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Author image Mattia Barbon


ExtUtils::XSpp - XS for C++


  xspp [--typemap=typemap.xsp [--typemap=typemap2.xsp]]
       [--xsubpp[=/path/to/xsubpp] [--xsubpp-args="xsubpp args"]


  perl -MExtUtils::XSpp::Cmd -e xspp -- <xspp options and arguments>

In Foo.xs

  INCLUDE_COMMAND: $^X -MExtUtils::XSpp::Cmd -e xspp -- <xspp options/arguments>

Using ExtUtils::XSpp::Cmd is equivalent to using the xspp command line script, except that there is no guarantee for xspp to be installed in the system PATH.


XS++ is just a thin layer over plain XS, hence to use it you are supposed to know, at the very least, C++ and XS.

This means that you will need typemaps for both the normal XS pre-processor xsubpp and the XS++ pre-processor xspp.



Can be specified multiple times to process additional typemap files before the main XS++ input files. Typemap files are processed the same way as regular XS++ files, except that output code is discarded.


If specified, XS++ will run xsubpp after processing the XS++ input file. If the path to xsubpp is not specified, xspp expects to find it in the system PATH.

--xsubpp-args="extra xsubpp args"

Can be used to pass additional command line arguments to xsubpp.


There is nothing special about typemap files (i.e. you can put typemaps directly in your .xsp file), but it is handy to have common typemaps in a separate file, to avoid duplication.

  %typemap{<C++ type>}{simple};

Just let XS++ know that this is a valid type, the type will be passed unchanged to XS code except that any const qualifiers will be stripped.

  %typemap{<C++ reference type>}{reference};

Handle C++ references: the XS variable will be declared as a pointer, and it will be explicitly dereferenced in the function call. If it is used in the return value, the function will create copy of the returned value using a copy constructor.

As a shortcut for the common case of declaring both of the above for a given type, you may use

  %typemap{<C++ type>};

Which has the same effect as:

  %typemap{<C++ type>}{simple};
  %typemap{<C++ type>&}{reference};

For more control over the type mapping, you can use the parsed variant as follows.

  %typemap{<C++ type 1>}{parsed}{%<C++ type 2>%};

When C++ type 1 is used, replace it with C++ type 2 in the generated XS code.

  %typemap{<C++ type>}{parsed}{
      %cpp_type{%<C++ type 2>%};
      %call_function_code{% $CVar = new Foo( $Call ) %};
      %cleanup_code{% ... %};
      %precall_code{% ... %};

      # use only one of the following
      %output_code{% $PerlVar = newSViv( $CVar ) %};
      %output_list{% PUTBACK; XPUSHi( $CVar ); SPAGAIN %};

Is a more flexible form for the parsed typemap. All the parameters are optional.


Specifies the C++ type used for the variable declaration in the generated XS code.

If not specified defaults to the type specified in the typemap.


Used when the typemap applies to the return value of the function.

Specifies the code to use in the function call. The special variables $Call and $CVar are replaced with the actual call code and the name of the C++ return variable.


Used when the typemap applies to the return value of the function. See also %output_list.

Specifies the code emitted right after the function call to convert the C++ return value into a Perl return value. The special variable $CVar is replaced with the C++ return variable name.


Used when the typemap applies to the return value of the function.

Specifies some code emitted after output value processing. The special variables $PerlVar and $CVar are replaced with the names of the C++ variables containing the Perl scalar and the corresponding C++ value.


Used when the typemap applies to a parameter.

Specifies some code emitted after argument processing and before calling the C++ method. The special variables $PerlVar and $CVar are replaced with the names of the C++ variables containing the Perl scalar and the corresponding C++ value.


Used when the typemap applies to the return value of the function, as an alternative to %output_code.

Specifies some code that manipulates the Perl stack directly in order to return a list. The special variable $CVar is replaced with the C++ name of the output variable.

The code must use PUTBACK/SPAGAIN if appropriate.


Anything that does not look like a XS++ directive or a class declaration is passed verbatim to XS. If you want XS++ to ignore code that looks like a XS++ directive or class declaration, simply surround it with a raw block delimiter like this:

  XS++ won't interpret this


See under Classes. Note that custom %code blocks are the only exception to the exception handling. By specifying a custom %code block, you forgo the automatic exception handlers.



By default XS++ output goes to standard output; to change this, use the %file directive; use - for standard output.



Will be used to generate the MODULE=Module::Name XS directives. It indirectly sets the name of the shared library that is generated as well as the name of the module via which XSLoader will be able to find/load it.


  %name{Perl::Class} class MyClass { ... };
  %name{Perl::Func} int foo();

Specifies the Perl name under which the C++ class/function will be accessible. By default, constructor names are mapped to new in Perl.


See TYPEMAPS above.


When you need to pass a string from Perl to an XSUB that takes the C string and its length as arguments, you may have XS++ pass the length of the string automatically. For example, if you declare a method as follows,

  void PrintLine( char* line, unsigned int %length{line} );

you can call the method from Perl like this:

  $object->PrintLine( $string );

This feature is also present in plain XS. See also: perlxs.

If you use %length(line) in conjunction with any kind of special code block such as %code, %postcall, etc., then you can refer to the length of the string (here: line) efficiently as length(line) in the code.


  %name{My::Class} class MyClass : public %name{My::Base} MyBase
      // can be called in Perl as My::Class->new( ... );
      MyClass( int arg );
      // My::Class->newMyClass( ... );
      %name{newMyClass} MyClass( const char* str, int arg );

      // standard DESTROY method

      int GetInt();
      void SetValue( int arg = -1 );

      %name{SetString} void SetValue( const char* string = NULL );

      // Supply a C<CODE:> or C<CLEANUP:> block for the XS
      int MyMethod( int a, int b )
          %code{% RETVAL = a + b; %}
          %cleanup{% /* do something */ %};


XS++ recognizes both C-style comments /* ... */ and C++-style comments // .... Comments are removed from the XS output.


C++ Exceptions are always caught and transformed to Perl croak() calls. If the exception that was caught inherited from std::exception, then the what() message is included in the Perl-level error message. All other exceptions will result in the croak() message "Caught unhandled C++ exception of unknown type".

Note that if you supply a custom %code block for a function or method, the automatic exception handling is turned off.


The distribution contains an examples directory. The examples/XSpp-Example directory therein demonstrates a particularly simple way of getting started with XS++.


Mattia Barbon <mbarbon@cpan.org>


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