a boolean indicating
           success or failure.

           The test program will be built with the same command line as the one used by the
           SharedObject builder for C++ source files, so by setting relevant construction
           variables it can be used to detect if particular compiler flags will be accepted or
           rejected by the compiler. Note this does not check whether a shared library/dll can be
           created.

           Returns a boolean indicating success or failure.

       context.CheckProg(prog_name)
           Checks if prog_name exists in the path SCons will use at build time.
           (context.env['ENV']['PATH']). Returns a string containing the path to the program, or
           None on failure.

       context.CheckDeclaration(symbol, [includes, language])
           Checks if the specified symbol is declared.  includes is a string containing one or
           more #include lines that will be inserted into the program that will be run to test
           for the existence of the symbol.

           Returns a boolean indicating success or failure.

       context.CheckMember(aggregate_member, [header, language])
           Checks for the existence of a member of the C/C++ struct or class.  aggregate_member
           specifies the struct/class and member to check for.  header is a string containing one
           or more #include lines that will be inserted into the program that will be run to test
           for the existence of the member. Example:

               sconf.CheckMember('struct tm.tm_sec', '#include <time.h>')

           Returns a boolean indicating success or failure.

       context.Define(symbol, [value, comment])
           This method does not check for anything, but rather forces the definition of a
           preprocessor macro that will be added to the configuration header file.  name is the
           macro's identifier. If value is given, it will be be used as the macro replacement
           value. If value is a string and needs to display with quotes, the quotes need to be
           included, as in '"string"' If the optional comment is given, it is inserted as a
           comment above the macro definition (suitable comment marks will be added
           automatically). This is analogous to using AC_DEFINE in Autoconf.

           Examples:

               env = Environment()
               conf = Configure(env)

               # Puts the following line in the config header file:
               #    #define A_SYMBOL
               conf.Define("A_SYMBOL")

               # Puts the following line in the config header file:
               #    #define A_SYMBOL 1
               conf.Define("A_SYMBOL", 1)

           Examples of quoting string values:

               env = Environment()
               conf = Configure(env)

               # Puts the following line in the config header file:
               #    #define A_SYMBOL YA
               conf.Define("A_SYMBOL", "YA")

               # Puts the following line in the config header file:
               #    #define A_SYMBOL "YA"
               conf.Define("A_SYMBOL", '"YA"')

           Example including comment:

               env = Environment()
               conf = Configure(env)

               # Puts the following lines in the config header file:
               #    /* Set to 1 if you have a symbol */
               #    #define A_SYMBOL 1
               conf.Define("A_SYMBOL", 1, "Set to 1 if you have a symbol")

       You can define your own custom checks in addition to using the predefined checks. To
       enable custom checks, pass a dictionary to the Configure function as the custom_tests
       parameter. The dictionary maps the names of the checks to the custom check callables
       (either a Python function or an instance of a class implementing a __call__ method). Each
       custom check will be called with a a CheckContext instance as the first parameter followed
       by the remaining arguments, which must be supplied by the user of the check. A
       CheckContext is not the same as a configure context; rather it is an instance of a class
       which contains a configure context (available as chk_ctx.sconf). A CheckContext provides
       the following methods which custom checks can make use of::

       chk_ctx.Message(text)
           Displays text as an indicator of progess. For example: Checking for library X....
           Usually called before the check is started.

       chk_ctx.Result(res)
           Displays a result message as an indicator of progress. If res is an integer, displays
           yes if res evaluates true or no if false. If res is a string, it is displayed as-is.
           Usually called after the check has completed.

       chk_ctx.TryCompile(text, extension='')
           Checks if a file containing text and given the specified extension (e.g.  '.c') can be
           compiled to an object file using the environment's Object builder. Returns a boolean
           indicating success or failure.

       chk_ctx.TryLink(text, extension='')
           Checks if a file containing text and given the specified extension (e.g.  '.c') can be
           compiled to an executable program using the environment's Program builder. Returns a
           boolean indicating success or failure.

       chk_ctx.TryRun(text, extension='')
           Checks if a file containing text and given the specified extension (e.g.  '.c') can be
           compiled to an excutable program using the environment's Program builder and
           subsequently executed. Execution is only attempted if the build succeeds. If the
           program executes successfully (that is, its return status is 0), a tuple (True,
           outputStr) is returned, where outputStr is the standard output of the program. If the
           program fails execution (its return status is non-zero), then (False, '') is returned.

       chk_ctx.TryAction(action, [text, extension=''])
           Checks if the specified action with an optional source file (contents text, given
           extension extension) can be executed.  action may be anything which can be converted
           to an Action Object. On success, a tuple (True, outputStr) is returned, where
           outputStr is the content of the target file. On failure (False, '') is returned.

       chk_ctx.TryBuild(builder, [text, extension=''])
           Low level implementation for testing specific builds; the methods above are based on
           this method. Given the Builder instance builder and the optional text of a source file
           with optional extension, returns a boolean indicating success or failure. In addition,
           chk_ctx.lastTarget is set to the build target node if the build was successful.

       Example of implementing and using custom tests:

           def CheckQt(chk_ctx, qtdir):
               chk_ctx.Message('Checking for qt ...')
               lastLIBS = chk_ctx.env['LIBS']
               lastLIBPATH = chk_ctx.env['LIBPATH']
               lastCPPPATH = chk_ctx.env['CPPPATH']
               chk_ctx.env.Append(LIBS='qt', LIBPATH=qtdir + '/lib', CPPPATH=qtdir + '/include')
               ret = chk_ctx.TryLink(
                   """\
           #include <qapp.h>
           int main(int argc, char **argv) {
             QApplication qapp(argc, argv);
             return 0;
           }
           """
               )
               if not ret:
                   chkctx.env.Replace(LIBS=lastLIBS, LIBPATH=lastLIBPATH, CPPPATH=lastCPPPATH)
               chkctx.Result(ret)
               return ret

           env = Environment()
           conf = Configure(env, custom_tests={'CheckQt': CheckQt})
           if not conf.CheckQt('/usr/lib/qt'):
               print('We really need qt!')
               Exit(1)
           env = conf.Finish()

   Command-Line Construction Variables
       Often when building software, some variables need to be specified at build time. For
       example, libraries needed for the build may be in non-standard locations, or site-specific
       compiler options may need to be passed to the compiler.  SCons provides a Variables object
       to support overriding construction variables with values obtained from various sources,
       often from the command line:

           scons VARIABLE=foo

       The variable values can also be specified in a configuration file or an SConscript file.

       To obtain the object for manipulating values, call the Variables function:

       Variables([files, [args]])
           If files is a file or list of files, they are executed as Python scripts, and the
           values of (global) Python variables set in those files are added as construction
           variables in the Default Environment. If no files are specified, or the files argument
           is None, then no files will be read (supplying None is necessary if there are no files
           but you want to specify args as a positional argument).

           The following example file contents could be used to set an alternative C compiler:

               CC = 'my_cc'

           If args is specified, it is a dictionary of values that will override anything read
           from files. The primary use is to pass the ARGUMENTS dictionary that holds variables
           specified on the command line, allowing you to indicate that if a setting appears on
           both the command line and in the file(s), the command line setting takes precedence.
           However, any dictionary can be passed. Examples:

               vars = Variables('custom.py')
               vars = Variables('overrides.py', ARGUMENTS)
               vars = Variables(None, {FOO:'expansion', BAR:7})

           Calling Variables with no arguments is equivalent to:

               vars = Variables(files=None, args=ARGUMENTS)

           Note that since the variables are eventually added as construction variables, you
           should choose variable names which do not unintentionally change pre-defined
           construction variables that your project will make use of (see the section called
           “Construction Variables”).

       Variables objects have the following methods:

       vars.Add(key, [help, default, validator, converter])
           Add a customizable construction variable to the Variables object.  key is either the
           name of the variable, or a tuple (or list), in which case the first item in the tuple
           is taken as the variable name, and any remaining values are considered aliases for the
           variable.  help is the help text for the variable (default empty string).  default is
           the default value of the variable (default None). If default is None and a value is
           not specified, the construction variable will not be added to the construction
           environment.

           As a special case, if key is a tuple (or list) and is the only argument, the tuple is
           unpacked into the five parameters listed above left to right, with any missing members
           filled with the respecitive default values. This form allows Add to consume a tuple
           emitted by the convenience functions BoolVariable, EnumVariable, ListVariable,
           PackageVariable and PathVariable.

           If the optional validator is supplied, it is called to validate the value of the
           variable. A function supplied as a validator must accept three arguments: key, value
           and env, and should raise an exception with a helpful error message if value is
           invalid. No return value is expected from the validator.

           If the optional converter is supplied, it is called to convert the value before
           putting it in the environment, and should take either a value or a value and
           environment as parameters. The converter function must return a value, which will be
           converted into a string and be passed to the validator (if any) and then added to the
           construction environment.

           Examples:

               vars.Add('CC', help='The C compiler')

               def valid_color(key, val, env):
                   if not val in ['red', 'blue', 'yellow']:
                       raise Exception("Invalid color value '%s'" % val)

               vars.Add('COLOR', validator=valid_color)

       vars.AddVariables(args)
           A convenience method that adds one or more customizable construction variables to a
           Variables object in one call; equivalent to calling Add multiple times. The args are
           tuples (or lists) that contain the arguments for an individual call to the Add method.
           Since tuples are not Python mappings, the arguments cannot use the keyword form, but
           rather are positional arguments as documented for Add: a required name, the other four
           optional, but must be in the specified order if used.

               opt.AddVariables(
                   ("debug", "", 0),
                   ("CC", "The C compiler"),
                   ("VALIDATE", "An option for testing validation", "notset", validator, None),
               )

       vars.Update(env, [args])
           Update a construction environment env with the customized construction variables. Any
           specified variables that are not configured for the Variables object will be saved and
           may be retrieved using the UnknownVariables method.

           Normally this method is not called directly, but rather invoked indirectly by passing
           the Variables object to the Environment function:

               env = Environment(variables=vars)

       vars.UnknownVariables()
           Returns a dictionary containing any variables that were specified either in the files
           or the dictionary with which the Variables object was initialized, but for which the
           Variables object was not configured.

               env = Environment(variables=vars)
               for key, value in vars.UnknownVariables():
                   print("unknown variable:  %s=%s" % (key, value))

       vars.Save(filename, env)
           Save the currently set variables into a script file named by filename. Only variables
           that are set to non-default values are saved. You can load these saved settings on a
           subsequent run by passing filename to the Variables function, providing a way to cache
           particular settings for reuse.

               env = Environment()
               vars = Variables(['variables.cache', 'custom.py'])
               vars.Add(...)
               vars.Update(env)
               vars.Save('variables.cache', env)

       vars.GenerateHelpText(env, [sort])
           Generate help text documenting the customizable construction variables, suitable for
           passing in to the Help function.  env is the construction environment that will be
           used to get the actual values of the customizable variables. If the (optional) value
           of sort is callable, it is used as a comparison function to determine how to sort the
           added variables. This function must accept two arguments, compare them, and return a
           negative integer if the first is less-than the second, zero for equality, or a
           positive integer for greater-than. Optionally a Boolean value of True for sort will
           cause a standard alphabetical sort to be performed.

               Help(vars.GenerateHelpText(env))

               def cmp(a, b):
                   return (a > b) - (a < b)

               Help(vars.GenerateHelpText(env, sort=cmp))

       vars.FormatVariableHelpText(env, opt, help, default, actual)
           Returns a formatted string containing the printable help text for one option. It is
           normally not called directly, but is called by the GenerateHelpText method to create
           the returned help text. It may be overridden with your own function that takes the
           arguments specified above and returns a string of help text formatted to your liking.
           Note that GenerateHelpText will not put any blank lines or extra characters in between
           the entries, so you must add those characters to the returned string if you want the
           entries separated.

               def my_format(env, opt, help, default, actual):
                   fmt = "\n%s: default=%s actual=%s (%s)\n"
                   return fmt % (opt, default, actual, help)

               vars.FormatVariableHelpText = my_format

       To make it more convenient to work with customizable Variables, scons provides a number of
       functions that make it easy to set up various types of Variables. Each of these return a
       tuple ready to be passed to the Add or AddVariables method:

       BoolVariable(key, help, default)
           Return a tuple of arguments to set up a Boolean option. The option will use the
           specified name key, have a default value of default, and help will form the
           descriptive part of the help text. The option will interpret the command-line values
           y, yes, t, true, 1, on and all as true, and the command-line values n, no, f, false,
           0, off and none as false.

       EnumVariable(key, help, default, allowed_values, [map, ignorecase])
           Returns a tuple of arguments to set up an option whose value may be one of a specified
           list of legal enumerated values. The option will use the specified name key, have a
           default value of default, and help will form the descriptive part of the help text.
           The option will only support those values in the allowed_values list. The optional map
           argument is a dictionary that can be used to convert input values into specific legal
           values in the allowed_values list. If the value of ignore_case is 0 (the default),
           then the values are case-sensitive. If the value of ignore_case is 1, then values will
           be matched case-insensitively. If the value of ignore_case is 2, then values will be
           matched case-insensitively, and all input values will be converted to lower case.

       ListVariable(key, help, default, names, [map])
           Returns a tuple of arguments to set up an option whose value may be one or more of a
           specified list of legal enumerated values. The option will use the specified name key,
           have a default value of default, and help will form the descriptive part of the help
           text. The option will only accept the values “all”, “none”, or the values in the names
           list. More than one value may be specified, separated by commas. The default may be a
           string of comma-separated default values, or a list of the default values. The
           optional map argument is a dictionary that can be used to convert input values into
           specific legal values in the names list. (Note that the additional values accepted
           through the use of a map are not reflected in the generated help message).

       PackageVariable(key, help, default)
           Returns a tuple of arguments to set up an option whose value is a path name of a
           package that may be enabled, disabled or given an explicit path name. The option will
           use the specified name key, have a default value of default, and help will form the
           descriptive part of the help text. The option will support the values yes, true, on,
           enable or search, in which case the specified default will be used, or the option may
           be set to an arbitrary string (typically the path name to a package that is being
           enabled). The option will also support the values no, false, off or disable to disable
           use of the specified option.

       PathVariable(key, help, default, [validator])
           Returns a tuple of arguments to set up an option whose value is expected to be a path
           name. The option will use the specified name key, have a default value of default, and
           help will form the descriptive part of the help text. An additional validator may be
           specified that will be called to verify that the specified path is acceptable. SCons
           supplies the following ready-made validators:

           PathVariable.PathExists
               Verify that the specified path exists (this the default behavior if no validator
               is supplied).

           PathVariable.PathIsFile
               Verify that the specified path exists and is a regular file.

           PathVariable.PathIsDir
               Verify that the specified path exists and is a directory.

           PathVariable.PathIsDirCreate
               Verify that the specified path exists and is a directory; if it does not exist,
               create the directory.

           PathVariable.PathAccept
               Accept the specific path name argument without validation, suitable for when you
               want your users to be able to specify a directory path that will be created as
               part of the build process, for example.

           You may supply your own validator function, which must accept three arguments (key,
           the name of the variable to be set; val, the specified value being checked; and env,
           the construction environment) and should raise an exception if the specified value is
           not acceptable.

       These functions make it convenient to create a number of variables with consistent
       behavior in a single call to the AddVariables method:

           vars.AddVariables(
               BoolVariable(
                   "warnings",
                   help="compilation with -Wall and similar",
                   default=True,
               ),
               EnumVariable(
                   "debug",
                   help="debug output and symbols",
                   default="no",
                   allowed_values=("yes", "no", "full"),
                   map={},
                   ignorecase=0,  # case sensitive
               ),
               ListVariable(
                   "shared",
                   help="libraries to build as shared libraries",
                   default="all",
                   names=list_of_libs,
               ),
               PackageVariable(
                   "x11",
                   help="use X11 installed here (yes = search some places)",
                   default="yes",
               ),
               PathVariable(
                   "qtdir",
                   help="where the root of Qt is installed",
                   default=qtdir),
               PathVariable(
                   "foopath",
                   help="where the foo library is installed",
                   default=foopath,
                   validator=PathVariable.PathIsDir,
               ),
           )

   Node Objects
       SCons represents objects that are the sources or targets of build operations as Nodes,
       which are internal data structures. There are a number of user-visible types of nodes:
       File Nodes, Directory Nodes, Value Nodes and Alias Nodes. Some of the node types have
       public attributes and methods, described below. Each of the node types has a global
       function and a matching environment method to create instances: File, Dir, Value and
       Alias.

       Filesystem Nodes
           The File and Dir functions/methods return File and Directory Nodes, respectively. File
           and Directory Nodes (collectively, Filesystem Nodes) represent build components that
           correspond to an entry in the computer's filesystem, whether or not such an entry
           exists at the time the Node is created. You do not usually need to explicitly create
           filesystem Nodes, since when you supply a string as a target or source of a Builder,
           SCons will create the Nodes as needed to populate the dependency graph. Builders
           return the target Node(s) in the form of a list, which you can then make use of.
           However, since filesystem Nodes have some useful public attributes and methods that
           you can use in SConscript files, it is sometimes appropriate to create them manually,
           outside the regular context of a Builder call.

           The following attributes provide information about a Node:

           node.path
               The build path of the given file or directory. This path is relative to the
               top-level directory (where the SConstruct file is found). The build path is the
               same as the source path if variant_dir is not being used.

           node.abspath
               The absolute build path of the given file or directory.

           node.relpath
               The build path of the given file or directory relative to the root SConstruct
               file's directory.

           node.srcnode()
               The srcnode method returns another File or Directory Node representing the source
               path of the given File or Directory Node.

           Examples:

               # Get the current build dir's path, relative to top.
               Dir('.').path

               # Current dir's absolute path
               Dir('.').abspath

               # Current dir's path relative to the root SConstruct file's directory
               Dir('.').relpath

               # Next line is always '.', because it is the top dir's path relative to itself.
               Dir('#.').path

               # Source path of the given source file.
               File('foo.c').srcnode().path

               # Builders return lists of File objects:
               foo = env.Program('foo.c')
               print("foo will be built in", foo[0].path)

           Filesystem Node objects have methods to create new File and Directory Nodes relative
           to the original Node. There are also times when you may need to refer to an entry in a
           filesystem without knowing in advance whether it's a file or a directory. For those
           situations, there is an Entry method of filesystem node objects, which returns a Node
           that can represent either a file or a directory.

           If the original Node is a Directory Node, these methods will place the new Node within
           the directory the original Node represents:

           node.Dir(name)
               Returns a directory Node name which is a subdirectory of the directory represented
               by node.

           node.File(name)
               Returns a file Node name in the directory represented by node.

           node.Entry(name)
               Returns an unresolved Node name in the directory represented by node.

           If the original Node is a File Node, these methods will place the the new Node in the
           same directory as the one the original Node represents:

           node.Dir(name)
               Returns a Node name for a directory in the parent directory of the file
               represented by node.

           node.File(name)
               Returns a Node name for a file in the parent directory of the file represented by
               node.

           node.Entry(name)
               Returns an unresolved Node name in the parent directory of the file represented by
               node.

           For example:

               # Get a Node for a file within a directory
               incl = Dir('include')
               f = incl.File('header.h')

               # Get a Node for a subdirectory within a directory
               dist = Dir('project-3.2.1')
               src = dist.Dir('src')

               # Get a Node for a file in the same directory
               cfile = File('sample.c')
               hfile = cfile.File('sample.h')

               # Combined example
               docs = Dir('docs')
               html = docs.Dir('html')
               index = html.File('index.html')
               css = index.File('app.css')

       Value and Alias Nodes
           SCons provides two other Node types to represent object that will not have an
           equivalent filesystem entry. Such Nodes always need to be created explicitly.

           The Alias method returns an Alias Node. Aliases are virtual objects - they will not
           themselves result in physical objects being constructed, but are entered into the
           dependency graph related to their sources. An alias is checked for up to date by
           checking if its sources are up to date. An alias is built by making sure its sources
           have been built, and if any building took place, applying any Actions that are defined
           as part of the alias.

           An Alias call creates an entry in the alias namespace, which is used for
           disambiguation. If an alias source has a string valued name, it will be resolved to a
           filesystem entry Node, unless it is found in the alias namespace, in which case it it
           resolved to the matching alias Node. As a result, the order of Alias calls is
           significant. An alias can refer to another alias, but only if the other alias has
           previously been created.

           The Value method returns a Value Node. Value nodes are often used for generated data
           that will not have any corresponding filesystem entry, but will be used to determine
           whether a build target is out of date, or to include as part of a build Action. Common
           examples are timestamp strings, revision control version strings and other run-time
           generated strings.

           A Value Node can also be the target of a builder.

EXTENDING SCONS

       SCons is designed to be extensible through provided facilities, so changing the code of
       SCons itself is only rarely needed to customize its behavior. A number of the main
       operations use callable objects which can be supplemented by writing your own. Builders,
       Scanners and Tools each use a kind of plugin system, allowing you to easily drop in new
       ones. Information about creating Builder Objects and Scanner Objects appear in the
       following sections. The instructions SCons actually uses to construct things are called
       Actions, and it is easy to create Action Objects and hand them to the objects that need to
       know about those actions (besides Builders, see AddPostAction, AddPreAction and Alias for
       some examples of other places that take Actions).  Action Objects are also described
       below. Adding new Tool modules is described in Tool Modules

   Builder Objects
       scons can be extended to build different types of targets by adding new Builder objects to
       a construction environment.  In general, you should only need to add a new Builder object
       when you want to build a new type of file or other external target. For output file types
       scons already knows about, you can usually modify the behavior of premade Builders such as
       Program, Object or Library by changing the construction variables they use ($CC, $LINK,
       etc.). In this manner you can, for example, change the compiler to use, which is simpler
       and less error-prone than writing a new builder. The documentation for each Builder lists
       which construction variables it uses.

       Builder objects are created using the Builder factory function. Once created, a builder is
       added to an environment by entering it in the $BUILDERS dictionary in that environment
       (some of the examples in this section illustrate this). Doing so automatically triggers
       SCons to add a method with the name of the builder to the environment.

       The Builder function accepts the following keyword arguments:

       action
           The command used to build the target from the source.  action may be a string
           representing a template command line to execute, a list of strings representing the
           command to execute with its arguments (suitable for enclosing white space in an
           argument), a dictionary mapping source file name suffixes to any combination of
           command line strings (if the builder should accept multiple source file extensions), a
           Python function, an Action object (see Action Objects) or a list of any of the above.

           An action function must accept three arguments: source, target and env.  source is a
           list of source nodes; target is a list of target nodes; env is the construction
           environment to use for context.

           The action and generator arguments must not both be used for the same Builder.

       prefix
           The prefix to prepend to the target file name.  prefix may be a string, a function (or
           other callable) that takes two arguments (a construction environment and a list of
           sources) and returns a prefix string, or a dictionary specifying a mapping from a
           specific source suffix (of the first source specified) to a corresponding target
           prefix string. For the dictionary form, both the source suffix (key) and target prefix
           (value) specifications may use environment variable substitution, and the target
           prefix may also be a callable object. The default target prefix may be indicated by a
           dictionary entry with a key of None.

               b = Builder("build_it < $SOURCE > $TARGET",
                           prefix="file-")

               def gen_prefix(env, sources):
                   return "file-" + env['PLATFORM'] + '-'

               b = Builder("build_it < $SOURCE > $TARGET",
                           prefix=gen_prefix)

               b = Builder("build_it < $SOURCE > $TARGET",
                           suffix={None: "file-", "$SRC_SFX_A": gen_prefix})

       suffix
           The suffix to append to the target file name. Specified in the same manner as for
           prefix above. If the suffix is a string, then scons prepends a '.' to the suffix if
           it's not already there. The string returned by the callable object or obtained from
           the dictionary is untouched and you need to manually prepend a '.' if one is required.

               b = Builder("build_it < $SOURCE > $TARGET"
                           suffix="-file")

               def gen_suffix(env, sources):
                   return "." + env['PLATFORM'] + "-file"

               b = Builder("build_it < $SOURCE > $TARGET",
                           suffix=gen_suffix)

               b = Builder("build_it < $SOURCE > $TARGET",
                           suffix={None: ".sfx1", "$SRC_SFX_A": gen_suffix})

       ensure_suffix
           If set to a true value, ensures that targets will end in suffix. Thus, the suffix will
           also be added to any target strings that have a suffix that is not already suffix. The
           default behavior (also indicated by a false value) is to leave unchanged any target
           string that looks like it already has a suffix.

               b1 = Builder("build_it < $SOURCE > $TARGET"
                            suffix = ".out")
               b2 = Builder("build_it < $SOURCE > $TARGET"
                            suffix = ".out",
                            ensure_suffix=True)
               env = Environment()
               env['BUILDERS']['B1'] = b1
               env['BUILDERS']['B2'] = b2

               # Builds "foo.txt" because ensure_suffix is not set.
               env.B1('foo.txt', 'foo.in')

               # Builds "bar.txt.out" because ensure_suffix is set.
               env.B2('bar.txt', 'bar.in')

       src_suffix
           The expected source file name suffix.  src_suffix may be a string or a list of
           strings.

       target_scanner
           A Scanner object that will be invoked to find implicit dependencies for this target
           file. This keyword argument should be used for Scanner objects that find implicit
           dependencies based only on the target file and the construction environment, not for
           implicit dependencies based on source files. See the section called “Scanner Objects”
           for information about creating Scanner objects.

       source_scanner
           A Scanner object that will be invoked to find implicit dependencies in any source
           files used to build this target file. This is where you would specify a scanner to
           find things like #include lines in source files. The pre-built DirScanner Scanner
           object may be used to indicate that this Builder should scan directory trees for
           on-disk changes to files that scons does not know about from other Builder or function
           calls. See the section called “Scanner Objects” for information about creating your
           own Scanner objects.

       target_factory
           A factory function that the Builder will use to turn any targets specified as strings
           into SCons Nodes. By default, SCons assumes that all targets are files. Other useful
           target_factory values include Dir, for when a Builder creates a directory target, and
           Entry, for when a Builder can create either a file or directory target.

           Example:

               MakeDirectoryBuilder = Builder(action=my_mkdir, target_factory=Dir)
               env = Environment()
               env.Append(BUILDERS={'MakeDirectory': MakeDirectoryBuilder})
               env.MakeDirectory('new_directory', [])

           Note that the call to this MakeDirectory Builder needs to specify an empty source list
           to make the string represent the builder's target; without that, it would assume the
           argument is the source, and would try to deduce the target name from it, which in the
           absence of an automatically-added prefix or suffix would lead to a matching target and
           source name and a circular dependency.

       source_factory
           A factory function that the Builder will use to turn any sources specified as strings
           into SCons Nodes. By default, SCons assumes that all source are files. Other useful
           source_factory values include Dir, for when a Builder uses a directory as a source,
           and Entry, for when a Builder can use files or directories (or both) as sources.

           Example:

               CollectBuilder = Builder(action=my_mkdir, source_factory=Entry)
               env = Environment()
               env.Append(BUILDERS={'Collect': CollectBuilder})
               env.Collect('archive', ['directory_name', 'file_name'])

       emitter
           A function or list of functions to manipulate the target and source lists before
           dependencies are established and the target(s) are actually built.  emitter can also
           be a string containing a construction variable to expand to an emitter function or
           list of functions, or a dictionary mapping source file suffixes to emitter functions.
           (Only the suffix of the first source file is used to select the actual emitter
           function from an emitter dictionary.)

           A function passed as emitter must accept three arguments: source, target and env.
           source is a list of source nodes, target is a list of target nodes, env is the
           construction environment to use for context.

           An emitter must return a tuple containing two lists, the list of targets to be built
           by this builder, and the list of sources for this builder.

           Example:

               def e(target, source, env):
                   return target + ['foo.foo'], source + ['foo.src']

               # Simple association of an emitter function with a Builder.
               b = Builder("my_build < $TARGET > $SOURCE", emitter=e)

               def e2(target, source, env):
                   return target + ['bar.foo'], source + ['bar.src']

               # Simple association of a list of emitter functions with a Builder.
               b = Builder("my_build < $TARGET > $SOURCE", emitter=[e, e2])

               # Calling an emitter function through a construction variable.
               env = Environment(MY_EMITTER=e)
               b = Builder("my_build < $TARGET > $SOURCE", emitter='$MY_EMITTER')

               # Calling a list of emitter functions through a construction variable.
               env = Environment(EMITTER_LIST=[e, e2])
               b = Builder("my_build < $TARGET > $SOURCE", emitter='$EMITTER_LIST')

               # Associating multiple emitters with different file
               # suffixes using a dictionary.
               def e_suf1(target, source, env):
                   return target + ['another_target_file'], source

               def e_suf2(target, source, env):
                   return target, source + ['another_source_file']

               b = Builder(
                   action="my_build < $TARGET > $SOURCE",
                   emitter={'.suf1': e_suf1, '.suf2': e_suf2}
               )

       multi
           Specifies whether this builder is allowed to be called multiple times for the same
           target file(s). The default is False, which means the builder can not be called
           multiple times for the same target file(s). Calling a builder multiple times for the
           same target simply adds additional source files to the target; it is not allowed to
           change the environment associated with the target, specify additional environment
           overrides, or associate a different builder with the target.

       env
           A construction environment that can be used to fetch source code using this Builder.
           (Note that this environment is not used for normal builds of normal target files,
           which use the environment that was used to call the Builder for the target file.)

       generator
           A function that returns a list of actions that will be executed to build the target(s)
           from the source(s). The returned action(s) may be an Action object, or anything that
           can be converted into an Action object (see the next section).

           A function passed as generator must accept four arguments: source, target, env and
           for_signature.  source is a list of source nodes, target is a list of target nodes,
           env is the construction environment to use for context, and for_signature is a Boolean
           value that tells the function if it is being called for the purpose of generating a
           build signature (as opposed to actually executing the command). Since the build
           signature is used for rebuild determination, the function should omit those elements
           that do not affect whether a rebuild should be triggered if for_signature is true.

           Example:

               def g(source, target, env, for_signature):
                   return [["gcc", "-c", "-o"] + target + source]

               b = Builder(generator=g)

           The generator and action arguments must not both be used for the same Builder.

       src_builder
           Specifies a builder to use when a source file name suffix does not match any of the
           suffixes of the builder. Using this argument produces a multi-stage builder.

       single_source
           Specifies that this builder expects exactly one source file per call. Giving more than
           one source file without target files results in implicitly calling the builder
           multiple times (once for each source given). Giving multiple source files together
           with target files results in a UserError exception.

       source_ext_match
           When the specified action argument is a dictionary, the default behavior when a
           builder is passed multiple source files is to make sure that the extensions of all the
           source files match. If it is legal for this builder to be called with a list of source
           files with different extensions, this check can be suppressed by setting
           source_ext_match to False or some other non-true value. In this case, scons will use
           the suffix of the first specified source file to select the appropriate action from
           the action dictionary.

           In the following example, the setting of source_ext_match prevents scons from exiting
           with an error due to the mismatched suffixes of foo.in and foo.extra.

               b = Builder(action={'.in' : 'build $SOURCES > $TARGET'},
                           source_ext_match=False)

               env = Environment(BUILDERS={'MyBuild':b})
               env.MyBuild('foo.out', ['foo.in', 'foo.extra'])

       env
           A construction environment that can be used to fetch source code using this Builder.
           (Note that this environment is not used for normal builds of normal target files,
           which use the environment that was used to call the Builder for the target file.)

               b = Builder(action="build < $SOURCE > $TARGET")
               env = Environment(BUILDERS={'MyBuild' : b})
               env.MyBuild('foo.out', 'foo.in', my_arg='xyzzy')

       chdir
           A directory from which scons will execute the action(s) specified for this Builder. If
           the chdir argument is a string or a directory Node, scons will change to the specified
           directory. If the chdir is not a string or Node and is non-zero, then scons will
           change to the target file's directory.

           Note that scons will not automatically modify its expansion of construction variables
           like $TARGET and $SOURCE when using the chdir keyword argument--that is, the expanded
           file names will still be relative to the top-level directory containing the SConstruct
           file, and consequently incorrect relative to the chdir directory. Builders created
           using chdir keyword argument, will need to use construction variable expansions like
           ${TARGET.file} and ${SOURCE.file} to use just the filename portion of the targets and
           source.

               b = Builder(action="build < ${SOURCE.file} > ${TARGET.file}",
                           chdir=1)
               env = Environment(BUILDERS={'MyBuild' : b})
               env.MyBuild('sub/dir/foo.out', 'sub/dir/foo.in')

               Warning
               Python only keeps one current directory location even if there are multiple
               threads. This means that use of the chdir argument will not work with the SCons -j
               option, because individual worker threads spawned by SCons interfere with each
               other when they start changing directory.

       Any additional keyword arguments supplied when a Builder object is created (that is, when
       the Builder function is called) will be set in the executing construction environment when
       the Builder object is called. The canonical example here would be to set a construction
       variable to the repository of a source code system.

       Any such keyword arguments supplied when a Builder object is called will only be
       associated with the target created by that particular Builder call (and any other files
       built as a result of the call). These extra keyword arguments are passed to the following
       functions: command generator functions, function Actions, and emitter functions.

   Action Objects
       The Builder factory function will turn its action keyword argument into an appropriate
       internal Action object, as will the Command function. You can also explicitly create
       Action objects for passing to Builder, or other functions that take actions as arguments,
       by calling the Action factory function. This may more efficient when multiple Builder
       objects need to do the same thing rather than letting each of those Builder objects create
       a separate Action object. It also allows more flexible configuration of an Action object.
       For example, to control the message printed when the action is taken you need to create
       the action object using Action.

       The Action factory function returns an appropriate object for the action represented by
       the type of the action argument (the first positional parameter):

       •   If action is already an Action object, the object is simply returned.

       •   If action is a string, a command-line Action is returned. If such a string begins with
           @, the command line is not printed. If the string begins with hyphen (-), the exit
           status from the specified command is ignored, allowing execution to continue even if
           the command reports failure:

               Action('$CC -c -o $TARGET $SOURCES')

               # Doesn't print the line being executed.
               Action('@build $TARGET $SOURCES')

               # Ignores return value
               Action('-build $TARGET $SOURCES')

       •   If action is a list, then a list of Action objects is returned. An Action object is
           created as necessary for each element in the list. If an element within the list is
           itself a list, the embedded list is taken as the command and arguments to be executed
           via the command line. This allows white space to be enclosed in an argument rather
           than taken as a separator by defining a command in a list within a list:

               Action([['cc', '-c', '-DWHITE SPACE', '-o', '$TARGET', '$SOURCES']])

       •   If action is a callable object, a Function Action is returned. The callable must
           accept three keyword arguments: target, source and env.  target is a Node object
           representing the target file, source is a Node object representing the source file and
           env is the construction environment used for building the target file.

           The target and source arguments may be lists of Node objects if there is more than one
           target file or source file. The actual target and source file name(s) may be retrieved
           from their Node objects via the built-in Python str function:

               target_file_name = str(target)
               source_file_names = [str(x) for x in source]

           The function should return 0 or None to indicate a successful build of the target
           file(s). The function may raise an exception or return a non-zero exit status to
           indicate an unsuccessful build.

               def build_it(target=None, source=None, env=None):
                   # build the target from the source
                   return 0

               a = Action(build_it)

       •   If action is not one of the above types, no action object is generated and Action
           returns None.

       The environment method form env.Action will expand construction variables in any argument
       strings, including action, at the time it is called, using the construction variables in
       the construction environment through which it was called. The global function form Action
       delays variable expansion until the Action object is actually used.

       The optional second argument to Action is used to control the output which is printed when
       the Action is actually performed. If this parameter is omitted, or if the value is an
       empty string, a default output depending on the type of the action is used. For example, a
       command-line action will print the executed command. The following argument types are
       accepted:

       •   If the second argument is a string, or if the cmdstr keyword argument is supplied, the
           string defines what is printed. Substitution is performed on the string before it is
           printed. The string typically contains substitutable variables, notably $TARGET(S) and
           $SOURCE(S), or consists of just a single variable which is optionally defined
           somewhere else.  SCons itself heavily uses the latter variant.

       •   If the second argument is a function, or if the strfunction keyword argument is
           supplied, the function will be called to obtain the string to be printed when the
           action is performed. The function must accept three keyword arguments: target, source
           and env, with the same interpretation as for a callable action argument above. The
           function is responsible for handling any required substitutions.

       •   If the second argument is None, or if cmdstr=None is supplied, output is suppressed
           entirely.

       The cmdstr and strfunction keyword arguments may not both be supplied in a single call to
       Action

       Printing of action strings is affected by the setting of $PRINT_CMD_LINE_FUNC.

       Examples:

           def build_it(target, source, env):
               # build the target from the source
               return 0

           def string_it(target, source, env):
               return "building '%s' from '%s'" % (target[0], source[0])

           # Use a positional argument.
           f = Action(build_it, string_it)
           s = Action(build_it, "building '$TARGET' from '$SOURCE'")

           # Alternatively, use a keyword argument.
           f = Action(build_it, strfunction=string_it)
           s = Action(build_it, cmdstr="building '$TARGET' from '$SOURCE'")

           # You can provide a configurable variable.
           l = Action(build_it, '$STRINGIT')

       Any additional positional arguments, if present, may either be construction variables or
       lists of construction variables whose values will be included in the signature of the
       Action (the build signature) when deciding whether a target should be rebuilt because the
       action changed. Such variables may also be specified using the varlist keyword parameter;
       both positional and keyword forms may be present, and will be combined. This is necessary
       whenever you want a target to be rebuilt when a specific construction variable changes.
       This is not often needed for a string action, as the expanded variables will normally be
       part of the command line, but may be needed if a Python function action uses the value of
       a construction variable when generating the command line.

           def build_it(target, source, env):
               # build the target from the 'XXX' construction variable
               with open(target[0], 'w') as f:
                   f.write(env['XXX'])
               return 0

           # Use positional arguments.
           a = Action(build_it, '$STRINGIT', ['XXX'])

           # Alternatively, use a keyword argument.
           a = Action(build_it, varlist=['XXX'])

       The Action factory function can be passed the following optional keyword arguments to
       modify the Action object's behavior:

       chdir
           If chdir is true (the default is False), SCons will change directories before
           executing the action. If the value of chdir is a string or a directory Node, SCons
           will change to the specified directory. Otherwise, if chdir evaluates true, SCons will
           change to the target file's directory.

           Note that SCons will not automatically modify its expansion of construction variables
           like $TARGET and $SOURCE when using the chdir parameter - that is, the expanded file
           names will still be relative to the top-level directory containing the SConstruct
           file, and consequently incorrect relative to the chdir directory. Builders created
           using chdir keyword argument, will need to use construction variable expansions like
           ${TARGET.file} and ${SOURCE.file} to use just the filename portion of the targets and
           source. Example:

               a = Action("build < ${SOURCE.file} > ${TARGET.file}", chdir=True)

       exitstatfunc
           If provided, must be a callable which accepts a single parameter, the exit status (or
           return value) from the specified action, and which returns an arbitrary or modified
           value. This can be used, for example, to specify that an Action object's return value
           should be ignored under special conditions and SCons should, therefore, consider that
           the action always succeeds. Example:

               def always_succeed(s):
                   # Always return 0, which indicates success.
                   return 0

               a = Action("build < ${SOURCE.file} > ${TARGET.file}",
                          exitstatfunc=always_succeed)

       batch_key
           If provided, indicates that the Action can create multiple target files by processing
           multiple independent source files simultaneously. (The canonical example is "batch
           compilation" of multiple object files by passing multiple source files to a single
           invocation of a compiler such as Microsoft's Visual C / C++ compiler.) If the
           batch_key argument evaluates True and is not a callable object, the configured Action
           object will cause scons to collect all targets built with the Action object and
           configured with the same construction environment into single invocations of the
           Action object's command line or function. Command lines will typically want to use the
           $CHANGED_SOURCES construction variable (and possibly $CHANGED_TARGETS as well) to only
           pass to the command line those sources that have actually changed since their targets
           were built. Example:

               a = Action('build $CHANGED_SOURCES', batch_key=True)

           The batch_key argument may also be a callable function that returns a key that will be
           used to identify different "batches" of target files to be collected for batch
           building. A batch_key function must accept four parameters: action, env, target and
           source. The first parameter, action, is the active action object. The second
           parameter, env, is the construction environment configured for the target. The target
           and source parameters are the lists of targets and sources for the configured action.

           The returned key should typically be a tuple of values derived from the arguments,
           using any appropriate logic to decide how multiple invocations should be batched. For
           example, a batch_key function may decide to return the value of a specific
           construction variable from env which will cause scons to batch-build targets with
           matching values of that construction variable, or perhaps return the Python id() of
           the entire construction environment, in which case scons will batch-build all targets
           configured with the same construction environment. Returning None indicates that the
           particular target should not be part of any batched build, but instead will be built
           by a separate invocation of action's command or function. Example:

               def batch_key(action, env, target, source):
                   tdir = target[0].dir
                   if tdir.name == 'special':
                       # Don't batch-build any target
                       # in the special/ subdirectory.
                       return None
                   return (id(action), id(env), tdir)
               a = Action('build $CHANGED_SOURCES', batch_key=batch_key)

       Miscellaneous Action Functions
           SCons supplies Action functions that arrange for various common file and directory
           manipulations to be performed. These are similar in concept to "tasks" in the Ant
           build tool, although the implementation is slightly different. These functions do not
           actually perform the specified action at the time the function is called, but rather
           are factory functions which return an Action object that can be executed at the
           appropriate time.

           There are two natural ways that these Action Functions are intended to be used.

           First, if you need to perform the action at the time the SConscript file is being
           read, you can use the Execute global function:

               Execute(Touch('file'))

           Second, you can use these functions to supply Actions in a list for use by the
           env.Command method. This can allow you to perform more complicated sequences of file
           manipulation without relying on platform-specific external commands:

               env = Environment(TMPBUILD='/tmp/builddir')
               env.Command(
                   target='foo.out',
                   source='foo.in',
                   action=[
                       Mkdir('$TMPBUILD'),
                       Copy('$TMPBUILD', '${SOURCE.dir}'),
                       "cd $TMPBUILD && make",
                       Delete('$TMPBUILD'),
                   ],
               )

           Chmod(dest, mode)
               Returns an Action object that changes the permissions on the specified dest file
               or directory to the specified mode which can be octal or string, similar to the
               POSIX chmod command. Examples:

                   Execute(Chmod('file', 0o755))

                   env.Command(
                       'foo.out',
                       'foo.in',
                       [Copy('$TARGET', '$SOURCE'), Chmod('$TARGET', 0o755)],
                   )

                   Execute(Chmod('file', "ugo+w"))

                   env.Command(
                       'foo.out',
                       'foo.in',
                       [Copy('$TARGET', '$SOURCE'), Chmod('$TARGET', "ugo+w")],
                   )

               The behavior of Chmod is limited on Windows, see the notes in the Python
               documentation for os.chmod, which is the underlying function.

           Copy(dest, src)
               Returns an Action object that will copy the src source file or directory to the
               dest destination file or directory. If src is a list, dest must be a directory if
               it already exists. Examples:

                   Execute(Copy('foo.output', 'foo.input'))

                   env.Command('bar.out', 'bar.in', Copy('$TARGET', '$SOURCE'))

           Delete(entry, [must_exist])
               Returns an Action that deletes the specified entry, which may be a file or a
               directory tree. If a directory is specified, the entire directory tree will be
               removed. If the must_exist flag is set to a true value, then a Python error will
               be raised if the specified entry does not exist; the default is false, that is,
               the Action will silently do nothing if the entry does not exist. Examples:

                   Execute(Delete('/tmp/buildroot'))

                   env.Command(
                       'foo.out',
                       'foo.in',
                       action=[
                           Delete('${TARGET.dir}'),
                           MyBuildAction,
                       ],
                   )

                   Execute(Delete('file_that_must_exist', must_exist=True))

           Mkdir(name)
               Returns an Action that creates the directory name and all needed intermediate
               directories.  name may also be a list of directories to create. Examples:

                   Execute(Mkdir('/tmp/outputdir'))

                   env.Command(
                       'foo.out',
                       'foo.in',
                       action=[
                           Mkdir('/tmp/builddir'),
                           Copy('/tmp/builddir/foo.in', '$SOURCE'),
                           "cd /tmp/builddir && make",
                           Copy('$TARGET', '/tmp/builddir/foo.out'),
                       ],
                   )

           Move(dest, src)
               Returns an Action that moves the specified src file or directory to the specified
               dest file or directory. Examples:

                   Execute(Move('file.destination', 'file.source'))

                   env.Command(
                       'output_file',
                       'input_file',
                       action=[MyBuildAction, Move('$TARGET', 'file_created_by_MyBuildAction')],
                   )

           Touch(file)
               Returns an Action that updates the modification time on the specified file.
               Examples:

                   Execute(Touch('file_to_be_touched'))

                   env.Command('marker', 'input_file', action=[MyBuildAction, Touch('$TARGET')])

       Variable Substitution
           Before executing a command, scons performs parameter expansion (substitution) on the
           string that makes up the action part of the builder. The format of a substitutable
           parameter is ${expression}. If expression refers to a variable, the braces in
           ${expression} can be omitted unless the variable name is immediately followed by a
           character that could either be interpreted as part of the name, or is Python syntax
           such as [ (for indexing/slicing) or .  (for attribute access - see Special Attributes
           below).

           If expression refers to a construction variable, it is replaced with the value of that
           variable in the construction environment at the time of execution. If expression looks
           like a variable name but is not defined in the construction environment it is replaced
           with an empty string. If expression refers to one of the Special Variables (see below)
           the corresponding value of the variable is substituted.  expression may also be a
           Python expression to be evaluated. See Python Code Substitution below for a
           description.

           SCons uses the following rules when converting construction variables into command
           line strings:

           •   If the value is a string it is interpreted as space delimited command line
               arguments.

           •   If the value is a list it is interpreted as a list of command line arguments. Each
               element of the list is converted to a string.

           •   Anything that is not a list or string is converted to a string and interpreted as
               a single command line argument.

           •   Newline characters (\n) delimit lines. The newline parsing is done after all other
               parsing, so it is not possible for arguments (e.g. file names) to contain embedded
               newline characters.

           •   For a literal $ use $$. For example, $$FOO will be left in the final string as
               $FOO.

           When a build action is executed, a hash of the command line is saved, together with
           other information about the target(s) built by the action, for future use in rebuild
           determination. This is called the build signature (or build action signature). The
           escape sequence $( subexpression $) may be used to indicate parts of a command line
           that may change without causing a rebuild--that is, which are not to be included when
           calculating the build signature. All text from $( up to and including the matching $)
           will be removed from the command line before it is added to the build signature while
           only the $( and $) will be removed before the command is executed. For example, the
           command line string:

               "echo Last build occurred $( $TODAY $). > $TARGET"

           would execute the command:

               echo Last build occurred $TODAY. > $TARGET

           but the build signature added to any target files would be computed from:

               echo Last build occurred  . > $TARGET

           While construction variables are normally directly substituted, if a construction
           variable has a value which is a callable Python object (a function, or a class with a
           __call__ method), that object is called during substitution. The callable must accept
           four arguments: target, source, env and for_signature.  source is a list of source
           nodes, target is a list of target nodes, env is the construction environment to use
           for context, and for_signature is a boolean value that tells the callable if it is
           being called for the purpose of generating a build signature. Since the build
           signature is used for rebuild determination, variable elements that do not affect
           whether a rebuild should be triggered should be omitted from the returned string if
           for_signature is true. See $( and $) above for the syntax.

           SCons will insert whatever the callable returns into the expanded string:

               def foo(target, source, env, for_signature):
                   return "bar"

               # Will expand $BAR to "bar baz"
               env = Environment(FOO=foo, BAR="$FOO baz")

           As a reminder, substitution happens when $BAR is actually used in a builder action.
           The value of env['BAR'] will be exactly as it was set: "$FOO baz". This can make
           debugging tricky, as the substituted result is not available at the time the
           SConscript files are being interpreted and thus not available to the print function.
           However, you can perform the substitution on demand by calling the env.subst method
           for this purpose.

           You can use this feature to pass arguments to a callable variable by creating a
           callable class that stores passed arguments in the instance, and then uses them (in
           the __call__ method) when the instance is called. Note that in this case, the entire
           variable expansion must be enclosed by curly braces so that the arguments will be
           associated with the instantiation of the class:

               class foo:
                   def __init__(self, arg):
                       self.arg = arg

                   def __call__(self, target, source, env, for_signature):
                       return self.arg + " bar"

               # Will expand $BAR to "my argument bar baz"
               env=Environment(FOO=foo, BAR="${FOO('my argument')} baz")

       Substitution: Special Variables
           Besides regular construction variables, scons provides the following Special Variables
           for use in expanding commands:

           $CHANGED_SOURCES
               The file names of all sources of the build command that have changed since the
               target was last built.

           $CHANGED_TARGETS
               The file names of all targets that would be built from sources that have changed
               since the target was last built.

           $SOURCE
               The file name of the source of the build command, or the file name of the first
               source if multiple sources are being built.

           $SOURCES
               The file names of the sources of the build command.

           $TARGET
               The file name of the target being built, or the file name of the first target if
               multiple targets are being built.

           $TARGETS
               The file names of all targets being built.

           $UNCHANGED_SOURCES
               The file names of all sources of the build command that have not changed since the
               target was last built.

           $UNCHANGED_TARGETS
               The file names of all targets that would be built from sources that have not
               changed since the target was last built.

           These names are reserved and may not be assigned to or used as construction variables.
           SCons computes them in a context-dependent manner and they and are not retrieved from
           a construction environment.

           For example, the following builder call:

               env = Environment(CC='cc')
               env.Command(
                   target=['foo'],
                   source=['foo.c', 'bar.c'],
                   action='@echo $CC -c -o $TARGET $SOURCES'
               )

           would produce the following output:

               cc -c -o foo foo.c bar.c

           In the previous example, a string ${SOURCES[1]} would expand to: bar.c.

       Substitution: Special Attributes
           A variable name may have the following modifiers appended within the enclosing curly
           braces to access properties of the interpolated string. These are known as special
           attributes.
               base -
                   The base path of the file name,
                   including the directory path
                   but excluding any suffix.

               dir - The name of the directory in which the file exists.
               file -  The file name, minus any directory portion.
               filebase - Like file but minus its suffix.
               suffix - Just the file suffix.
               abspath - The absolute path name of the file.
               relpath - The path name of the file relative to the root SConstruct file's
               directory.
               posix -
                   The path with directories separated by forward slashes
                   (/).
                   Sometimes necessary on Windows systems
                   when a path references a file on other (POSIX) systems.

               windows -
                   The path with directories separated by backslashes
                   (\\).
                   Sometimes necessary on POSIX-style systems
                   when a path references a file on other (Windows) systems.
                   win32 is a (deprecated) synonym for
                   windows.

               srcpath -
                   The directory and file name to the source file linked to this file through
                   VariantDir().
                   If this file isn't linked,
                   it just returns the directory and filename unchanged.

               srcdir -
                   The directory containing the source file linked to this file through
                   VariantDir().
                   If this file isn't linked,
                   it just returns the directory part of the filename.

               rsrcpath -
                   The directory and file name to the source file linked to this file through
                   VariantDir().
                   If the file does not exist locally but exists in a Repository,
                   the path in the Repository is returned.
                   If this file isn't linked, it just returns the
                   directory and filename unchanged.

               rsrcdir -
                   The Repository directory containing the source file linked to this file
               through
                   VariantDir().
                   If this file isn't linked,
                   it just returns the directory part of the filename.

           For example, the specified target will expand as follows for the corresponding
           modifiers:

               $TARGET              => sub/dir/file.x
               ${TARGET.base}       => sub/dir/file
               ${TARGET.dir}        => sub/dir
               ${TARGET.file}       => file.x
               ${TARGET.filebase}   => file
               ${TARGET.suffix}     => .x
               ${TARGET.abspath}    => /top/dir/sub/dir/file.x
               ${TARGET.relpath}    => sub/dir/file.x

               $TARGET              => ../dir2/file.x
               ${TARGET.abspath}    => /top/dir2/file.x
               ${TARGET.relpath}    => ../dir2/file.x

               SConscript('src/SConscript', variant_dir='sub/dir')
               $SOURCE              => sub/dir/file.x
               ${SOURCE.srcpath}    => src/file.x
               ${SOURCE.srcdir}     => src

               Repository('/usr/repository')
               $SOURCE              => sub/dir/file.x
               ${SOURCE.rsrcpath}   => /usr/repository/src/file.x
               ${SOURCE.rsrcdir}    => /usr/repository/src

           Some modifiers can be combined, like ${TARGET.srcpath.base), ${TARGET.file.suffix},
           etc.

       Python Code Substitution
           If a substitutable expression using the notation ${expression} does not appear to
           match one of the other substitution patterns, it is evaluated as a Python expression.
           This uses Python's eval function, with the globals parameter set to the current
           environment's set of construction variables, and the result substituted in. So in the
           following case:

               env.Command(
                   'foo.out', 'foo.in', "echo ${COND==1 and 'FOO' or 'BAR'} > $TARGET"
               )

           the command executed will be either

               echo FOO > foo.out

           or

               echo BAR > foo.out

           according to the current value of env['COND'] when the command is executed. The
           evaluation takes place when the target is being built, not when the SConscript is
           being read. So if env['COND'] is changed later in the SConscript, the final value will
           be used.

           Here's a more complete example. Note that all of COND, FOO, and BAR are construction
           variables, and their values are substituted into the final command.  FOO is a list, so
           its elements are interpolated separated by spaces.

               env=Environment()
               env['COND'] = 1
               env['FOO'] = ['foo1', 'foo2']
               env['BAR'] = 'barbar'
               env.Command(
                   'foo.out', 'foo.in', "echo ${COND==1 and FOO or BAR} > $TARGET"
               )

           will execute:

               echo foo1 foo2 > foo.out

           In point of fact, Python expression evaluation is how the special attributes are
           substituted: they are simply attributes of the Python objects that represent $TARGET,
           $SOURCES, etc., which SCons passes to eval which returns the value.

               Caution
               Use of the Python eval function is considered to have security implications,
               since, depending on input sources, arbitrary unchecked strings of code can be
               executed by the Python interpreter. Although SCons makes use of it in a somewhat
               restricted context, you should be aware of this issue when using the
               ${python-expression-for-subst} form.

   Scanner Objects
       Scanner objects are used to scan specific file types for implicit dependencies, for
       example embedded preprocessor/compiler directives that cause other files to be included
       during processing.  SCons has a number of pre-built Scanner objects, so it is usually only
       necessary to set up Scanners for new file types. You do this by calling the Scanner
       factory function.  Scanner accepts the following arguments. Only function is required; the
       rest are optional:

       function
           A scanner function to call to process a given Node (usually a file) and return a list
           of Nodes representing the implicit dependencies (usually files) found in the contents.
           The function must accept three required arguments, node, env and path, and an optional
           fourth, arg.  node is the internal SCons node representing the file to scan, env is
           the construction environment to use during the scan, and path is a tuple of
           directories that can be searched for files, as generated by the optional scanner
           path_function (see below). If argument was supplied when the Scanner object was
           created, it is given as arg when the scanner function is called; since argument is
           optional, the default is no arg.

           The function can use use str(node) to fetch the name of the file, node.dir to fetch
           the directory the file is in, node.get_contents() to fetch the contents of the file as
           bytes or node.get_text_contents() to fetch the contents of the file as text.

           The function must take into account the path directories when generating the
           dependency Nodes. To illustrate this, a C language source file may contain a line like
           #include "foo.h". However, there is no guarantee that foo.h exists in the current
           directory: the contents of $CPPPATH is passed to the C preprocessor which will look in
           those places for the header, so the scanner function needs to look in those places as
           well in order to build Nodes with correct paths. Using FindPathDirs with an argument
           of CPPPATH as the path_function in the Scanner call means the scanner function will be
           called with the paths extracted from $CPPPATH in the environment env passed as the
           paths parameter.

           Note that the file to scan is not guaranteed to exist at the time the scanner is
           called - it could be a generated file which has not been generated yet - so the
           scanner function must be tolerant of that.

           Alternatively, you can supply a dictionary as the function parameter, to map keys
           (such as file suffixes) to other Scanner objects. A Scanner created this way serves as
           a dispatcher: the Scanner's skeys parameter is automatically populated with the
           dictionary's keys, indicating that the Scanner handles Nodes which would be selected
           by those keys; the mapping is then used to pass the file on to a different Scanner
           that would not have been selected to handle that Node based on its own skeys.

       name
           The name to use for the Scanner. This is mainly used to identify the Scanner
           internally. The default value is "NONE".

       argument
           If specified, will be passed to the scanner function function and the path function
           path_function when called, as the optional parameter each of those functions takes.

       skeys
           Scanner key(s) indicating the file types this scanner is associated with. Used
           internally to select an appropriate scanner. In the usual case of scanning for file
           names, this argument will be a list of suffixes for the different file types that this
           Scanner knows how to scan. If skeys is a string, it will be expanded into a list by
           the current environment.

       path_function
           A Python function that takes four or five arguments: a construction environment, a
           Node for the directory containing the SConscript file in which the first target was
           defined, a list of target nodes, a list of source nodes, and the value of argument if
           it was supplied when the Scanner was created. Must return a tuple of directories that
           can be searched for files to be returned by this Scanner object. (Note that the
           FindPathDirs function can be used to return a ready-made path_function for a given
           construction variable name, instead of having to write your own function from
           scratch.)

       node_class
           The class of Node that should be returned by this Scanner object. Any strings or other
           objects returned by the scanner function that are not of this class will be run
           through the function supplied by the node_factory argument. A value of None can be
           supplied to indicate no conversion; the default is to return File nodes.

       node_factory
           A Python function that will take a string or other object and turn it into the
           appropriate class of Node to be returned by this Scanner object, as indicated by
           node_class.

       scan_check
           A Python function that takes two arguments, a Node (file) and a construction
           environment, and returns whether the Node should, in fact, be scanned for
           dependencies. This check can be used to eliminate unnecessary calls to the scanner
           function when, for example, the underlying file represented by a Node does not yet
           exist.

       recursive
           Specifies whether this scanner should be re-invoked on the dependency files returned
           by the scanner. If omitted, the Node subsystem will only invoke the scanner on the
           file being scanned and not recurse. Recursion is needed when the files returned by the
           scanner may themselves contain further file dependencies, as in the case of
           preprocessor #include lines. A value that evaluates true enables recursion; recursive
           may be a callable function, in which case it will be called with a list of Nodes found
           and should return a list of Nodes that should be scanned recursively; this can be used
           to select a specific subset of Nodes for additional scanning.

       Once created, a Scanner can added to an environment by setting it in the $SCANNERS list,
       which automatically triggers SCons to also add it to the environment as a method. However,
       usually a scanner is not truly standalone, but needs to be plugged in to the existing
       selection mechanism for deciding how to scan source files based on filename extensions.
       For this, SCons has a global SourceFileScanner object that is used by the Object,
       SharedObject and StaticObject builders to decide which scanner should be used. You can use
       the SourceFileScanner.add_scanner() method to add your own Scanner object to the SCons
       infrastructure that builds target programs or libraries from a list of source files of
       different types:

           def xyz_scan(node, env, path):
               contents = node.get_text_contents()
               # Scan the contents and return the included files.

           XYZScanner = Scanner(xyz_scan)

           SourceFileScanner.add_scanner('.xyz', XYZScanner)

           env.Program('my_prog', ['file1.c', 'file2.f', 'file3.xyz'])

   Tool Modules
       Additional tools can be added to a project either by placing them in a site_tools
       subdirectory of a site directory, or in a custom location specified to scons by giving the
       toolpath keyword argument to Environment. A tool module is a form of Python module,
       invoked internally using the Python import mechanism, so a tool can consist either of a
       single source file taking the name of the tool (e.g.  mytool.py) or a directory taking the
       name of the tool (e.g.  mytool/) which contains at least an __init__.py file.

       The toolpath parameter takes a list as its value:

           env = Environment(tools=['default', 'foo'], toolpath=['tools'])

       This looks for a tool specification module (mytool.py, or directory mytool) in directory
       tools and in the standard locations, as well as using the ordinary default tools for the
       platform.

       Directories specified via toolpath are prepended to the existing tool path. The default
       tool path is any site_tools directories, so tools in a specified toolpath take priority,
       followed by tools in a site_tools directory, followed by built-in tools. For example,
       adding a tool specification module gcc.py to the toolpath directory would override the
       built-in gcc tool. The tool path is stored in the environment and will be used by
       subsequent calls to the Tool method, as well as by env.Clone.

           base = Environment(toolpath=['custom_path'])
           derived = base.Clone(tools=['custom_tool'])
           derived.CustomBuilder()

       A tool specification module must include two functions:

       generate(env, **kwargs)
           Modify the construction environment env to set up necessary construction variables,
           Builders, Emitters, etc., so the facilities represented by the tool can be executed.
           Care should be taken not to overwrite construction variables intended to be settable
           by the user. For example:

               def generate(env):
                   ...
                   if 'MYTOOL' not in env:
                       env['MYTOOL'] = env.Detect("mytool")
                   if 'MYTOOLFLAGS' not in env:
                       env['MYTOOLFLAGS'] = SCons.Util.CLVar('--myarg')
                   ...

           The generate function may use any keyword arguments that the user supplies via kwargs
           to vary its initialization.

       exists(env)
           Return a true value if the tool can be called in the context of env. else false.
           Usually this means looking up one or more known programs using the PATH from the
           supplied env, but the tool can make the exists decision in any way it chooses.

           Note
           At the moment, user-added tools do not automatically have their exists function
           called. As a result, it is recommended that the generate function be defensively coded
           - that is, do not rely on any necessary existence checks already having been
           performed. This is expected to be a temporary limitation, and the exists function
           should still be provided.

       The elements of the tools list may also be functions or callable objects, in which case
       the Environment method will call those objects to update the new construction environment
       (see Tool for more details):

           def my_tool(env):
               env['XYZZY'] = 'xyzzy'

           env = Environment(tools=[my_tool])

       The individual elements of the tools list may also themselves be lists or tuples of the
       form (toolname, kw_dict). SCons searches for the toolname specification file as described
       above, and passes kw_dict, which must be a dictionary, as keyword arguments to the tool's
       generate function. The generate function can use the arguments to modify the tool's
       behavior by setting up the environment in different ways or otherwise changing its
       initialization.

           # in tools/my_tool.py:
           def generate(env, **kwargs):
             # Sets MY_TOOL to the value of keyword 'arg1' '1' if not supplied
             env['MY_TOOL'] = kwargs.get('arg1', '1')

           def exists(env):
             return True

           # in SConstruct:
           env = Environment(tools=['default', ('my_tool', {'arg1': 'abc'})],
                             toolpath=['tools'])

       The tool specification (my_tool in the example) can use the $PLATFORM variable from the
       construction environment it is passed to customize the tool for different platforms.

       Tools can be "nested" - that is, they can be located within a subdirectory in the
       toolpath. A nested tool name uses a dot to represent a directory separator

           # namespaced builder
           env = Environment(ENV=os.environ.copy(), tools=['SubDir1.SubDir2.SomeTool'])
           env.SomeTool(targets, sources)

           # Search Paths
           # SCons\Tool\SubDir1\SubDir2\SomeTool.py
           # SCons\Tool\SubDir1\SubDir2\SomeTool\__init__.py
           # .\site_scons\site_tools\SubDir1\SubDir2\SomeTool.py
           # .\site_scons\site_tools\SubDir1\SubDir2\SomeTool\__init__.py

SYSTEM-SPECIFIC BEHAVIOR

       scons and its configuration files are very portable, due largely to its implementation in
       Python. There are, however, a few portability issues waiting to trap the unwary.

   .C File Suffix
       scons handles the upper-case .C file suffix differently, depending on the capabilities of
       the underlying system. On a case-sensitive system such as Linux or UNIX, scons treats a
       file with a .C suffix as a C++ source file. On a case-insensitive system such as Windows,
       scons treats a file with a .C suffix as a C source file.

   Fortran File Suffixes
       There are several ways source file suffixes impact the behavior of SCons when working with
       Fortran language code (not all are system-specific, but they are included here for
       completeness).

       As the Fortran language has evolved through multiple standards editions, projects might
       have a need to handle files from different language generations differently. To this end,
       SCons dispatches to a different compiler dialect setup (expressed as a set of construction
       variables) depending on the file suffix. By default, all of these setups start out the
       same, but individual construction variables can be modified as needed to tune a given
       dialect. Each of these dialacts has a tool specification module whose documentation
       describes the construction variables associated with that dialect: .f (as well as .for and
       .ftn) in fortran; (construction variables start with FORTRAN) .f77 in f77; (construction
       variables start with F77) .f90 in f90; (construction variables start with F90) .f95 in
       f95; (construction variables start with F95) .f03 in f03; (construction variables start
       with F03) .f08 in f08 (construction variables start with F08).

       While SCons recognizes multiple internal dialects based on filename suffixes, the
       convention of various available Fortran compilers is to assign an actual meaning to only
       two of these suffixes: .f (as well as .for and .ftn) refers to the fixed-format source
       code that was the only available option in FORTRAN 77 and earlier, and .f90 refers to
       free-format source code which became available as of the Fortran 90 standard. Some
       compilers recognize suffixes which correspond to Fortran specifications later then F90 as
       equivalent to .f90 for this purpose, while some do not - check the documentation for your
       compiler. An occasionally suggested policy suggestion is to use only .f and .f90 as
       Fortran filename suffixes. The fixed/free form determination can usually be controlled
       explicitly with compiler flags (e.g.  -ffixed-form for gfortran), overriding any
       assumption that may be made based on the source file suffix.

       The source file suffix does not imply conformance with the similarly-named Fortran
       standard - a suffix of .f08 does not mean you are compiling specifically for Fortran 2008.
       Normally, compilers provide command-line options for making this selection (e.g.
       -std=f2008 for gfortran).

       For dialects from F90 on (including the generic FORTRAN dialect), a suffix of .mod is
       recognized for Fortran modules. These files are a side effect of compiling a Fortran
       source file containing module declarations, and must be available when other code which
       declares that it uses the module is processed.  SCons does not currently have integrated
       support for submodules, introduced in the Fortran 2008 standard - the invoked compiler
       will produce results, but SCons will not recognize .smod files as tracked objects.

       On a case-sensitive system such as Linux or UNIX, a file with a an upper-cased suffix from
       the set .F, .FOR, .FTN, .F90, .F95, .F03 and .F08 is treated as a Fortran source file
       which shall first be run through the standard C preprocessor. The lower-cased versions of
       these suffixes do not trigger this behavior. On systems which do not distinguish between
       uppper and lower case in filenames, this behavior is not available, but files suffixed
       with either .FPP or .fpp are always passed to the preprocessor first. This matches the
       convention of gfortran from the GNU Compiler Collection, and also followed by certain
       other Fortran compilers. For these two suffixes, the generic FORTRAN dialect will be
       selected.

       SCons itself does not invoke the preprocessor, that is handled by the compiler, but it
       adds construction variables which are applicable to the preprocessor run. You can see this
       difference by examining $FORTRANPPCOM and $FORTRANPPCOMSTR which are used instead of
       $FORTRANCOM and $FORTRANCOMSTR for that dialect.

   Windows: Cygwin Tools and Cygwin Python vs. Windows Pythons
       Cygwin supplies a set of tools and utilities that let users work on a Windows system using
       a POSIX-like environment. The Cygwin tools, including Cygwin Python, do this, in part, by
       sharing an ability to interpret POSIX-style path names. For example, the Cygwin tools will
       internally translate a Cygwin path name like /cygdrive/c/mydir to an equivalent Windows
       pathname of C:/mydir (equivalent to C:\mydir).

       Versions of Python that are built for native Windows execution, such as the python.org and
       ActiveState versions, do not understand the Cygwin path name semantics. This means that
       using a native Windows version of Python to build compiled programs using Cygwin tools
       (such as gcc, bison and flex) may yield unpredictable results. "Mixing and matching" in
       this way can be made to work, but it requires careful attention to the use of path names
       in your SConscript files.

       In practice, users can sidestep the issue by adopting the following guidelines: When using
       Cygwin's gcc for compiling, use the Cygwin-supplied Python interpreter to run scons; when
       using Microsoft Visual C/C++ (or some other "native" Windows compiler) use the python.org,
       Microsoft Store, ActiveState or other native version of Python to run scons.

       This discussion largely applies to the msys2 environment as well (with the use of the
       mingw compiler toolchain), in particular the recommendation to use the msys2 version of
       Python if running scons from inside an msys2 shell.

   Windows: scons.bat file
       On Windows, if scons is executed via a wrapper scons.bat batch file, there are (at least)
       two ramifications. Note this is no longer the default - scons installed via Python''s pip
       installer will have an scons.exe which does not have these limitations:

       First, Windows command-line users that want to use variable assignment on the command line
       may have to put double quotes around the assignments, otherwise the Windows command shell
       will consume those as arguments to itself, not to scons:

           scons "FOO=BAR" "BAZ=BLEH"

       Second, the Cygwin shell does not recognize typing scons at the command line prompt as
       referring to this wrapper. You can work around this either by executing scons.bat
       (including the extension) from the Cygwin command line, or by creating a wrapper shell
       script named scons which invokes scons.bat.

   MinGW
       The MinGW bin directory must be in your PATH environment variable or the ['ENV']['PATH']
       construction variable for scons to detect and use the MinGW tools. When running under the
       native Windows Python; interpreter, scons will prefer the MinGW tools over the Cygwin
       tools, if they are both installed, regardless of the order of the bin directories in the
       PATH variable. If you have both MSVC and MinGW installed and you want to use MinGW instead
       of MSVC, then you must explicitly tell scons to use MinGW by passing tools=['mingw'] to
       the Environment function, because scons will prefer the MSVC tools over the MinGW tools.

ENVIRONMENT

       In general, scons is not controlled by environment variables set in the shell used to
       invoke it, leaving it up to the SConscript file author to import those if desired. However
       the following variables are imported by scons itself if set:

       SCONS_LIB_DIR
           Specifies the directory that contains the scons Python module directory. Normally
           scons can deduce this, but in some circumstances, such as working with a source
           release, it may be necessary to specify (for example,
           /home/aroach/scons-src-0.01/src/engine).

       SCONSFLAGS
           A string containing options that will be used by scons in addition to those passed on
           the command line. Can be used to reduce frequent retyping of common options. The
           contents of SCONSFLAGS are considered before any passed command line options, so the
           command line can be used to override SCONSFLAGS options if necessary.

       SCONS_CACHE_MSVC_CONFIG
           (Windows only). If set, save the shell environment variables generated when setting up
           the Microsoft Visual C++ compiler (and/or Build Tools) to a cache file, to give these
           settings persistence across scons invocations. Generating this information is
           relatively expensive, so using this option may aid performance where scons is run
           often, such as Continuous Integration setups.

           If set to a True-like value ("1", "true" or "True") will cache to a file named
           scons_msvc_cache.json in the user's home directory. If set to a pathname, will use
           that pathname for the cache.

           Note: this implementation may still be somewhat fragile. In case of problems, remove
           the cache file - recreating with fresh info normally resolves any issues.  SCons
           ignores failures reading or writing the cache file and will silently revert to
           non-cached behavior in such cases.

           New in 3.1 (experimental). The default cache file name was changed to its present
           value in 4.4, and contents were expanded.

       QTDIR
           If using the qt tool, this is the path to the Qt installation to build against.  SCons
           respects this setting because it is a long-standing convention in the Qt world, where
           multiple Qt installations are possible.

SEE ALSO

               The SCons User Guide at
               https://scons.org/doc/production/HTML/scons-user.html

           The SCons Design Document (old)

               The SCons Cookbook at
               https://scons-cookbook.readthedocs.io
               for examples of how to solve various problems with SCons.

               SCons source code
               on GitHub[8]

               The SCons API Reference
               https://scons.org/doc/production/HTML/scons-api/index.html
               (for internal details)

AUTHORS

       Originally: Steven Knight knight@baldmt.com and Anthony Roach aroach@electriceyeball.com.

       Since 2010: The SCons Development Team scons-dev@scons.org.

AUTHOR

       The SCons Development Team

COPYRIGHT

       Copyright © 2001 - 2021 The SCons Foundation

NOTES

        1. https://github.com/SCons/scons-contrib
           https://github.com/SCons/scons-contrib

        2. LLVM specification
           https://clang.llvm.org/docs/JSONCompilationDatabase.html

        3. JEP 313
           https:openjdk.java.net/jeps/313

        4. https://learn.microsoft.com/en-us/cpp/build/reference/vcxproj-file-structure
           https://learn.microsoft.com/en-us/cpp/build/reference/vcxproj-file-structure

        5. https://learn.microsoft.com/en-us/visualstudio/extensibility/internals/solution-dot-
           sln-file
           https://learn.microsoft.com/en-us/visualstudio/extensibility/internals/solution-dot-sln-file

        6. If no_progress is set via SetOption in an SConscript file (but not if set in a
           site_init.py file) there will still be an initial status message about reading
           SConscript files since SCons has to start reading them before it can see the
           SetOption.

        7. http://www.opensource.org/licenses/alphabetical
           http://www.opensource.org/licenses/alphabetical

        8. on GitHub
           https://github.com/SCons/scons

SCons __VERSION__ V<pubdate>Released Sun, 18 Jul 2021 17:34:05 -0700</pubdate>           SCONS(1)