plucky (3) critcl_package.3tcl.gz

Provided by: critcl_3.3.1+dfsg-1_amd64 bug

NAME

       critcl_package - CriTcl Package Reference

SYNOPSIS

       package require Tcl  8.6

       package require critcl  ?3.3.1?

       package require platform  ?1.0.2?

       package require md5  ?2?

       ::critcl::ccode fragment

       ::critcl::ccommand tclname cname

       ::critcl::ccommand tclname arguments body ?option value...?

       ::critcl::cdata tclname data

       ::critcl::cconst tclname resulttype value

       ::critcl::cdefines list of glob patterns ?namespace?

       ::critcl::cproc name arguments resulttype body ?option value...?

       ::critcl::cproc name arguments resulttype

       ::critcl::cinit text externals

       ::critcl::include path

       ::critcl::api import name version

       ::critcl::api function resulttype name arguments

       ::critcl::api header ?glob pattern...?

       ::critcl::api extheader ?file...?

       ::critcl::license author ?text...?

       ::critcl::summary text

       ::critcl::description text

       ::critcl::subject ?key...?

       ::critcl::meta key ?word...?

       ::critcl::meta? key

       ::critcl::buildrequirement script

       ::critcl::cheaders ?arg...?

       ::critcl::csources ?glob pattern...?

       ::critcl::clibraries ?glob pattern...?

       ::critcl::source glob pattern

       ::critcl::tsources glob pattern...

       ::critcl::owns glob pattern...

       ::critcl::cflags ?arg...?

       ::critcl::ldflags ?arg...?

       ::critcl::framework ?arg...?

       ::critcl::tcl version

       ::critcl::tk

       ::critcl::preload lib...

       ::critcl::debug area...

       ::critcl::check ?label? text

       ::critcl::checklink ?label? text

       ::critcl::msg ?-nonewline? msg

       ::critcl::print ?-nonewline? ?chan? msg

       ::critcl::compiled

       ::critcl::compiling

       ::critcl::done

       ::critcl::failed

       ::critcl::load

       ::critcl::config option ?val?

       ::critcl::cache ?path?

       ::critcl::clean_cache ?pattern...?

       ::critcl::readconfig path

       ::critcl::showconfig ?chan?

       ::critcl::showallconfig ?chan?

       ::critcl::chooseconfig target ?nomatcherr?

       ::critcl::setconfig target

       ::critcl::actualtarget

       ::critcl::buildforpackage ?flag?

       ::critcl::cnothingtodo file

       ::critcl::cresults ?file?

       ::critcl::crosscheck

       ::critcl::error msg

       ::critcl::knowntargets

       ::critcl::sharedlibext

       ::critcl::targetconfig

       ::critcl::buildplatform

       ::critcl::targetplatform

       ::critcl::cobjects ?glob pattern...?

       ::critcl::scan path

       ::critcl::name2c name

       ::critcl::argnames arguments

       ::critcl::argcnames arguments

       ::critcl::argcsignature arguments

       ::critcl::argvardecls arguments

       ::critcl::argconversion arguments ?n?

       ::critcl::argoptional arguments

       ::critcl::argdefaults arguments

       ::critcl::argsupport arguments

       ::critcl::userconfig define name description type ?default?

       ::critcl::userconfig query name

       ::critcl::userconfig set name value

       ::critcl::at::caller

       ::critcl::at::caller offset

       ::critcl::at::caller offset level

       ::critcl::at::here

       ::critcl::at::get*

       ::critcl::at::get

       ::critcl::at::= file line

       ::critcl::at::incr n...

       ::critcl::at::incrt str...

       ::critcl::at::caller!

       ::critcl::at::caller! offset

       ::critcl::at::caller! offset level

       ::critcl::at::here!

       ::critcl::collect_begin

       ::critcl::collect_end

       ::critcl::collect script

       ::critcl::make path contents

       ::preload library

________________________________________________________________________________________________________________

DESCRIPTION

       Be  welcome  to the C Runtime In Tcl (short: CriTcl), a system for embedding and using C code from within
       Tcl [http://core.tcl-lang.org/tcl] scripts.

       The critcl package is the core of the system.  For an overview of the complete system,  see  Introduction
       To  CriTcl.   For  the usage of the standalone critcl program, see CriTcl Application.  This core package
       maybe be used to embed C code into Tcl scripts.  It also provides access  to  the  internals  that  other
       parts  of  the core use and which are of interest to those wishing to understand the internal workings of
       the core and of the API it provides to the CriTcl Application.  These advanced  sections  are  marked  as
       such so that those simply wishing to use the package can skip them.

       This package resides in the Core Package Layer of CriTcl.

       +----------------+
       |Applications    |
       | critcl         |
       | critcl::app    |
       +----------------+

       *================*
       |Core Packages   |
       | critcl         |
       | critcl::util   |
       *================*

       +----------------+
       |Support Packages|
       | stubs::*       |
       | md5, platform  |
       |  ...           |
       +----------------+

API

       A short note ahead of the documentation: Instead of repeatedly talking about "a Tcl script with embbedded
       C code", or "a Tcl script containing CriTcl commands", we call such a script a  CriTcl  script.   A  file
       containing a CriTcl script usually has the extension .tcl or .critcl.

   EMBEDDED C CODE
       The  following commands append C code fragments to the current module.  Fragments appear in the module in
       the order they are appended, so the earlier fragments (variables, functions, macros, etc.) are visible to
       later fragments.

       ::critcl::ccode fragment
              Appends  the  C  code in fragment to the current module and returns the empty string.  See Runtime
              Behaviour.

       ::critcl::ccommand tclname cname
              As documented below, except that cname is the name of a C function that already exists.

       ::critcl::ccommand tclname arguments body ?option value...?
              Appends the code to create a Tcl command named tclname and a corresponding C function  whose  body
              is  body  and  which  behaves  as  documented for Tcl's own Tcl_CreateObjCommand [https://www.tcl-
              lang.org/man/tcl/TclLib/CrtObjCmd.htm].

              aguments is a list of zero to four names for the standard arguments clientdata, interp, objc,  and
              objv.   The  standard  default  names are used in place of any missing names.  This is a more low-
              level way than critcl::cproc to define a command, as processing of the items in objv  is  left  to
              the  author,  affording  complete  control over the handling of the arguments to the command.  See
              section Runtime Behaviour.

              Returns the empty string.

              Each option may be one of:

              -clientdata c-expression
                     Provides the client data for the new command.  NULL by default.

              -delproc c-expression
                     Provides   a    function    pointer    of    type    Tcl_CmdDeleteProc    [https://www.tcl-
                     lang.org/man/tcl/TclLib/CrtObjCmd.htm]  as the deletion function for the new command.  NULL
                     by default.

              -cname boolean
                     If false (the default), a name for the corresponding C function  is  automatically  derived
                     from  the fully-qualified tclname.  Otherwise, name of the C function is the last component
                     of tclname.

       ::critcl::cdata tclname data
              Appends the code to create a new Tcl command named tclname  which  returns  data  as  a  ByteArray
              result.

              Returns the empty string.

       ::critcl::cconst tclname resulttype value
              Appends the code to create a new Tcl command named tclname which returns the constant value having
              the Tcl type resulttype.  value can be a C macro or a function call (including the parentheses) to
              any  visible C function that does not take arguments.  Unlike critcl::cdata, resulttype can be any
              type known to critcl::cproc.  Its semantics are equivalent to:

                  cproc $tclname {} $resulttype "return $value ;"

       This is more efficient than critcl::cproc since there is no C function generated.

       Returns the empty string.

       ::critcl::cdefines list of glob patterns ?namespace?
              Arranges for C enum and #define values that match one of the  patterns  in  glob  patterns  to  be
              created  in  the  namespace  namespace, each variable having the same as the corresponding C item.
              The default namespace is the global namespace.  A pattern that matches nothing is ignored.

              The Tcl variables are created when the module is compiled, using  the  preprocessor  in  order  to
              properly find all matching C definitions.

              Produces no C code.  The desired C definitions must already exist.

       ::critcl::cproc name arguments resulttype body ?option value...?
              Appends  a  function  having  body  as  its  body,  another  shim  function  to perform the needed
              conversions,  and  the  code  to  create  a  corresponding  Tcl  command  named  tclname.   Unlike
              critcl::ccommand  the  arguments  and  result  are typed, and CriTcl generates the code to convert
              between Tcl_Obj values and C data types.  See also Runtime Behaviour.

              Returns the empty string.

              string option
                     Each may be one of:

                     -cname boolean
                            If false (the default), a name for the corresponding  C  function  is  automatically
                            derived  from the fully-qualified tclname.  Otherwise, name of the C function is the
                            last component of tclname.

                     -pass-cdata boolean
                            If false (the default), the shim function performing the conversion to and from  Tcl
                            level does not pass the ClientData as the first argument to the function.

                     -arg-offset int
                            A  non-negative  integer,  0  by  default, indicating the number of hidden arguments
                            preceding the actual procedure arguments.   Used  by  higher-order  code  generators
                            where  there  are  prefix  arguments which are not directly seen by the function but
                            which influence argument counting and extraction.

              string resulttype
                     May be a predefined or a custom type.  See CriTcl cproc Type Reference for the full list of
                     predefined  types  and  how to extend them.  Unless otherwise noted, the Tcl return code is
                     always TCL_OK.

              list arguments
                     Is a multi-dictionary where each key is an argument type and  its  value  is  the  argument
                     name.  For example:

                      int x int y

              Each argument name must be a valid C identifier.

              If  the name is a list containing two items, the first item is the name and the second item is the
              default value.  A limited form of variadic  arguments  can  be  accomplished  using  such  default
              values.  For example:

                      int {x 1}

                     Here x is an optional argument of type int with a default value of 1.

                     Argument  conversion  is completely bypassed when the argument is not provided, so a custom
                     converter doing validation does not get the chance to validate the default value.  In  this
                     case, the value should be checked in the body of the function.

                     Each argument type may be a predefined or custom type.  See CriTcl cproc Type Reference for
                     the full list of predefined types and how to extend them.

       ::critcl::cproc name arguments resulttype
              As documented below, but used when the C function named name already exists.

       ::critcl::cinit text externals
              Appends the C code in text and externals, but only after all the other fragments appended  by  the
              previously-listed  commands  regardless  of  their placement in the CriTcl script relative to this
              command.  Thus, all their content is visible.  See also Runtime Behaviour.

              The C code in text is placed into the body of the initialization function of  the  shared  library
              backing  the  CriTcl script, and is executed when this library is loaded into the interpreter.  It
              has access to the variable Tcl_Interp* interp referencing  the  Tcl  interpreter  currently  being
              initialized.

              externals  is  placed  outside and just before the initialization function, making it a good place
              for any external symbols required by initialization function, but which should not  be  accessible
              by any other parts of the C code.

              Calls to this command are cumulative.

              Returns the empty string.

       ::critcl::include path
              This command is a convenient shorthand for

              critcl::code {
                #include <${path}>
              }

   STUBS TABLE MANAGEMENT
       CriTcl  versions  3  and  later  provide critcl::api to create and manipulate stubs tables, Tcl's dynamic
       linking mechanism handling  the  resolution  of  symbols  between  C  extensions.   See  http://wiki.tcl-
       lang.org/285  for  an  introduction,  and  section  Stubs  Tables  for the details of CriTcl's particular
       variant.

       Importing stubs tables, i.e. APIs, from another extension:

       ::critcl::api import name version
              Adds the following include directives into the CriTcl script and each of its companion ".c" files:

              [1]    #include <name/nameDecls.h>

              [2]    #include <name/nameStubLib.h>

              Returns an error if "name" isn't in the search path for the compiler.   See  critcl::cheaders  and
              the critcl application's -I and -includedir options.

              Important:  If  name  is  a  fully-qualified name in a non-global namespace, e.g.  "c::stack", the
              namespace separators "::" are converted into underscores ("_") in path names, C code, etc.

              name/nameDecls.h contains the stubs table type declarations, mapping macros, etc., and may include
              package-specific  headers.   See critcl::api header, below.  An #include directive is added at the
              beginning of the generated code for CriTcl script and at the beginning of each  of  its  companion
              ".c" files.

              name/nameStubLib.h contains the stubs table variable definition and the function to initialize it.
              An #include directive for it is added to the initialization code for the  CriTcl  script  ,  along
              with a call to the initializer function.

              If  "name/name.decls"  accompanies name/nameDecls.h, it should contain the external representation
              of the stubs table used to generate the headers. The file is read and the internal  representation
              of  the  stubs  table  returned  for  use by the importing package.  Otherwise, the empy string is
              returned.

              One possible use would be the automatic generation of C code calling on the  functions  listed  in
              the imported API.

              When generating a TEA package the names of the imported APIs are used to declare configure options
              with which the user can declare a non-standard directory for the headers of the API. Any API  name
              is translated into a single configure option --with-name-include.

       Declaration and export of a stubs table, i.e. API, for the CriTcl script:

       ::critcl::api function resulttype name arguments
              Adds  to  the public API of the CriTcl script the signature for the function named name and having
              the signature specified by arguments and resulttype.  Code is generated for a ".decls"  file,  the
              corresponding public headers, and a stubs table usable by critcl::api import.

              arguments  is  a  multidict where each key is an argument type and its value is the argument name,
              and resulttype is a C type.

       ::critcl::api header ?glob pattern...?
              Each file matching a glob pattern is copied into the directory containing the  generated  headers,
              and an #include directive for it is added to "Decls.h" for the CriTcl script.  Returns an error if
              a glob pattern matches nothing.

              A pattern for a relative path is resolved relative to the directory containing the CriTcl script.

       ::critcl::api extheader ?file...?
              Like ::critcl::api header, but each file should exist in the external development environment.  An
              #include  directive  is  added  to  "fooDecls.h",  but  file  is  not copied to the package header
              directory. file is not a glob pattern as CriTcl has no context, i.e directory, in which to  expand
              such patterns.

       As  with  the  headers  for an imported API, an #include directive is added to the generated code for the
       CriTcl script and to each companion ".c" file.

       In "compile & run" mode the generated header files and any companion headers are  placed  in  the  Result
       Cache subdirectory for the CriTcl script. This directory is added to the include search path of any other
       package importing this API and and building in mode "compile & run".

       In "generate package" mode -includedir specifies the subdirectory in the package to place  the  generated
       headers  in.  This  directory  is  added  to  the  search paths for header files, ensuring that a package
       importing an API finds it if the package exporting that API used the same setting for -includedir.

       In "generate TEA" mode the static scanner recognizes critcl::api header as a source of  companion  files.
       It also uses data from calls to critcl::api import to add support for --with-foo-include options into the
       generated "configure(.in)" so that a user may specify custom locations for the headers  of  any  imported
       API.

   PACKAGE META DATA
       CriTcl  versions  3  and  later  can  create  TEApot meta-data to be placed into "teapot.txt" in a format
       suitable for use by the TEApot tools [http://docs.activestate.com/activetcl/8.5/tpm/toc.html].

       In version 2, some meta data support was already present through ::critcl::license,  but  this  was  only
       used to generate "license.txt".

       ::critcl::license author ?text...?
              Ignored in "compile & run" mode.

              In  "generate  package"  mode provides information about the author of the package and the license
              for the package.

              text  arguments  are  concatenated  to  form  the  text  of  the  license,  which  is  written  to
              "license.terms"  in  the  same directory as "pkgIndex.tcl".  If no text is provided the license is
              read from "license.terms" in the same directory as the CriTcl script.

              This information  takes  precedence  over  any  information  specified  through  the  generic  API
              ::critcl::meta.   It  is  additionally  placed into the meta data file "teapot.txt" under the keys
              as::author and license.

       ::critcl::summary text
              Ignored in "compile & run" mode.

              In "generate package" mode places a short, preferably one-line description of the package into the
              meta  data  file  "teapot.txt"  under  the  key  summary.   This information takes precedence over
              information specified through the generic API ::critcl::meta.

       ::critcl::description text
              Ignored in "compile & run" mode.

              In "generate package" mode places a longer description of the package  into  the  meta  data  file
              "teapot.txt", under the key description.  The data specified by this command takes precedence over
              any information specified through the generic API ::critcl::meta.

       ::critcl::subject ?key...?
              Ignored in "compile & run" mode.

              In "generate package" mode places each key into the meta data file  "teapot.txt",  under  the  key
              subject.  This information takes precedence over any information specified through the generic API
              ::critcl::meta.

              Calls to this command are cumulative.

       ::critcl::meta key ?word...?
              Provides arbitrary meta data outside of the following reserved keys: as::author,  as::build::date,
              description, license, name, platform, require subject, summary, and version, Its behaviour is like
              ::critcl::subject in that it treats all keys as list of words, with each  call  providing  one  or
              more  words  for  the  key,  and  multiple  calls  extending  the data for an existing key, if not
              reserved.

              While it is possible to declare information for one of the reserved keys with  this  command  such
              data is ignored when the final meta data is assembled and written.

              Use  the  commands  ::critcl::license, ::critcl::summary, ::critcl::description ::critcl::subject,
              package require, and package provide to declare data for the reserved keys.

              The information for the reserved keys as::build::date and platform is automatically  generated  by
              critcl itself.

       ::critcl::meta? key
              Returns the value in the metadata associated with key.

              Used  primarily to retrieve the name of the package from within utility packages having to adapt C
              code templates to their environment. For example, critcl::class uses does this.

       ::critcl::buildrequirement script
              Provides control over the capturing of  dependencies  declared  via  package  require.  script  is
              evaluated and any dependencies declared within are ignored, i.e. not recorded in the meta data.

   CONTROL & INTERFACE
       These  commands  control the details of compilation and linking a CriTcl script.  The information is used
       only to compile/link the object for the CriTcl script.  For example, information for  "FOO.tcl"  is  kept
       separate from information for "BAR.tcl".

       ::critcl::cheaders ?arg...?
              Provides additional header locations.

              Each  argument is a glob pattern.  If an argument begins with - it is an argument to the compiler.
              Otherwise the parent directory of each matching path is a directory  to  be  searched  for  header
              files.  Returns an error if a pattern matches no files.  A pattern for a relative path is resolved
              relative to the directory containing the CriTcl script.

              #include lines are not automatically generated for matching header files.  Use critcl::include  or
              critcl::ccode as necessary to add them.

              Calls to this command are cumulative.

       ::critcl::csources ?glob pattern...?
              Matching  paths  become inputs to the compilation of the current object along with the sources for
              the current CriTcl script.  Returns an error if no  paths  match  a  pattern.   A  pattern  for  a
              relative path is resolved relative to the directory containing the CriTcl script.

              Calls to this command are cumulative.

       ::critcl::clibraries ?glob pattern...?
              provides  the  link  step  with  additional  libraries and library locations.  A glob pattern that
              begins with - is added as an argument to the linker.  Otherwise matching files are linked into the
              shared  library.   Returns an error if no paths match a pattern.  A pattern for a relative path is
              resolved relative to the directory containing the CriTcl script.

              Calls to this command are cumulative.

       ::critcl::source glob pattern
              Evaluates as scripts the files matching each glob pattern.  Returns  an  error  if  there  are  no
              matching  files.   A  pattern for a relative path is resolved relative to the directory containing
              the CriTcl script.

       ::critcl::tsources glob pattern...
              Provides the information about additional Tcl script files to source when the  shared  library  is
              loaded.

              Matching  paths  are  made  available  to  the  generated shared library when it is loaded for the
              current CriTcl script.  Returns an error if a pattern matches no files.  A pattern for a  relative
              path is resolved relative to the directory containing the CriTcl script.

              Calls to this command are cumulative.

              After  the  shared  library has been loaded, the declared files are sourced in the same order that
              they were provided as arguments.

       ::critcl::owns glob pattern...
              Ignored in "compile and run" and "generate package" modes.   In  "generate  TEA"  mode  each  file
              matching  a  glob  pattern  is  a  file  to be included in the TEA extension but that could not be
              ascertained as such from previous commands  like  critcl::csources  and  critcl::tsources,  either
              because of they were specified dynamically or because they were directly sourced.

       ::critcl::cflags ?arg...?

              Each arg is an argument to the compiler.

              Calls to this command are cumulative.

       ::critcl::ldflags ?arg...?

              Each arg is an argument to the linker.

              Calls to this command are cumulative.

       ::critcl::framework ?arg...?
              Each  arg  is  the name of a framework to link on MacOS X.  This command is ignored if OS X is not
              the target so that frameworks can be specified unconditionally.

              Calls to this command are cumulative.

       ::critcl::tcl version
              Specifies the minimum version of the Tcl runtime to compile and link the package for.  The default
              is 8.4.

       ::critcl::tk
              Arranges to include the Tk headers and link to the Tk stubs.

       ::critcl::preload lib...
              Arranges for the external shared library lib to be loaded before the shared library for the CriTcl
              script is loaded.

              Calls to this command are cumulative.

              Each library FOO is searched for in the directories listed below, in the order listed.  The search
              stops at the first existing path.  Additional notes:

              •      platform is the placeholder for the target platform of the package.

              •      The  extension ".so" is the placeholder for whatever actual extension is used by the target
                     platform for its shared libraries.

              •      The search is relative to the current working directory.

              And now the paths, depending on the exact form of the library name:

              FOO

                     [1]    FOO.so

                     [2]    FOO/FOO.so

                     [3]    FOO/platform/FOO.so

              PATH/FOO
                     The exact set searched depends on the existence of  directory  "PATH/FOO".  If  it  exists,
                     critcl searches

                     [1]    FOO.so

                     [2]    PATH/FOO/FOO.so

                     [3]    PATH/FOO/platform/FOO.so

                     Otherwise it searches

                     [1]    FOO.so

                     [2]    PATH/FOO.so

                     [3]    PATH/platform/FOO.so

                     instead.

              /PATH/FOO
                     Even  when  specifying FOO with an absolute path the first path searched is relative to the
                     current working directory.

                     [1]    FOO.so

                     [2]    /PATH/FOO.so

                     [3]    /PATH/platform/FOO.so

              For developers who want to understand or modify the internals of the  critcl  package,  Preloading
              functionality explains how preloading is implemented.

       ::critcl::debug area...
              Specifies  what  debugging  features  to  activate.  Internally each area is translated into area-
              specific flags for the compiler which are then handed over to critcl::cflags.

              memory Specifies Tcl memory debugging.

              symbols
                     Specifies compilation and linking with debugging symbols for use by  a  debugger  or  other
                     tool.

              all    Specifies all available debugging.

   INTROSPECTION
       The following commands control compilation and linking.

       ::critcl::check ?label? text
              Returns a true if the C code in text compiles sucessfully, and false otherwise.  Used to check for
              availability of features in the build environment.  If provided, label is used  to  uniquely  mark
              the results in the generated log.

       ::critcl::checklink ?label? text
              Like  critcl::check  but also links the compiled objects, returning true if the link is successful
              and false otherwise.  If specified, label is used to uniquely mark the results  in  the  generated
              log.

       ::critcl::msg ?-nonewline? msg
              Scripts  using  critcl::check  and critcl::checklink can use this command to report results.  Does
              nothing in compile & run mode.  Tools like the CriTcl Aplication  may  redefine  this  command  to
              implement their own message reporting. For example, critcl::app and any packages built on it print
              messages to stdout.

       ::critcl::print ?-nonewline? ?chan? msg
              Used by the CriTcl internals to report activity.   By  default,  effectively  the  same  thing  as
              ::puts.   Tools  directly  using  either  the CriTcl package or the CriTcl application package may
              redefine this procedure to implement their own output functionality.

              For          example,          the          newest          revisions          of           Kettle
              [https://chiselapp.com/user/andreas_kupries/repository/Kettle/index]  use  this to highlight build
              warnings.

       ::critcl::compiled
              Returns true if the current CriTcl script is already compiled and false otherwise.

              Enables a CriTcl script used as its own Tcl companion file (see critcl::tsources)  to  distinguish
              between  being  sourced  for  compilation  in compile & run mode and being sourced from either the
              result of generate package mode or during the load phase of compile & run  mode.   The  result  is
              false in the first case and true in the later two cases.

       ::critcl::compiling
              Returns true if a working C compiler is available and false otherwise.

       ::critcl::done
              Returns  true  when  CriTcl  script has been built and false otherwise.  Only useful from within a
              CriTcl script.  Enables the Tcl parts of a CriTcl script to distinguish between  prebuilt  package
              mode and compile & run mode.

              See also Modes Of Operation/Use.

       ::critcl::failed
              Returns true if the CriTcl script could not be built, and false otherwise.  Forces the building of
              the package if it hasn't already been done, but not its loading.  Thus, a CriTcl script can  check
              itself for availability of the compiled components.  Only useful from within a CriTcl script.

       ::critcl::load
              Like  critcl::failed  except  that it also forces the loading of the generated shared library, and
              that it returns true on success and false on failure.  Thus, a CriTcl script can check itself  for
              availability of the compiled components.  Only useful from within a CriTcl script.

   BUILD MANAGEMENT
       The  following  command  manages global settings, i.e. configuration options which are independent of any
       CriTcl script.

       This command should not be needed to write a CriTcl script. It is a  management  command  which  is  only
       useful to the CriTcl Application or similar tools.

       ::critcl::config option ?val?
              Sets and returns the following global configuration options:

              force bool
                     When false (the default), the C files are not built if there is a cached shared library.

              lines bool
                     When true (the default), #line directives are embedded into the generated C code.

                     This  facility  requires  the use of a tclsh that provides info frame.  Otherwise, no #line
                     directives are emitted. The command is  supported  by  Tcl  8.5  and  higher.  It  is  also
                     supported by Tcl 8.4 provided that it was compiled with the define -DTCL_TIP280. An example
                     of such is ActiveState's ActiveTcl.

                     Developers of higher-level packages  generating  their  own  C  code,  either  directly  or
                     indirectly  through  critcl,  should also read section Advanced: Location management to see
                     how critcl helps them in generating their directives.  Examples of such packages come  with
                     critcl itself. See critcl::iassoc and critcl::class.

              trace bool
                     When  false  (the default), no code tracing the entry and exit of CriTcl-backed commands in
                     the CriTcl script is inserted.  Insertion of such code  implicitly  activates  the  tracing
                     facility in general.  See critcl::cutil.

              I path A single global include path to use for all files. Not set by default.

              combine enum

                     dynamic (the default)
                            Object files have the suffix _pic.

                     static Object files have the suffix _stub.

                     standalone
                            Object  files  have  no suffix, and the generated C files are compiled without using
                            Tcl/Tk stubs. The result are object files usable  for  static  linking  into  a  big
                            shell.

              language string

              keepsrc bool
                     When  false  (the  default), the generated ".c" files are deleted after the ".o" files have
                     been built.

              outdir directory
                     The directory where to place a generated shared library. By default, it is placed into  the
                     Result Cache.

   RESULT CACHE MANAGEMENT
       The  following commands control the Result Cache.  These commands are not needed to simply write a CriTcl
       script.

       ::critcl::cache ?path?
              Sets and returns the path to the directory for the package's result cache.

              The default location is "~/.critcl/[platform::generic]" and usually does not require any changes.

       ::critcl::clean_cache ?pattern...?
              Cleans the result cache, i.e. removes any and all files and directories in  it.  If  one  or  more
              patterns are specified then only the files and directories matching them are removed.

   BUILD CONFIGURATION
       The following commands manage the build configuration, i.e. the per-platform information about compilers,
       linkers, and their commandline options.  These commands are not needed to simply write a CriTcl script.

       ::critcl::readconfig path
              Reads the build configuration file at path and configures the package using  the  information  for
              the target platform.

       ::critcl::showconfig ?chan?
              Converts the active build configuration into a human-readable string and returns it, or if chan is
              provided prints the result to that channel.

       ::critcl::showallconfig ?chan?
              Converts the set of all known build configurations from the currently active  build  configuration
              file last set with critcl::readconfig into a string and returns it, or if chan is provided, prints
              it to that channel.

       ::critcl::chooseconfig target ?nomatcherr?
              Matches target against all known targets, returning a list containing all the matching ones.  This
              search is first done on an exact basis, and then via glob matching. If no known target matches the
              argument the default is to return an empty list. However, if the boolean nomatcherr  is  specified
              and set an error is thrown using critcl::error instead.

       ::critcl::setconfig target
              Configures the package to use the settings of target.

   TOOL API
       The  following  commands  provide  tools  like  CriTcl  Application  or similar with deeper access to the
       package's internals.  These commands are not needed to simply write a CriTcl script.

       ::critcl::actualtarget
              Returns the platform identifier for the target platform, i.e. the platform to  build  for.  Unlike
              ::critcl::targetplatform this is the true target, with any cross-compilation information resolved.

       ::critcl::buildforpackage ?flag?
              Signals  whether  the  next file is to be built for inclusion into a package. If not specified the
              flag defaults to true, i.e. building for a package. This  disables  a  number  of  things  in  the
              backend, namely the linking of that file into a shared library and the loading of that library. It
              is expected that the build results are later wrapped into a larger collection.

       ::critcl::cnothingtodo file
              Checks whether there is anything to build for file.

       ::critcl::cresults ?file?
              Returns information about building file, or info script If file is not provided.   The  result  in
              question is a dictionary containing the following items:

              clibraries
                     A list of external shared libraries and/or directories needed to link file.

              ldflags
                     A list of linker flags needed to link file.

              license
                     The text of the license for the package file is located in.

              mintcl The minimum version of Tcl required by the package file is in to run successfully. A proper
                     Tcl version number.

              objects
                     A list of object files to link into file.

              preload
                     A list of libraries to be preloaded in order to sucessfully load and use file.

              tk     true if file requires Tk and false otherwise.

              tsources
                     A list of companion ".tcl" files to source in order to load and use the CriTcl script file.

              log    The full build log generated by the  compiler/linker,  including  command  line  data  from
                     critcl, and other things.

              exl    The  raw  build  log generated by the compiler/linker. Contains the output generated by the
                     invoked applications.

       ::critcl::crosscheck
              Determines whether the package is configured for cross-compilation and prints  a  message  to  the
              standard error channel if so.

       ::critcl::error msg
              Used  to  report internal errors. The default implementation simply returns the error.  Tools like
              the CriTcl Application are allowed to redefine this procedure to perform their own  way  of  error
              reporting.  There  is one constraint they are not allowed to change: The procedure must not return
              to the caller.

       ::critcl::knowntargets
              Returns  a  list  of  the  identifiers  of  all  targets  found  during  the  last  invocation  of
              critcl::readconfig.

       ::critcl::sharedlibext
              Returns the file extension for shared libraries on the target platform.

       ::critcl::targetconfig
              Returns the identifier of the target to build for, as specified by either the user or the system.

       ::critcl::buildplatform
              Returns the identifier of the build platform, i.e. where the package is running on.

       ::critcl::targetplatform
              Returns  the  identifier  of the target platform, i.e. the platform to compile for. In contrast to
              ::critcl::actualtarget this may be the name of a cross-compilation target.

       ::critcl::cobjects ?glob pattern...?
              Like ::critcl::clibraries, but instead of matching libraries, each  glob  pattern  matches  object
              files  to  be  linked  into  the  shared  object (at compile time, not runtime). If a glob pattern
              matches nothing an error is returned.  Not listed in Control & Interface because it is of  no  use
              to package writers. Only tools like the CriTcl Application need it.

              A pattern for a relative path is resolved relative to the directory containing the CriTcl script.

              Calls to this command are cumulative.

       ::critcl::scan path
              The main entry point to CriTcl's static code scanner.  Used by tools to implement processing modes
              like the assembly of a directory hierarchy containing a TEA-lookalike buildystem, etc.

              Scans path and returns a dictionary containing the following items:

              version
                     Package version.

              org    Author(ing organization).

              files  List of the companion files, relative to the directory of the input file.

       ::critcl::name2c name
              Given the Tcl-level identifier name, returns a  list  containing  the  following  details  of  its
              conversion to C:

              •      Tcl namespace prefix

              •      C namespace prefix

              •      Tcl base name

              •      C base name

       For   use  by  utilities  that  provide  Tcl  commands  without  going  through  standard  commands  like
       critcl::ccommand or critcl::cproc.  critcl::class does this.

   ADVANCED: EMBEDDED C CODE
       For advanced use, the following commands used by critcl::cproc itself are exposed.

       ::critcl::argnames arguments
              Given an argument declaration as documented for critcl::cproc, returns a list of the corresponding
              user-visible names.

       ::critcl::argcnames arguments
              Given an argument declaration as documented for critcl::cproc, returns a list of the corresponding
              C variable names for the user-visible names. The names returned here match the names used  in  the
              declarations and code returned by ::critcl::argvardecls and ::critcl::argconversion.

       ::critcl::argcsignature arguments
              Given an argument declaration as documented for critcl::cproc, returns a list of the corresponding
              C parameter declarations.

       ::critcl::argvardecls arguments
              Given an argument declaration as documented for critcl::cproc, returns a list of the corresponding
              C  variable  declarations.   The  names  used  in  these  declarations match the names returned by
              ::critcl::argcnames.

       ::critcl::argconversion arguments ?n?
              Given an argument declaration as documented for critcl::cproc, returns a list of C code  fragments
              converting the user visible arguments found in the declaration from Tcl_Obj* to C types. The names
              used in these statements match the names returned by ::critcl::argcnames.

              The generated code assumes that the procedure arguments start at index n of the objv  array.   The
              default is 1.

       ::critcl::argoptional arguments
              Given  an  argument  declaration as documented for critcl::cproc, returns a list of boolean values
              indicating which arguments are optional (true), and which are not (false).

       ::critcl::argdefaults arguments
              Given an argument declaration as documented for  critcl::cproc,  returns  a  list  containing  the
              default values for all optional arguments.

       ::critcl::argsupport arguments
              Given  an argument declaration as documented for critcl::cproc, returns a list of C code fragments
              needed to define the necessary supporting types.

   CUSTOM BUILD CONFIGURATION
       This package provides one command for the management of package-specific, i.e. developer-specified custom
       build configuration options.

       ::critcl::userconfig define name description type ?default?
              This  command  defines  custom  build  configuration  option,  with description, type and optional
              default value.

              The type can be either bool, or a list of values.

              [1]    For bool the default value, if specified, must be a boolean. If  it  is  not  specified  it
                     defaults to true.

              [2]    For  a  list of values the default value, if specified, must be a value found in this list.
                     If it is not specified it defaults to the first value of the list.

       The description serves as in-code documentation of the meaning of the option and  is  otherwise  ignored.
       When  generating  a  TEA wrapper the description is used for the configure option derived from the option
       declared by the command.

       A boolean option FOO are translated into a pair of configure  options,  --enable-FOO  and  --disable-FOO,
       whereas an option whose type is a list of values is translated into a single configure option --with-FOO.

       ::critcl::userconfig query name
              This  command  queries the database of custom build configuration option for the current ".critcl"
              file and  returns  the  chosen  value.   This  may  be  the  default  if  no  value  was  set  via
              ::critcl::userconfig set.

              It  is  at  this  point  that  definitions  and  set  values are brought together, with the latter
              validated against the definition.

       ::critcl::userconfig set name value
              This command is for use by a tool, like the critcl application, to specify values for custom build
              configuration options.

              At  the  time this command is used only the association between option name and value is recorded,
              and nothing else is done. This behaviour is necessary as the system may not know if an  option  of
              the specified name exists when the command is invoked, nor its type.

              Any   and  all  validation  is  defered  to  when  the  value  of  an  option  is  asked  for  via
              ::critcl::userconfig query.

              This means that it is possible to set values for any option we  like,  and  the  value  will  take
              effect only if such an option is both defined and used later on.

   ADVANCED: LOCATION MANAGEMENT
       First a small introduction for whose asking themselves ´what is location management' ?

       By  default  critcl  embeds  #line  directives into the generated C code so that any errors, warnings and
       notes found by the C compiler during compilation will refer to the ".critcl" file the faulty  code  comes
       from, instead of the generated ".c" file.

       This  facility  requires the use of a tclsh that provides info frame.  Otherwise, no #line directives are
       emitted. The command is supported by Tcl 8.5 and higher. It is also supported by Tcl 8.4 provided that it
       was compiled with the define -DTCL_TIP280. An example of such is ActiveState's ActiveTcl.

       Most  users  will  not  care  about this feature beyond simply wanting it to work and getting proper code
       references when reading compiler output.

       Developers of higher-level packages generating their own C code however should care about this, to ensure
       that  their  generated  code  contains proper references as well. Especially as this is key to separating
       bugs concerning code generated by the package itself and bug in the user's code going into  the  package,
       if any.

       Examples  of such packages come with critcl itself, see the implementation of packages critcl::iassoc and
       critcl::class.

       To help such developers eight commands are provided to manage such location information. These are listed
       below.

       A  main concept is that they all operate on a single stored location, setting, returning and clearing it.
       Note that this location information is completely independent  of  the  generation  of  #line  directives
       within critcl itself.

       ::critcl::at::caller
              This  command  stores  the location of the caller of the current procedure as a tuple of file name
              and linenumber. Any previously stored location is overwritten.  The result of the command  is  the
              empty string.

       ::critcl::at::caller offset
              As  above, the stored line number is modified by the specified offset. In essence an implicit call
              of critcl::at::incr.

       ::critcl::at::caller offset level
              As above, but the level the location information is taken from is modified as well. Level 0 is the
              caller, -1 its caller, etc.

       ::critcl::at::here
              This  command  stores  the  current  location in the current procedure as a tuple of file name and
              linenumber. Any previously stored location is overwritten.  The result of the command is the empty
              string.

              In terms of ::critcl::at::caller this is equivalent to

                critcl::at::caller 0 1

       ::critcl::at::get*
              This command takes the stored location and returns a formatted #line directive ready for embedding
              into some C code. The stored location is left untouched.  Note that the directive contains its own
              closing newline.

              For  proper  nesting  and  use  it  is  recommended  that  such directives are always added to the
              beginning of a code fragment. This way, should deeper layers add their own directives  these  will
              come  before  ours  and  thus  be  inactive.  End  result is that the outermost layer generating a
              directive will 'win', i.e. have its directive used. As it should be.

       ::critcl::at::get
              This command is like the above, except that it also clears the stored location.

       ::critcl::at::= file line
              This command allows the caller to set the stored  location  to  anything  they  want,  outside  of
              critcl's control.  The result of the command is the empty string.

       ::critcl::at::incr n...

       ::critcl::at::incrt str...
              These  commands  allow  the  user  to  modify  the line number of the stored location, changing it
              incrementally. The increment is specified as either a series  of  integer  numbers  (incr),  or  a
              series  of  strings  to  consider  (incrt). In case of the latter the delta is the number of lines
              endings found in the strings.

       ::critcl::at::caller!

       ::critcl::at::caller! offset

       ::critcl::at::caller! offset level

       ::critcl::at::here!
              These are convenience commands combining caller and here with get. I.e. they  store  the  location
              and  immediately return it formatted as proper #line directive. Also note that after their use the
              stored location is cleared.

   ADVANCED: DIVERSIONS
       Diversions are for higher-level packages generating their own C code,  to  make  their  use  of  critcl's
       commands generating Embedded C Code easier.

       These  commands  normally  generate  all of their C code for the current ".critcl" file, which may not be
       what is wanted by a higher-level package.

       With a diversion the generator output can be redirected into memory and from there on  then  handled  and
       processed as the caller desires before it is committed to an actual ".c" file.

       An example of such a package comes with critcl itself, see the implementation of package critcl::class.

       To  help such developers three commands are provided to manage diversions and the collection of C code in
       memory. These are:

       ::critcl::collect_begin
              This command starts the diversion of C code collection into memory.

              The result of the command is the empty string.

              Multiple calls are allowed, with each call opening a new nesting level of diversion.

       ::critcl::collect_end
              This command end the diversion of C code collection into memory and returns the collected C code.

              If multiple levels of diversion are open the call only closes and returns the data from  the  last
              level.

              The command will throw an error if no diversion is active, indicating a mismatch in the pairing of
              collect_begin and collect_end.

       ::critcl::collect script
              This is a convenience command which runs the script under diversion and returns  the  collected  C
              code, ensuring the correct pairing of collect_begin and collect_end.

   ADVANCED: FILE GENERATION
       While  file  generation  is  related to the diversions explained in the previous section they are not the
       same.  Even so, like diversions this feature is for higher-level packages generating their own C code.

       Three examples of utility packages using this facility comes with critcl itself.  See the implementations
       of packages critcl::literals, critcl::bitmap, and critcl::enum.

       When  splitting  a  package  implementation  into  pieces it is often sensible to have a number of pure C
       companion files containing low-level code, yet these files may require information about the code in  the
       main  ".critcl" file. Such declarations are normally not exportable and using the stub table support does
       not make sense, as this is completely internal to the package.

       With the file generation command below the main ".critcl" file can generate any number  of  header  files
       for the C companions to pick up.

       ::critcl::make path contents
              This  command  creates  the file path in a location where the C companion files of the package are
              able to pick it up by simple inclusion of path during their compilation, without interfering  with
              the outer system at all.

              The generated file will contain the specified contents.

CONCEPTS

   MODES OF OPERATION/USE
       CriTcl can be used in three different modes of operation, called

       [1]    Compile & Run, and

       [2]    Generate Package

       [3]    Generate TEA Package

       Compile & Run was the original mode and is the default for critcl_pkg.  Collects the C fragments from the
       CriTcl script, builds them as needed, and caches the results to improve load times later.

       The second mode, Generate Package, was introduced  to  enable  the  creation  of  (prebuilt)  deliverable
       packages  which do not depend on the existence of a build system, i.e. C compiler, on the target machine.
       This was originally done through the experimental Critbind  tool,  and  is  now  handled  by  the  CriTcl
       Application, also named critcl.

       Newly  introduced  with  CriTcl  version  3  is  Generate  TEA  Package. This mode constructs a directory
       hierarchy from the package which can later be built like a regular TEA package, i.e. using

                .../configure --prefix ...
                make all isntall

       Regarding the caching of results please read the section about the Result Cache fore more details.

   RUNTIME BEHAVIOUR
       The default behaviour of critcl, the package is to defer the compilation, linking, and loading of  any  C
       code  as  much  as  possible, given that this is an expensive operation, mainly in the time required.  In
       other words, the C code embedded into a ".critcl" file  is  built  only  when  the  first  C  command  or
       procedure it provides is invoked.  This part of the system uses standard functionality built into the Tcl
       core, i.e. the auto_index variable to map from commands to scripts providing them and the unknown command
       using this information when the command is needed.

       A  limitation  of  this  behaviour  is  that  it  is not possible to just use info commands check for the
       existence of a critcl defined command. It is also necessary to search in the auto_index array, in case it
       has not been build yet.

       This  behaviour  can  be  changed  by using the control command critcl::load. When invoked, the building,
       including loading of the result, is forced. After this command has been  invoked  for  a  ".critcl"  file
       further definition of C code in this file is not allowed any longer.

   FILE MAPPING
       Each  ".critcl"  file  is backed by a single private ".c" file containing that code, plus the boilerplate
       necessary for its compilation and linking as a single shared library.

       The Embedded C Code fragments appear in that file in the exact  same  order  they  were  defined  in  the
       ".critcl"  file,  with  one  exception.  The  C  code  provided  via critcl::cinit is put after all other
       fragments.  In other words all fragments have access to the symbols defined by earlier fragments, and the
       critcl::cinit fragment has access to all, regardless of its placement in the ".critcl" file.

       Note:  A  limitation  of the current system is the near impossibility of C level access between different
       critcl-based packages. The issue  is  not  the  necessity  of  writing  and  sharing  the  proper  extern
       statements,  but  that  the  management  (export  and  import)  of  package-specific  stubs-tables is not
       supported. This means that dependent parts have to be forcibly loaded before their user,  with  all  that
       entails.  See  section Runtime Behaviour for the relevant critcl limitation, and remember that many older
       platforms do not support the necessary resolution of symbols, the reason why stubs were invented for  Tcl
       in the first place.

   RESULT CACHE
       The  compilation  of C code is time-consuming critcl not only defers it as much as possible, as described
       in section Runtime Behaviour, but also caches the results.

       This means that on the first use of a ".critcl" file "FOO.tcl"  the  resulting  object  file  and  shared
       library  are  saved  into  the  cache,  and  on future uses of the same file reused, i.e. loaded directly
       without requiring compilation, provided that the contents of "FOO.tcl" did not change.

       The change detection is based MD5 hashes. A single hash is computed for each  ".critcl"  file,  based  on
       hashes  for  all  C code fragments and configuration options, i.e. everything which affects the resulting
       binary.

       As long as the input file doesn't change as per the hash a previously built shared library found  in  the
       cache is reused, bypassing the compilation and link stages.

       The command to manage the cache are found in section Result Cache Management.  Note however that they are
       useful only to tools based on the package, like the CriTcl Application. Package writers have no  need  of
       them.

       As  a  last  note,  the  default directory for the cache is chosen based on the chosen build target. This
       means that the cache can be put on a shared (network) filesystem  without  having  to  fear  interference
       between machines of different architectures.

   PRELOADING FUNCTIONALITY
       The  audience  of  this section are developers wishing to understand and possibly modify the internals of
       critcl package and application.  Package writers can skip this section.

       It explains how the preloading of external libraries is realized.

       Whenever a package declares libraries for preloading  critcl  will  build  a  supporting  shared  library
       providing  a Tcl package named "preload".  This package is not distributed separately, but as part of the
       package requiring the preload functionality.  This support package exports a single Tcl command

       ::preload library
              which is invoked once per libraries to preload, with  the  absolute  path  of  that  library.  The
              command then loads the library.

              On  windows  the  command  will further use the Tcl command ::critcl::runtime::precopy to copy the
              library to the disk, should its path be in a virtual filesystem which doesn't directly support the
              loading of a shared library from it.

       The  command ::critcl::runtime::precopy is provided by the file "critcl-rt.tcl" in the generated package,
       as is the command ::critcl::runtime::loadlib which  generates  the  ifneeded  script  expected  by  Tcl's
       package management. This generated ifneeded script contains the invocations of ::preload.

       The  C  code  for  the supporting library is found in the file "critcl_c/preload.c", which is part of the
       critcl package.

       The Tcl code for the supporting runtime "critcl-rt.tcl" is found in the file "runtime.tcl", which is part
       of the critcl::app package.

   CONFIGURATION INTERNALS
       The  audience  of  this section are developers wishing to understand and possibly modify the internals of
       critcl package and application.  Package writers can skip this section.

       It explains the syntax of configuration files and the configuration keys used by critcl to configure  its
       build backend, i.e. how this part of the system accesses compiler, linker, etc.

       It  is  recommended  to open the file containing the standard configurations ("path/to/critcl/Config") in
       the editor of your choice when reading this section of the documentation, using it as an extended set  of
       examples going beyond the simple defaults shown here.

       First,  the  keys  and  the meaning of their values, plus examples drawn from the standard configurations
       distributed with the package.  Note that when writing a custom  configuration  it  is  not  necessary  to
       specify  all the keys listed below, but only those whose default values are wrong or insufficient for the
       platform in question.

       version
              The command to print the compiler version number.  Defaults to

               gcc -v

       compile
              The command to compile a single C source file to an object file.  Defaults to

               gcc -c -fPIC

       debug_memory
              The list of flags for the compiler to enable memory debugging in Tcl.  Defaults to

               -DTCL_MEM_DEBUG

       debug_symbols
              The list of flags for the compiler to add symbols to the object files and the  resulting  library.
              Defaults to

               -g

       include
              The compiler flag to add an include directory.  Defaults to

               -I

       tclstubs
              The compiler flag to set USE_TCL_STUBS.  Defaults to

               -DUSE_TCL_STUBS

       tkstubs
              The compiler flag to set USE_TK_STUBS.  Defaults to

               -DUSE_TK_STUBS

       threadflags
              The list of compiler flags to enable a threaded build.  Defaults to

                  -DUSE_THREAD_ALLOC=1 -D_REENTRANT=1 -D_THREAD_SAFE=1
                  -DHAVE_PTHREAD_ATTR_SETSTACKSIZE=1 -DHAVE_READDIR_R=1
                  -DTCL_THREADS=1

       .

       noassert
              The compiler flag to turn off assertions in Tcl code.  Defaults to

               -DNDEBUG

       optimize
              The compiler flag to specify optimization level.  Defaults to

               -O2

       output The compiler flags to set the output file of a compilation.  Defaults to

               -o [list $outfile]

       NOTE the use of Tcl commands and variables here.  At the time critcl uses the value of this key the value
       of the referenced variable is substituted into it. The named variable is the only variable whose value is
       defined for this substitution.

       object The file extension for object files on the platform.  Defaults to

               .o

       preproc_define
              The  command  to  preprocess  a  C  source file without compiling it, but leaving #define's in the
              output. Defaults to

               gcc -E -dM

       preproc_enum
              See preproc_define, except that #define's are not left in the output. Defaults to

               gcc -E

       link   The command to link one or more object files and create a shared library. Defaults to

               gcc -shared

       link_preload
              The list of linker flags to use when dependent libraries are pre-loaded. Defaults to

               --unresolved-symbols=ignore-in-shared-libs

       strip  The flag to tell the linker to strip symbols from the shared library.  Defaults to

               -Wl,-s

       ldoutput
              Like output, but for the linker.  Defaults to the value of output.

       link_debug
              The list of linker flags needed to build a shared library with  symbols.  Defaults  to  the  empty
              string.  One platform requiring this are all variants of Windows, which uses

               -debug:full -debugtype:cv

       link_release
              The  list  of linker flags needed to build a shared library without symbols, i.e. a regular build.
              Defaults to the empty string.  One platform requiring this are all variants of Windows, which uses

               -release -opt:ref -opt:icf,3 -ws:aggressive

       sharedlibext
              The file extension for shared library files on the platform.  Defaults to

               [info sharedlibextension]

       platform
              The identifier of the platform used in generated packages.  Defaults to

               [platform::generic]

       target The presence of this key marks the configuration as a cross-compilation target and  the  value  is
              the actual platform identifier of the target.  No default.

       The syntax expected from configuration files is governed by the rules below.  Again, it is recommended to
       open the file containing the standard configurations ("path/to/critcl/Config")  in  the  editor  of  your
       choice  when  reading  this section of the documentation, using it as an extended set of examples for the
       syntax>

       [1]    Each logical line of the configuration file consists of one or more physical lines. In case of the
              latter  the  physical  lines  have  to follow each other and all but the first must be marked by a
              trailing backslash. This is the same marker for continuation lines as used by Tcl itself.

       [2]    A (logical) line starting with the character "#" (modulo whitespace) is a comment which runs until
              the end of the line, and is otherwise ignored.

       [3]    A  (logical)  line  starting  with  the  word  "if" (modulo whitespace) is interpreted as Tcl's if
              command and executed as such. I.e. this command has to follow Tcl's syntax for the command,  which
              may stretch across multiple logical lines. The command will be run in a save interpreter.

       [4]    A  (logical)  line  starting  with  the word "set" (modulo whitespace) is interpreted as Tcl's set
              command and executed as such. I.e. this command has to follow Tcl's syntax for the command,  which
              may stretch across multiple logical lines. The command will be run in a save interpreter.

       [5]    A  line  of  the form "platform variable value" defines a platform specific configuration variable
              and value.  The variable has to be the name of one of the configuration  keys  listed  earlier  in
              this  section,  and  the  platform string identifies the platform the setting is for. All settings
              with the same identification string form the configuration block for this platform.

       [6]    A line of the special form "platform when expression" marks the platform and all the  settings  in
              its configuration block as conditional on the expression.

              If  the  build  platform  is  not a prefix of platform, nor vice versa the whole block is ignored.
              Otherwise the expression is evaluated via expr, in the same safe interpreter used to run  any  set
              and if commands found in the configuration file (see above).

              If  the  expression  evaluates  to  true  this  configuration  block is considered to be the build
              platform fo the host and chosen as the default configuration.  An large example of of this feature
              is  the  handling  of  OS  X  found  in  the  standard  configuration  file,  where it selects the
              architectures to build based on the version of the operating system, the available SDK, etc.  I.e.
              it chooses whether the output is universal or not, and whether it is old-style (ix86 + ppc) versus
              new-style (ix86 32+64) of universality.

       [7]    A line of the special form "platform copy sourceplatform" copies the configuration  variables  and
              values  currently  defined  in  the  configuration  block  for sourceplatform to that of platform,
              overwriting existing values, and creating missing ones. Variables of platform not  defined  by  by
              sourceplatform are not touched.

              The copied values can be overridden later in the configuration file. Multiple copy lines may exist
              for a platform and be intermixed with normal configuration definitions. Only the  last  definition
              of a variable is used.

       [8]    At last, a line of the form "variable value" defines a default configuration variable and value.

   STUBS TABLES This section is for developers of extensions not based on critcl, yet
       also wishing to interface with stubs as they are understood and used by critcl, either by exporting their
       own stubs table to a critcl-based extension, or importing a stubs table of a critcl-based extension  into
       their own.

       To this end we describe the stubs table information of a package foo.

       [1]    Note that the differences in the capitalization of "foo", "Foo", "FOO", etc. below demonstrate how
              to capitalize the actual package name in each context.

       [2]    All relevant files must be available in a sub-directory "foo" which can be found  on  the  include
              search paths.

       [3]    The  above  directory  may  contain  a  file  "foo.decls". If present it is assumed to contain the
              external representation of the stubs table the headers mentioned in the following items are  based
              on.

              critcl  is  able  to  use  such  a  file  to give the importing package programmatic access to the
              imported API, for automatic code generation and the like.

       [4]    The above directory must contain a header file "fooDecls.h". This file declares the exported  API.
              It  is used by both exporting and importing packages. It is usually generated and must contain (in
              the order specified):

              [1]    the declarations of the exported, i.e. public, functions of foo,

              [2]    the declaration of structure "FooStubs" for the stub table,

              [3]    the C preprocessor macros which route the invocations of the public functions  through  the
                     stubs table.

                     These  macros  must  be  defined if, and only if, the C preprocessor macro USE_FOO_STUBS is
                     defined. Package foo does not define this macro, as it  is  allowed  to  use  the  exported
                     functions  directly.  All importing packages however must define this macro, to ensure that
                     they do not use any of the exported functions directly, but only through the stubs table.

              [4]    If the exported functions need additional types for their  proper  declaration  then  these
                     types should be put into a separate header file (of arbitrary name) and "fooDecls.h" should
                     contain an #include directive to this header at the top.

       A very reduced, yet also complete example, from a package for low-level random number generator functions
       can be found at the end of this section.

       [5]    The above directory must contain a header file "fooStubLib.h". This file defines everything needed
              to use the API of foo. Consequently it is used only by importing packages. It is usually generated
              and must contain (in the order specified):

              [1]    An #include directive for "tcl.h", with USE_TCL_STUBS surely defined.

              [2]    An #include directive for "fooDecls.h", with USE_FOO_STUBS surely defined.

              [3]    A definition of the stubs table variable, i.e.

                     const FooStubs* fooStubsPtr;

              [4]    A definition of the stubs initializer function, like

                     char *
                     Foo_InitStubs(Tcl_Interp *interp, CONST char *version, int exact)
                     {
                         /*
                          * Boiler plate C code initalizing the stubs table variable,
                          * i.e. "fooStubsPtr".
                          */

                         CONST char *actualVersion;

                         actualVersion = Tcl_PkgRequireEx(interp, "foo", version,
                                    exact, (ClientData *) &fooStubsPtr);

                         if (!actualVersion) {
                       return NULL;
                         }

                         if (!fooStubsPtr) {
                       Tcl_SetResult(interp,
                                "This implementation of Foo does not support stubs",
                                TCL_STATIC);
                       return NULL;
                         }

                         return (char*) actualVersion;
                     }

              This  header  file must be included by an importing package exactly once, so that it contains only
              one definition of both stubs table and stubs initializer function.

              The importing package's initialization function must further contain a statement like

              if (!Foo_InitStubs (ip, "1", 0)) {
                  return TCL_ERROR;
              }

              which invokes foo's stubs initializer function to set the local stub table up.

              For a complete example of such a header file see below, at the end of this section.

       [6]    The last item above, about "fooStubLib.h" differs from the regular stub stable system used by Tcl.
              The  regular system assumes that a static library "libfoostub.a" was installed by package foo, and
              links it.

              IMVHO critcl's approach is simpler, using only header files found in a single location, vs. header
              files and static library found in multiple, different locations.

              A  second simplification is that we avoid having to extend critcl's compiler backend with settings
              for the creation of static libraries.

       Below is a complete set of example header files, reduced, yet still complete, from  a  package  for  low-
       level random number generator functions:

       "rngDecls.h":

              #ifndef rng_DECLS_H
              #define rng_DECLS_H

              #include <tcl.h>

              /*
               * Exported function declarations:
               */

              /* 0 */
              EXTERN void rng_bernoulli(double p, int*v);

              typedef struct RngStubs {
                  int magic;
                  const struct RngStubHooks *hooks;

                  void (*rng_bernoulli) (double p, int*v); /* 0 */
              } RngStubs;

              #ifdef __cplusplus
              extern "C" {
              #endif
              extern const RngStubs *rngStubsPtr;
              #ifdef __cplusplus
              }
              #endif

              #if defined(USE_RNG_STUBS)

              /*
               * Inline function declarations:
               */

              #define rng_bernoulli  (rngStubsPtr->rng_bernoulli) /* 0 */

              #endif /* defined(USE_RNG_STUBS) */
              #endif /* rng_DECLS_H */

       "rngStubLib.h":

              /*
               * rngStubLib.c --
               *
               * Stub object that will be statically linked into extensions that wish
               * to access rng.
               */

              #ifndef USE_TCL_STUBS
              #define USE_TCL_STUBS
              #endif
              #undef  USE_TCL_STUB_PROCS

              #include <tcl.h>

              #ifndef USE_RNG_STUBS
              #define USE_RNG_STUBS
              #endif
              #undef  USE_RNG_STUB_PROCS

              #include "rngDecls.h"

              /*
               * Ensure that Rng_InitStubs is built as an exported symbol.  The other stub
               * functions should be built as non-exported symbols.
               */

              #undef  TCL_STORAGE_CLASS
              #define TCL_STORAGE_CLASS DLLEXPORT

              const RngStubs* rngStubsPtr;

              /*
               *----------------------------------------------------------------------
               *
               * Rng_InitStubs --
               *
               * Checks that the correct version of Rng is loaded and that it
               * supports stubs. It then initialises the stub table pointers.
               *
               * Results:
               *  The actual version of Rng that satisfies the request, or
               *  NULL to indicate that an error occurred.
               *
               * Side effects:
               *  Sets the stub table pointers.
               *
               *----------------------------------------------------------------------
               */

              #ifdef Rng_InitStubs
              #undef Rng_InitStubs
              #endif

              char *
              Rng_InitStubs(Tcl_Interp *interp, CONST char *version, int exact)
              {
                  CONST char *actualVersion;

                  actualVersion = Tcl_PkgRequireEx(interp, "rng", version,
                             exact, (ClientData *) &rngStubsPtr);
                  if (!actualVersion) {
                return NULL;
                  }

                  if (!rngStubsPtr) {
                Tcl_SetResult(interp,
                         "This implementation of Rng does not support stubs",
                         TCL_STATIC);
                return NULL;
                  }

                  return (char*) actualVersion;
              }

EXAMPLES

       See section "Embedding C" in Using CriTcl.

AUTHORS

       Jean Claude Wippler, Steve Landers, Andreas Kupries

BUGS, IDEAS, FEEDBACK

       This  document,  and  the package it describes, will undoubtedly contain bugs and other problems.  Please
       report them at https://github.com/andreas-kupries/critcl/issues.  Ideas for enhancements you may have for
       either  package,  application,  and/or  the documentation are also very welcome and should be reported at
       https://github.com/andreas-kupries/critcl/issues as well.

KEYWORDS

       C code, Embedded C Code, calling C code from Tcl, code generator, compile & run, compiler,  dynamic  code
       generation, dynamic compilation, generate package, linker, on demand compilation, on-the-fly compilation

CATEGORY

       Glueing/Embedded C code

       Copyright (c) Jean-Claude Wippler
       Copyright (c) Steve Landers
       Copyright (c) 2011-2024 Andreas Kupries