SWIG Users Guide	Extending SWIG	272

As for making modifications to SWIG, all files in the “SWIG” directory should be considered “critical.” Making changes here can cause serious problems in all SWIG language modules. When making customizations, one should only consider files in the “Modules” directory if at all possible.

The organization of this chapter

The remainder of this chapter is a bottom-up approach is to building SWIG modules. It will start with the basics and gradually build up a working language module, introducing new concepts as needed.

Compiling a SWIG extension

The first order of business is that of compiling an extension to SWIG and using it. This is the easy part.

Required files

To build any SWIG extension you need to locate the files “swig.h” and “libswig.a”. In a typical installation, these will usually be found in /usr/local/include and /usr/local/lib respectively. All extension modules will need to include the “swig.h” header file and link against the libswig.a library.

Required C++ compiler

Due to name-mangling in the C++ compiler (which is different between compiler implementations), you will need to use the same C++ compiler used to compile SWIG. If you don’t know which C++ compiler was used, typing ‘swig -version’ will cause SWIG to print out its version number and the C++ compiler that was used to build it.

Writing a main program

To get any extension to work, it is necessary to write a small main() program to create a language object and start the SWIG parser. For example :

#include	<swig.h>
#include	“swigtcl.h”	// Language specific header

extern int SWIG_main(int, char **, Language *, Documentation *); int main(int argc, char **argv) {

TCL *l = new Tcl;	// Create a new Language object
init_args(argc, argv);	// Initialize args
return SWIG_main(argc, argv, l, 0);

}

Compiling

To compile your extension, do the following :

% c++ tcl.cxx main.cxx -lswig -o myswig

In this case we get a special version of SWIG that compiles Tcl extensions.

Version 1.1, June 24, 1997