Inline::C - C Language Support for Inline


    This document describes Inline::C version 0.82.


    Inline::C is a module that allows you to write Perl subroutines in C.
    Since version 0.30 the Inline module supports multiple programming
    languages and each language has its own support module. This document
    describes how to use Inline with the C programming language. It also
    goes a bit into Perl C internals.

    If you want to start working with programming examples right away,
    check out Inline::C::Cookbook. For more information on Inline in
    general, see Inline.


    You never actually use Inline::C directly. It is just a support module
    for using with C. So the usage is always:

        use Inline C => ...;


        bind Inline C => ...;


    The Inline grammar for C recognizes certain function definitions (or
    signatures) in your C code. If a signature is recognized by Inline,
    then it will be available in Perl-space. That is, Inline will generate
    the "glue" necessary to call that function as if it were a Perl
    subroutine. If the signature is not recognized, Inline will simply
    ignore it, with no complaints. It will not be available from
    Perl-space, although it will be available from C-space.

    Inline looks for ANSI/prototype style function definitions. They must
    be of the form:

        return-type function-name ( type-name-pairs ) { ... }

    The most common types are: int, long, double, char*, and SV*. But you
    can use any type for which Inline can find a typemap. Inline uses the
    typemap file distributed with Perl as the default. You can specify more
    typemaps with the typemaps configuration option.

    A return type of void may also be used. The following are examples of
    valid function definitions.

        int Foo(double num, char* str) {
        void Foo(double num, char* str) {
        void Foo(SV*, ...) {
        long Foo(int i, int j, ...) {
        SV* Foo(void) { # 'void' arg invalid with the ParseRecDescent parser.
                        # Works only with the ParseRegExp parser.
                        # See the section on `using` (below).
        SV* Foo() {  # Alternative to specifying 'void' arg. Is valid with
                     # both the ParseRecDescent and ParseRegExp parsers.

    The following definitions would not be recognized:

        Foo(int i) {               # no return type
        int Foo(float f) {         # no (default) typemap for float
        int Foo(num, str) double num; char* str; {

    Notice that Inline only looks for function definitions, not function
    prototypes. Definitions are the syntax directly preceding a function
    body. Also Inline does not scan external files, like headers. Only the
    code passed to Inline is used to create bindings; although other
    libraries can linked in, and called from C-space.


    For information on how to specify Inline configuration options, see
    Inline. This section describes each of the configuration options
    available for C. Most of the options correspond either to MakeMaker or
    XS options of the same name. See ExtUtils::MakeMaker and perlxs.


      Specifies extra statements to automatically included. They will be
      added onto the defaults. A newline char will be automatically added.

          use Inline C => config => auto_include => '#include "yourheader.h"';


      If you enable => autowrap, Inline::C will parse function declarations
      (prototype statements) in your C code. For each declaration it can
      bind to, it will create a dummy wrapper that will call the real
      function which may be in an external library. This is a nice
      convenience for functions that would otherwise just require an empty
      wrapper function.

      This is similar to the base functionality you get from h2xs. It can
      be very useful for binding to external libraries.


      Specifies C code to be executed in the XS BOOT section. Corresponds
      to the XS parameter.


      Specify which compiler to use.


      Specify compiler flags - same as ExtUtils::MakeMaker's CCFLAGS
      option. Whatever gets specified here replaces the default
      $Config{ccflags}. Often, you'll want to add an extra flag or two
      without clobbering the default flags in which case you could instead
      use ccflagsex (see below) or, if has already been loaded:

          use Inline C => Config => ccflags => $Config{ccflags} . " -DXTRA -DTOO";


      Extend compiler flags. Sets CCFLAGS to $Config{ccflags} followed by a
      space, followed by the specified value:

          use Inline C => config => ccflagsex => "-DXTRA -DTOO";


    Specify preprocessor flags. Passed to cpp C preprocessor by
    Preprocess() in Inline::Filters.

        use Inline C => <<'END',
            FILTERS => 'Preprocess';
        use Inline C => <<'END',
            CPPFLAGS => ' -DPREPROCESSOR_DEFINE=4321',
            FILTERS => 'Preprocess';


      Allows you to specify a list of source code filters. If more than one
      is requested, be sure to group them with an array ref. The filters
      can either be subroutine references or names of filters provided by
      the supplementary Inline::Filters module.

      Your source code will be filtered just before it is parsed by Inline.
      The MD5 fingerprint is generated before filtering. Source code
      filters can be used to do things like stripping out POD
      documentation, pre-expanding #include statements or whatever else you
      please. For example:

          use Inline C => DATA =>
                     filters => [Strip_POD => \&MyFilter => Preprocess ];

      Filters are invoked in the order specified. See Inline::Filters for
      more information.

      If a filter is an array reference, it is assumed to be a usage of a
      filter plug- in named by the first element of that array reference.
      The rest of the elements of the array reference are used as arguments
      to the filter. For example, consider a filters parameter like this:

          use Inline C => DATA => filters => [ [ Ragel => '-G2' ] ];

      In order for Inline::C to process this filter, it will attempt to
      require the module Inline::Filters::Ragel and will then call the
      filter function in that package with the argument '-G2'. This
      function will return the actual filtering function.


      Specifies an include path to use. Corresponds to the MakeMaker
      parameter. Expects a fully qualified path.

          use Inline C => config => inc => '-I/inc/path';


      Specify which linker to use.


      Specify which linker flags to use.

      NOTE: These flags will completely override the existing flags,
      instead of just adding to them. So if you need to use those too, you
      must respecify them here.


      Specifies external libraries that should be linked into your code.
      Corresponds to the MakeMaker parameter. Provide a fully qualified
      path with the -L switch if the library is in a location where it
      won't be found automatically.

          use Inline C => config => libs => '-lyourlib';


          use Inline C => config => libs => '-L/your/path -lyourlib';


      Specify the name of the 'make' utility to use.


      Specifies a user compiled object that should be linked in.
      Corresponds to the MakeMaker parameter. Expects a fully qualified

          use Inline C => config => myextlib => '/your/path/';


      This controls the MakeMaker OPTIMIZE setting. By setting this value
      to '-g', you can turn on debugging support for your Inline
      extensions. This will allow you to be able to set breakpoints in your
      C code using a debugger like gdb.


      Specifies a prefix that will be automatically stripped from C
      functions when they are bound to Perl. Useful for creating wrappers
      for shared library API-s, and binding to the original names in Perl.
      Also useful when names conflict with Perl internals. Corresponds to
      the XS parameter.

          use Inline C => config => prefix => 'ZLIB_';


      Specifies code that will precede the inclusion of all files specified
      in auto_include (ie EXTERN.h, perl.h, XSUB.h, INLINE.h and anything
      else that might have been added to auto_include by the user). If the
      specified value identifies a file, the contents of that file will be
      inserted, otherwise the specified value is inserted.

          use Inline C => config => pre_head => $code_or_filename;


      Corresponds to the XS keyword 'PROTOTYPE'. See the perlxs
      documentation for both 'PROTOTYPES' and 'PROTOTYPE'. As an example,
      the following will set the PROTOTYPE of the 'foo' function to '$',
      and disable prototyping for the 'bar' function.

          use Inline C => config => prototype => {foo => '$', bar => 'DISABLE'}


      Corresponds to the XS keyword 'PROTOTYPES'. Can take only values of
      'ENABLE' or 'DISABLE'. (Contrary to XS, default value is 'DISABLE').
      See the perlxs documentation for both 'PROTOTYPES' and 'PROTOTYPE'.

          use Inline C => config => prototypes => 'ENABLE';


      Specifies extra typemap files to use. These types will modify the
      behaviour of the C parsing. Corresponds to the MakeMaker parameter.
      Specify either a fully qualified path or a path relative to the cwd
      (ie relative to what the cwd is at the time the script is loaded).

          use Inline C => config => typemaps => '/your/path/typemap';


      Specifies which parser to use. The default is
      Inline::C::Parser::RecDescent, which uses the Parse::RecDescent

      The other options are ::Parser::Pegex and ::Parser::RegExp, which
      uses the Inline::C::Parser::Pegex and Inline::C::Parser::RegExp
      modules that ship with Inline::C.

          use Inline C => config => using => '::Parser::Pegex';

      Note that the following old options are deprecated, but still work at
      this time:

	* ParseRecDescent

	* ParseRegExp

	* ParsePegex


    This section describes how the Perl variables get mapped to C variables
    and back again.

    First, you need to know how Perl passes arguments back and forth to
    subroutines. Basically it uses a stack (also known as the Stack). When
    a sub is called, all of the parenthesized arguments get expanded into a
    list of scalars and pushed onto the Stack. The subroutine then pops all
    of its parameters off of the Stack. When the sub is done, it pushes all
    of its return values back onto the Stack.

    The Stack is an array of scalars known internally as SV's. The Stack is
    actually an array of pointers to SV or SV*; therefore every element of
    the Stack is natively a SV*. For FMTYEWTK about this, read perldoc

    So back to variable mapping. XS uses a thing known as "typemaps" to
    turn each SV* into a C type and back again. This is done through
    various XS macro calls, casts and the Perl API. See perldoc perlapi. XS
    allows you to define your own typemaps as well for fancier non-standard
    types such as typedef- ed structs.

    Inline uses the default Perl typemap file for its default types. This
    file is called /usr/local/lib/perl5/5.6.1/ExtUtils/typemap, or
    something similar, depending on your Perl installation. It has
    definitions for over 40 types, which are automatically used by Inline.
    (You should probably browse this file at least once, just to get an
    idea of the possibilities.)

    Inline parses your code for these types and generates the XS code to
    map them. The most commonly used types are:

      * int

      * long

      * double

      * char*

      * void

      * SV*

    If you need to deal with a type that is not in the defaults, just use
    the generic SV* type in the function definition. Then inside your code,
    do the mapping yourself. Alternatively, you can create your own typemap
    files and specify them using the typemaps configuration option.

    A return type of void has a special meaning to Inline. It means that
    you plan to push the values back onto the Stack yourself. This is what
    you need to do to return a list of values. If you really don't want to
    return anything (the traditional meaning of void) then simply don't
    push anything back.

    If ellipsis or ... is used at the end of an argument list, it means
    that any number of SV*s may follow. Again you will need to pop the
    values off of the Stack yourself.

    See "EXAMPLES" below.


    When you write Inline C, the following lines are automatically
    prepended to your code (by default):

        #include "EXTERN.h"
        #include "perl.h"
        #include "XSUB.h"
        #include "INLINE.h"

    The file INLINE.h defines a set of macros that are useful for handling
    the Perl Stack from your C functions.


      You'll need to use this one, if you want to use the others. It sets
      up a few local variables: sp, items, ax and mark, for use by the
      other macros. It's not important to know what they do, but I mention
      them to avoid possible name conflicts.

      NOTE: Since this macro declares variables, you'll need to put it with
      your other variable declarations at the top of your function. It must
      come before any executable statements and before any other
      Inline_Stack macros.


      Returns the number of arguments passed in on the Stack.


      Refers to a particular SV* in the Stack, where i is an index number
      starting from zero. Can be used to get or set the value.


      Use this before pushing anything back onto the Stack. It resets the
      internal Stack pointer to the beginning of the Stack.


      Push a return value back onto the Stack. The value must be of type


      After you have pushed all of your return values, you must call this


      Return n items on the Stack.


      A special macro to indicate that you really don't want to return
      anything. Same as:


      Please note that this macro actually returns from your function.

    Each of these macros is available in 3 different styles to suit your
    coding tastes. The following macros are equivalent.


    All of this functionality is available through XS macro calls as well.
    So why duplicate the functionality? There are a few reasons why I
    decided to offer this set of macros. First, as a convenient way to
    access the Stack. Second, for consistent, self documenting, non-cryptic
    coding. Third, for future compatibility. It occurred to me that if a
    lot of people started using XS macros for their C code, the interface
    might break under Perl6. By using this set, hopefully I will be able to
    insure future compatibility of argument handling.

    Of course, if you use the rest of the Perl API, your code will most
    likely break under Perl6. So this is not a 100% guarantee. But since
    argument handling is the most common interface you're likely to use, it
    seemed like a wise thing to do.


    The definitions of your C functions will fall into one of the following
    four categories. For each category there are special considerations.

    int Foo(int arg1, char* arg2, SV* arg3) {

      This is the simplest case. You have a non void return type and a
      fixed length argument list. You don't need to worry about much. All
      the conversions will happen automatically.

    void Foo(int arg1, char* arg2, SV* arg3) {

      In this category you have a void return type. This means that either
      you want to return nothing, or that you want to return a list. In the
      latter case you'll need to push values onto the Stack yourself. There
      are a few Inline macros that make this easy. Code something like

          int i, max; SV* my_sv[10];
          for (i = 0; i < max; i++)

      After resetting the Stack pointer, this code pushes a series of
      return values. At the end it uses Inline_Stack_Done to mark the end
      of the return stack.

      If you really want to return nothing, then don't use the
      Inline_Stack_ macros. If you must use them, then set use
      Inline_Stack_Void at the end of your function.

    char* Foo(SV* arg1, ...) {

      In this category you have an unfixed number of arguments. This means
      that you'll have to pop values off the Stack yourself. Do it like

          int i;
          for (i = 0; i < Inline_Stack_Items; i++)

      The return type of Inline_Stack_Item(i) is SV*.

    void* Foo(SV* arg1, ...) {

      In this category you have both a void return type and an unfixed
      number of arguments. Just combine the techniques from Categories 3
      and 4.


    Here are a few examples. Each one is a complete program that you can
    try running yourself. For many more examples see Inline::C::Cookbook.

 Example #1 - Greetings

    This example will take one string argument (a name) and print a
    greeting. The function is called with a string and with a number. In
    the second case the number is forced to a string.

    Notice that you do not need to #include <stdio.h>. The perl.h header
    file which gets included by default, automatically loads the standard C
    header files for you.

        use Inline 'C';
        void greet(char* name) {
          printf("Hello %s!\n", name);

 Example #2 - and Salutations

    This is similar to the last example except that the name is passed in
    as a SV* (pointer to Scalar Value) rather than a string (char*). That
    means we need to convert the SV to a string ourselves. This is
    accomplished using the SvPVX function which is part of the Perl
    internal API. See perldocperlapi for more info.

    One problem is that SvPVX doesn't automatically convert strings to
    numbers, so we get a little surprise when we try to greet 42. The
    program segfaults, a common occurrence when delving into the guts of

        use Inline 'C';
        void greet(SV* sv_name) {
          printf("Hello %s!\n", SvPVX(sv_name));

 Example #3 - Fixing the problem

    We can fix the problem in Example #2 by using the SvPV function
    instead. This function will stringify the SV if it does not contain a
    string. SvPV returns the length of the string as it's second parameter.
    Since we don't care about the length, we can just put PL_na there,
    which is a special variable designed for that purpose.

        use Inline 'C';
        void greet(SV* sv_name) {
          printf("Hello %s!\n", SvPV(sv_name, PL_na));


    For general information about Inline see Inline.

    For sample programs using Inline with C see Inline::C::Cookbook.

    For information on supported languages and platforms see

    For information on writing your own Inline Language Support Module, see

    Inline's mailing list is

    To subscribe, send email to


    If you use C function names that happen to be used internally by Perl,
    you will get a load error at run time. There is currently no
    functionality to prevent this or to warn you. For now, a list of Perl's
    internal symbols is packaged in the Inline module distribution under
    the filename 'symbols.perl'. Avoid using these in your code.


    Ingy döt Net <>

    Sisyphus <>


    Copyright 2000-2022. Ingy döt Net.

    Copyright 2008, 2010-2014. Sisyphus.

    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.