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NAME

       cpp - The C Preprocessor

SYNOPSIS

       cpp [-Dmacro[=defn]...] [-Umacro]
           [-Idir...] [-iquotedir...]
           [-Wwarn...]
           [-M|-MM] [-MG] [-MF filename]
           [-MP] [-MQ target...]
           [-MT target...]
           [-P] [-fno-working-directory]
           [-x language] [-std=standard]
           infile outfile

       Only the most useful options are listed here; see below for the remainder.

DESCRIPTION

       The C preprocessor, often known as cpp, is a macro processor that is used automatically by
       the C compiler to transform your program before compilation.  It is called a macro
       processor because it allows you to define macros, which are brief abbreviations for longer
       constructs.

       The C preprocessor is intended to be used only with C, C++, and Objective-C source code.
       In the past, it has been abused as a general text processor.  It will choke on input which
       does not obey C's lexical rules.  For example, apostrophes will be interpreted as the
       beginning of character constants, and cause errors.  Also, you cannot rely on it
       preserving characteristics of the input which are not significant to C-family languages.
       If a Makefile is preprocessed, all the hard tabs will be removed, and the Makefile will
       not work.

       Having said that, you can often get away with using cpp on things which are not C.  Other
       Algol-ish programming languages are often safe (Pascal, Ada, etc.) So is assembly, with
       caution.  -traditional-cpp mode preserves more white space, and is otherwise more
       permissive.  Many of the problems can be avoided by writing C or C++ style comments
       instead of native language comments, and keeping macros simple.

       Wherever possible, you should use a preprocessor geared to the language you are writing
       in.  Modern versions of the GNU assembler have macro facilities.  Most high level
       programming languages have their own conditional compilation and inclusion mechanism.  If
       all else fails, try a true general text processor, such as GNU M4.

       C preprocessors vary in some details.  This manual discusses the GNU C preprocessor, which
       provides a small superset of the features of ISO Standard C.  In its default mode, the GNU
       C preprocessor does not do a few things required by the standard.  These are features
       which are rarely, if ever, used, and may cause surprising changes to the meaning of a
       program which does not expect them.  To get strict ISO Standard C, you should use the
       -std=c90, -std=c99 or -std=c11 options, depending on which version of the standard you
       want.  To get all the mandatory diagnostics, you must also use -pedantic.

       This manual describes the behavior of the ISO preprocessor.  To minimize gratuitous
       differences, where the ISO preprocessor's behavior does not conflict with traditional
       semantics, the traditional preprocessor should behave the same way.  The various
       differences that do exist are detailed in the section Traditional Mode.

       For clarity, unless noted otherwise, references to CPP in this manual refer to GNU CPP.

OPTIONS

       The C preprocessor expects two file names as arguments, infile and outfile.  The
       preprocessor reads infile together with any other files it specifies with #include.  All
       the output generated by the combined input files is written in outfile.

       Either infile or outfile may be -, which as infile means to read from standard input and
       as outfile means to write to standard output.  Also, if either file is omitted, it means
       the same as if - had been specified for that file.

       Unless otherwise noted, or the option ends in =, all options which take an argument may
       have that argument appear either immediately after the option, or with a space between
       option and argument: -Ifoo and -I foo have the same effect.

       Many options have multi-letter names; therefore multiple single-letter options may not be
       grouped: -dM is very different from -d -M.

       -D name
           Predefine name as a macro, with definition 1.

       -D name=definition
           The contents of definition are tokenized and processed as if they appeared during
           translation phase three in a #define directive.  In particular, the definition will be
           truncated by embedded newline characters.

           If you are invoking the preprocessor from a shell or shell-like program you may need
           to use the shell's quoting syntax to protect characters such as spaces that have a
           meaning in the shell syntax.

           If you wish to define a function-like macro on the command line, write its argument
           list with surrounding parentheses before the equals sign (if any).  Parentheses are
           meaningful to most shells, so you will need to quote the option.  With sh and csh,
           -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are given on the command line.  All
           -imacros file and -include file options are processed after all -D and -U options.

       -U name
           Cancel any previous definition of name, either built in or provided with a -D option.

       -undef
           Do not predefine any system-specific or GCC-specific macros.  The standard predefined
           macros remain defined.

       -I dir
           Add the directory dir to the list of directories to be searched for header files.

           Directories named by -I are searched before the standard system include directories.
           If the directory dir is a standard system include directory, the option is ignored to
           ensure that the default search order for system directories and the special treatment
           of system headers are not defeated .  If dir begins with "=", then the "=" will be
           replaced by the sysroot prefix; see --sysroot and -isysroot.

       -o file
           Write output to file.  This is the same as specifying file as the second non-option
           argument to cpp.  gcc has a different interpretation of a second non-option argument,
           so you must use -o to specify the output file.

       -Wall
           Turns on all optional warnings which are desirable for normal code.  At present this
           is -Wcomment, -Wtrigraphs, -Wmultichar and a warning about integer promotion causing a
           change of sign in "#if" expressions.  Note that many of the preprocessor's warnings
           are on by default and have no options to control them.

       -Wcomment
       -Wcomments
           Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a
           backslash-newline appears in a // comment.  (Both forms have the same effect.)

       -Wtrigraphs
           Most trigraphs in comments cannot affect the meaning of the program.  However, a
           trigraph that would form an escaped newline (??/ at the end of a line) can, by
           changing where the comment begins or ends.  Therefore, only trigraphs that would form
           escaped newlines produce warnings inside a comment.

           This option is implied by -Wall.  If -Wall is not given, this option is still enabled
           unless trigraphs are enabled.  To get trigraph conversion without warnings, but get
           the other -Wall warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wtraditional
           Warn about certain constructs that behave differently in traditional and ISO C.  Also
           warn about ISO C constructs that have no traditional C equivalent, and problematic
           constructs which should be avoided.

       -Wundef
           Warn whenever an identifier which is not a macro is encountered in an #if directive,
           outside of defined.  Such identifiers are replaced with zero.

       -Wunused-macros
           Warn about macros defined in the main file that are unused.  A macro is used if it is
           expanded or tested for existence at least once.  The preprocessor will also warn if
           the macro has not been used at the time it is redefined or undefined.

           Built-in macros, macros defined on the command line, and macros defined in include
           files are not warned about.

           Note: If a macro is actually used, but only used in skipped conditional blocks, then
           CPP will report it as unused.  To avoid the warning in such a case, you might improve
           the scope of the macro's definition by, for example, moving it into the first skipped
           block.  Alternatively, you could provide a dummy use with something like:

                   #if defined the_macro_causing_the_warning
                   #endif

       -Wendif-labels
           Warn whenever an #else or an #endif are followed by text.  This usually happens in
           code of the form

                   #if FOO
                   ...
                   #else FOO
                   ...
                   #endif FOO

           The second and third "FOO" should be in comments, but often are not in older programs.
           This warning is on by default.

       -Werror
           Make all warnings into hard errors.  Source code which triggers warnings will be
           rejected.

       -Wsystem-headers
           Issue warnings for code in system headers.  These are normally unhelpful in finding
           bugs in your own code, therefore suppressed.  If you are responsible for the system
           library, you may want to see them.

       -w  Suppress all warnings, including those which GNU CPP issues by default.

       -pedantic
           Issue all the mandatory diagnostics listed in the C standard.  Some of them are left
           out by default, since they trigger frequently on harmless code.

       -pedantic-errors
           Issue all the mandatory diagnostics, and make all mandatory diagnostics into errors.
           This includes mandatory diagnostics that GCC issues without -pedantic but treats as
           warnings.

       -M  Instead of outputting the result of preprocessing, output a rule suitable for make
           describing the dependencies of the main source file.  The preprocessor outputs one
           make rule containing the object file name for that source file, a colon, and the names
           of all the included files, including those coming from -include or -imacros command-
           line options.

           Unless specified explicitly (with -MT or -MQ), the object file name consists of the
           name of the source file with any suffix replaced with object file suffix and with any
           leading directory parts removed.  If there are many included files then the rule is
           split into several lines using \-newline.  The rule has no commands.

           This option does not suppress the preprocessor's debug output, such as -dM.  To avoid
           mixing such debug output with the dependency rules you should explicitly specify the
           dependency output file with -MF, or use an environment variable like
           DEPENDENCIES_OUTPUT.  Debug output will still be sent to the regular output stream as
           normal.

           Passing -M to the driver implies -E, and suppresses warnings with an implicit -w.

       -MM Like -M but do not mention header files that are found in system header directories,
           nor header files that are included, directly or indirectly, from such a header.

           This implies that the choice of angle brackets or double quotes in an #include
           directive does not in itself determine whether that header will appear in -MM
           dependency output.  This is a slight change in semantics from GCC versions 3.0 and
           earlier.

       -MF file
           When used with -M or -MM, specifies a file to write the dependencies to.  If no -MF
           switch is given the preprocessor sends the rules to the same place it would have sent
           preprocessed output.

           When used with the driver options -MD or -MMD, -MF overrides the default dependency
           output file.

       -MG In conjunction with an option such as -M requesting dependency generation, -MG assumes
           missing header files are generated files and adds them to the dependency list without
           raising an error.  The dependency filename is taken directly from the "#include"
           directive without prepending any path.  -MG also suppresses preprocessed output, as a
           missing header file renders this useless.

           This feature is used in automatic updating of makefiles.

       -MP This option instructs CPP to add a phony target for each dependency other than the
           main file, causing each to depend on nothing.  These dummy rules work around errors
           make gives if you remove header files without updating the Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency generation.  By default CPP takes
           the name of the main input file, deletes any directory components and any file suffix
           such as .c, and appends the platform's usual object suffix.  The result is the target.

           An -MT option will set the target to be exactly the string you specify.  If you want
           multiple targets, you can specify them as a single argument to -MT, or use multiple
           -MT options.

           For example, -MT '$(objpfx)foo.o' might give

                   $(objpfx)foo.o: foo.c

       -MQ target
           Same as -MT, but it quotes any characters which are special to Make.
           -MQ '$(objpfx)foo.o' gives

                   $$(objpfx)foo.o: foo.c

           The default target is automatically quoted, as if it were given with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.  The driver
           determines file based on whether an -o option is given.  If it is, the driver uses its
           argument but with a suffix of .d, otherwise it takes the name of the input file,
           removes any directory components and suffix, and applies a .d suffix.

           If -MD is used in conjunction with -E, any -o switch is understood to specify the
           dependency output file, but if used without -E, each -o is understood to specify a
           target object file.

           Since -E is not implied, -MD can be used to generate a dependency output file as a
           side-effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system header files.

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
           Specify the source language: C, C++, Objective-C, or assembly.  This has nothing to do
           with standards conformance or extensions; it merely selects which base syntax to
           expect.  If you give none of these options, cpp will deduce the language from the
           extension of the source file: .c, .cc, .m, or .S.  Some other common extensions for
           C++ and assembly are also recognized.  If cpp does not recognize the extension, it
           will treat the file as C; this is the most generic mode.

           Note: Previous versions of cpp accepted a -lang option which selected both the
           language and the standards conformance level.  This option has been removed, because
           it conflicts with the -l option.

       -std=standard
       -ansi
           Specify the standard to which the code should conform.  Currently CPP knows about C
           and C++ standards; others may be added in the future.

           standard may be one of:

           "c90"
           "c89"
           "iso9899:1990"
               The ISO C standard from 1990.  c90 is the customary shorthand for this version of
               the standard.

               The -ansi option is equivalent to -std=c90.

           "iso9899:199409"
               The 1990 C standard, as amended in 1994.

           "iso9899:1999"
           "c99"
           "iso9899:199x"
           "c9x"
               The revised ISO C standard, published in December 1999.  Before publication, this
               was known as C9X.

           "iso9899:2011"
           "c11"
           "c1x"
               The revised ISO C standard, published in December 2011.  Before publication, this
               was known as C1X.

           "gnu90"
           "gnu89"
               The 1990 C standard plus GNU extensions.  This is the default.

           "gnu99"
           "gnu9x"
               The 1999 C standard plus GNU extensions.

           "gnu11"
           "gnu1x"
               The 2011 C standard plus GNU extensions.

           "c++98"
               The 1998 ISO C++ standard plus amendments.

           "gnu++98"
               The same as -std=c++98 plus GNU extensions.  This is the default for C++ code.

       -I- Split the include path.  Any directories specified with -I options before -I- are
           searched only for headers requested with "#include "file""; they are not searched for
           "#include <file>".  If additional directories are specified with -I options after the
           -I-, those directories are searched for all #include directives.

           In addition, -I- inhibits the use of the directory of the current file directory as
           the first search directory for "#include "file"".

           This option has been deprecated.

       -nostdinc
           Do not search the standard system directories for header files.  Only the directories
           you have specified with -I options (and the directory of the current file, if
           appropriate) are searched.

       -nostdinc++
           Do not search for header files in the C++-specific standard directories, but do still
           search the other standard directories.  (This option is used when building the C++
           library.)

       -include file
           Process file as if "#include "file"" appeared as the first line of the primary source
           file.  However, the first directory searched for file is the preprocessor's working
           directory instead of the directory containing the main source file.  If not found
           there, it is searched for in the remainder of the "#include "..."" search chain as
           normal.

           If multiple -include options are given, the files are included in the order they
           appear on the command line.

       -imacros file
           Exactly like -include, except that any output produced by scanning file is thrown
           away.  Macros it defines remain defined.  This allows you to acquire all the macros
           from a header without also processing its declarations.

           All files specified by -imacros are processed before all files specified by -include.

       -idirafter dir
           Search dir for header files, but do it after all directories specified with -I and the
           standard system directories have been exhausted.  dir is treated as a system include
           directory.  If dir begins with "=", then the "=" will be replaced by the sysroot
           prefix; see --sysroot and -isysroot.

       -iprefix prefix
           Specify prefix as the prefix for subsequent -iwithprefix options.  If the prefix
           represents a directory, you should include the final /.

       -iwithprefix dir
       -iwithprefixbefore dir
           Append dir to the prefix specified previously with -iprefix, and add the resulting
           directory to the include search path.  -iwithprefixbefore puts it in the same place -I
           would; -iwithprefix puts it where -idirafter would.

       -isysroot dir
           This option is like the --sysroot option, but applies only to header files (except for
           Darwin targets, where it applies to both header files and libraries).  See the
           --sysroot option for more information.

       -imultilib dir
           Use dir as a subdirectory of the directory containing target-specific C++ headers.

       -isystem dir
           Search dir for header files, after all directories specified by -I but before the
           standard system directories.  Mark it as a system directory, so that it gets the same
           special treatment as is applied to the standard system directories.

           If dir begins with "=", then the "=" will be replaced by the sysroot prefix; see
           --sysroot and -isysroot.

       -iquote dir
           Search dir only for header files requested with "#include "file""; they are not
           searched for "#include <file>", before all directories specified by -I and before the
           standard system directories.

           If dir begins with "=", then the "=" will be replaced by the sysroot prefix; see
           --sysroot and -isysroot.

       -fdirectives-only
           When preprocessing, handle directives, but do not expand macros.

           The option's behavior depends on the -E and -fpreprocessed options.

           With -E, preprocessing is limited to the handling of directives such as "#define",
           "#ifdef", and "#error".  Other preprocessor operations, such as macro expansion and
           trigraph conversion are not performed.  In addition, the -dD option is implicitly
           enabled.

           With -fpreprocessed, predefinition of command line and most builtin macros is
           disabled.  Macros such as "__LINE__", which are contextually dependent, are handled
           normally.  This enables compilation of files previously preprocessed with "-E
           -fdirectives-only".

           With both -E and -fpreprocessed, the rules for -fpreprocessed take precedence.  This
           enables full preprocessing of files previously preprocessed with "-E
           -fdirectives-only".

       -fdollars-in-identifiers
           Accept $ in identifiers.

       -fextended-identifiers
           Accept universal character names in identifiers.  This option is enabled by default
           for C99 (and later C standard versions) and C++.

       -fno-canonical-system-headers
           When preprocessing, do not shorten system header paths with canonicalization.

       -fpreprocessed
           Indicate to the preprocessor that the input file has already been preprocessed.  This
           suppresses things like macro expansion, trigraph conversion, escaped newline splicing,
           and processing of most directives.  The preprocessor still recognizes and removes
           comments, so that you can pass a file preprocessed with -C to the compiler without
           problems.  In this mode the integrated preprocessor is little more than a tokenizer
           for the front ends.

           -fpreprocessed is implicit if the input file has one of the extensions .i, .ii or .mi.
           These are the extensions that GCC uses for preprocessed files created by -save-temps.

       -ftabstop=width
           Set the distance between tab stops.  This helps the preprocessor report correct column
           numbers in warnings or errors, even if tabs appear on the line.  If the value is less
           than 1 or greater than 100, the option is ignored.  The default is 8.

       -fdebug-cpp
           This option is only useful for debugging GCC.  When used with -E, dumps debugging
           information about location maps.  Every token in the output is preceded by the dump of
           the map its location belongs to.  The dump of the map holding the location of a token
           would be:

                   {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}

           When used without -E, this option has no effect.

       -ftrack-macro-expansion[=level]
           Track locations of tokens across macro expansions. This allows the compiler to emit
           diagnostic about the current macro expansion stack when a compilation error occurs in
           a macro expansion. Using this option makes the preprocessor and the compiler consume
           more memory. The level parameter can be used to choose the level of precision of token
           location tracking thus decreasing the memory consumption if necessary. Value 0 of
           level de-activates this option just as if no -ftrack-macro-expansion was present on
           the command line. Value 1 tracks tokens locations in a degraded mode for the sake of
           minimal memory overhead. In this mode all tokens resulting from the expansion of an
           argument of a function-like macro have the same location. Value 2 tracks tokens
           locations completely. This value is the most memory hungry.  When this option is given
           no argument, the default parameter value is 2.

           Note that "-ftrack-macro-expansion=2" is activated by default.

       -fexec-charset=charset
           Set the execution character set, used for string and character constants.  The default
           is UTF-8.  charset can be any encoding supported by the system's "iconv" library
           routine.

       -fwide-exec-charset=charset
           Set the wide execution character set, used for wide string and character constants.
           The default is UTF-32 or UTF-16, whichever corresponds to the width of "wchar_t".  As
           with -fexec-charset, charset can be any encoding supported by the system's "iconv"
           library routine; however, you will have problems with encodings that do not fit
           exactly in "wchar_t".

       -finput-charset=charset
           Set the input character set, used for translation from the character set of the input
           file to the source character set used by GCC.  If the locale does not specify, or GCC
           cannot get this information from the locale, the default is UTF-8.  This can be
           overridden by either the locale or this command-line option.  Currently the command-
           line option takes precedence if there's a conflict.  charset can be any encoding
           supported by the system's "iconv" library routine.

       -fworking-directory
           Enable generation of linemarkers in the preprocessor output that will let the compiler
           know the current working directory at the time of preprocessing.  When this option is
           enabled, the preprocessor will emit, after the initial linemarker, a second linemarker
           with the current working directory followed by two slashes.  GCC will use this
           directory, when it's present in the preprocessed input, as the directory emitted as
           the current working directory in some debugging information formats.  This option is
           implicitly enabled if debugging information is enabled, but this can be inhibited with
           the negated form -fno-working-directory.  If the -P flag is present in the command
           line, this option has no effect, since no "#line" directives are emitted whatsoever.

       -fno-show-column
           Do not print column numbers in diagnostics.  This may be necessary if diagnostics are
           being scanned by a program that does not understand the column numbers, such as
           dejagnu.

       -A predicate=answer
           Make an assertion with the predicate predicate and answer answer.  This form is
           preferred to the older form -A predicate(answer), which is still supported, because it
           does not use shell special characters.

       -A -predicate=answer
           Cancel an assertion with the predicate predicate and answer answer.

       -dCHARS
           CHARS is a sequence of one or more of the following characters, and must not be
           preceded by a space.  Other characters are interpreted by the compiler proper, or
           reserved for future versions of GCC, and so are silently ignored.  If you specify
           characters whose behavior conflicts, the result is undefined.

           M   Instead of the normal output, generate a list of #define directives for all the
               macros defined during the execution of the preprocessor, including predefined
               macros.  This gives you a way of finding out what is predefined in your version of
               the preprocessor.  Assuming you have no file foo.h, the command

                       touch foo.h; cpp -dM foo.h

               will show all the predefined macros.

               If you use -dM without the -E option, -dM is interpreted as a synonym for
               -fdump-rtl-mach.

           D   Like M except in two respects: it does not include the predefined macros, and it
               outputs both the #define directives and the result of preprocessing.  Both kinds
               of output go to the standard output file.

           N   Like D, but emit only the macro names, not their expansions.

           I   Output #include directives in addition to the result of preprocessing.

           U   Like D except that only macros that are expanded, or whose definedness is tested
               in preprocessor directives, are output; the output is delayed until the use or
               test of the macro; and #undef directives are also output for macros tested but
               undefined at the time.

       -P  Inhibit generation of linemarkers in the output from the preprocessor.  This might be
           useful when running the preprocessor on something that is not C code, and will be sent
           to a program which might be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to the output file, except
           for comments in processed directives, which are deleted along with the directive.

           You should be prepared for side effects when using -C; it causes the preprocessor to
           treat comments as tokens in their own right.  For example, comments appearing at the
           start of what would be a directive line have the effect of turning that line into an
           ordinary source line, since the first token on the line is no longer a #.

       -CC Do not discard comments, including during macro expansion.  This is like -C, except
           that comments contained within macros are also passed through to the output file where
           the macro is expanded.

           In addition to the side-effects of the -C option, the -CC option causes all C++-style
           comments inside a macro to be converted to C-style comments.  This is to prevent later
           use of that macro from inadvertently commenting out the remainder of the source line.

           The -CC option is generally used to support lint comments.

       -traditional-cpp
           Try to imitate the behavior of old-fashioned C preprocessors, as opposed to ISO C
           preprocessors.

       -trigraphs
           Process trigraph sequences.

       -remap
           Enable special code to work around file systems which only permit very short file
           names, such as MS-DOS.

       --help
       --target-help
           Print text describing all the command-line options instead of preprocessing anything.

       -v  Verbose mode.  Print out GNU CPP's version number at the beginning of execution, and
           report the final form of the include path.

       -H  Print the name of each header file used, in addition to other normal activities.  Each
           name is indented to show how deep in the #include stack it is.  Precompiled header
           files are also printed, even if they are found to be invalid; an invalid precompiled
           header file is printed with ...x and a valid one with ...! .

       -version
       --version
           Print out GNU CPP's version number.  With one dash, proceed to preprocess as normal.
           With two dashes, exit immediately.

ENVIRONMENT

       This section describes the environment variables that affect how CPP operates.  You can
       use them to specify directories or prefixes to use when searching for include files, or to
       control dependency output.

       Note that you can also specify places to search using options such as -I, and control
       dependency output with options like -M.  These take precedence over environment variables,
       which in turn take precedence over the configuration of GCC.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
           Each variable's value is a list of directories separated by a special character, much
           like PATH, in which to look for header files.  The special character,
           "PATH_SEPARATOR", is target-dependent and determined at GCC build time.  For Microsoft
           Windows-based targets it is a semicolon, and for almost all other targets it is a
           colon.

           CPATH specifies a list of directories to be searched as if specified with -I, but
           after any paths given with -I options on the command line.  This environment variable
           is used regardless of which language is being preprocessed.

           The remaining environment variables apply only when preprocessing the particular
           language indicated.  Each specifies a list of directories to be searched as if
           specified with -isystem, but after any paths given with -isystem options on the
           command line.

           In all these variables, an empty element instructs the compiler to search its current
           working directory.  Empty elements can appear at the beginning or end of a path.  For
           instance, if the value of CPATH is ":/special/include", that has the same effect as
           -I. -I/special/include.

       DEPENDENCIES_OUTPUT
           If this variable is set, its value specifies how to output dependencies for Make based
           on the non-system header files processed by the compiler.  System header files are
           ignored in the dependency output.

           The value of DEPENDENCIES_OUTPUT can be just a file name, in which case the Make rules
           are written to that file, guessing the target name from the source file name.  Or the
           value can have the form file target, in which case the rules are written to file file
           using target as the target name.

           In other words, this environment variable is equivalent to combining the options -MM
           and -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
           This variable is the same as DEPENDENCIES_OUTPUT (see above), except that system
           header files are not ignored, so it implies -M rather than -MM.  However, the
           dependence on the main input file is omitted.

SEE ALSO

       gpl(7), gfdl(7), fsf-funding(7), gcc(1), as(1), ld(1), and the Info entries for cpp, gcc,
       and binutils.

COPYRIGHT

       Copyright (c) 1987-2015 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the terms of
       the GNU Free Documentation License, Version 1.3 or any later version published by the Free
       Software Foundation.  A copy of the license is included in the man page gfdl(7).  This
       manual contains no Invariant Sections.  The Front-Cover Texts are (a) (see below), and the
       Back-Cover Texts are (b) (see below).

       (a) The FSF's Front-Cover Text is:

            A GNU Manual

       (b) The FSF's Back-Cover Text is:

            You have freedom to copy and modify this GNU Manual, like GNU
            software.  Copies published by the Free Software Foundation raise
            funds for GNU development.