1 Preface

1.1 Introduction

SWIG (Simplified Wrapper and Interface Generator) is a software development tool for building scripting language interfaces to C and C++ programs. Originally developed in 1995, SWIG was first used by scientists in the Theoretical Physics Division at Los Alamos National Laboratory for building user interfaces to simulation codes running on the Connection Machine 5 supercomputer. In this environment, scientists needed to work with huge amounts of simulation data, complex hardware, and a constantly changing code base. The use of a scripting language interface provided a simple yet highly flexible foundation for solving these types of problems. SWIG simplifies development by largely automating the task of scripting language integration--allowing developers and users to focus on more important problems.

Although SWIG was originally developed for scientific applications, it has since evolved into a general purpose tool that is used in a wide variety of applications--in fact almost anything where C/C++ programming is involved.

1.2 Special Introduction for Version 1.3

Since SWIG was released in 1996, its user base and applicability has continued to grow. Although its rate of development has varied, an active development effort has continued to make improvements to the system. Today, nearly a dozen developers are working to create SWIG-2.0---a system that aims to provide wrapping support for nearly all of the ANSI C++ standard and approximately ten target languages including Guile, Java, Mzscheme, Ocaml, Perl, Pike, PHP, Python, Ruby, and Tcl.

1.3 SWIG Versions

For several years, the most stable version of SWIG has been release 1.1p5. Starting with version 1.3, a new version numbering scheme has been adopted. Odd version numbers (1.3, 1.5, etc.) represent development versions of SWIG. Even version numbers (1.4, 1.6, etc.) represent stable releases. Currently, developers are working to create a stable SWIG-2.0 release. Don't let the development status of SWIG-1.3 scare you---it is much more stable (and capable) than SWIG-1.1p5.

1.4 SWIG resources

The official location of SWIG related material is


This site contains the latest version of the software, users guide, and information regarding bugs, installation problems, and implementation tricks.

You can also subscribe to the swig-user mailing list by visiting the page


The mailing list often discusses some of the more technical aspects of SWIG along with information about beta releases and future work.

CVS access to the latest version of SWIG is also available. More information about this can be obtained at:


1.5 Prerequisites

This manual assumes that you know how to write C/C++ programs and that you have at least heard of scripting languages such as Tcl, Python, and Perl. A detailed knowledge of these scripting languages is not required although some familiarity won't hurt. No prior experience with building C extensions to these languages is required---after all, this is what SWIG does automatically. However, you should be reasonably familiar with the use of compilers, linkers, and makefiles since making scripting language extensions is somewhat more complicated than writing a normal C program.

Recent SWIG releases have become significantly more capable in their C++ handling--especially support for advanced features like namespaces, overloaded operators, and templates. Whenever possible, this manual tries to cover the technicalities of this interface. However, this isn't meant to be a tutorial on C++ programming. For many of the gory details, you will almost certainly want to consult a good C++ reference. If you don't program in C++, you may just want to skip those parts of the manual.

1.6 Organization of this manual

The first few chapters of this manual describe SWIG in general and provide an overview of its capabilities. The remaining chapters are devoted to specific SWIG language modules and are self contained. Thus, if you are using SWIG to build Python interfaces, you can probably skip to that chapter and find almost everything you need to know. Caveat: we are currently working on a documentation rewrite and many of the older language module chapters are still somewhat out of date.

1.7 How to avoid reading the manual

If you hate reading manuals, glance at the "Introduction" which contains a few simple examples. These examples contain about 95% of everything you need to know to use SWIG. After that, simply use the language-specific chapters as a reference. The SWIG distribution also comes with a large directory of examples that illustrate different topics.

1.8 Backwards Compatibility

If you are a previous user of SWIG, don't expect recent versions of SWIG to provide backwards compatibility. In fact, backwards compatibility issues may arise even between successive 1.3.x releases. Although these incompatibilities are regrettable, SWIG-1.3 is an active development project. The primary goal of this effort is to make SWIG better---a process that would simply be impossible if the developers are constantly bogged down with backwards compatibility issues.

On a positive note, a few incompatibilities are a small price to pay for the large number of new features that have been added---namespaces, templates, smart pointers, overloaded methods, operators, and more.

If you need to work with different versions of SWIG and backwards compatibility is an issue, you can use the SWIG_VERSION preprocessor symbol which holds the version of SWIG being executed. SWIG_VERSION is a hexadecimal integer such as 0x010311 (corresponding to SWIG-1.3.11). This can be used in an interface file to define different typemaps, take advantage of different features etc:

#if SWIG_VERSION >= 0x010311
/* Use some fancy new feature */

Note: The version symbol is not defined in the generated SWIG wrapper file. The SWIG preprocessor has defined SWIG_VERSION since SWIG-1.3.11.

1.9 Credits

SWIG is an unfunded project that would not be possible without the contributions of many people. Most recent SWIG development has been supported by Matthias Köppe, William Fulton, Lyle Johnson, Richard Palmer, Thien-Thi Nguyen, Jason Stewart, Loic Dachary, Masaki Fukushima, Luigi Ballabio, Sam Liddicott, Art Yerkes, Marcelo Matus, Harco de Hilster, John Lenz, and Surendra Singhi.

Historically, the following people contributed to early versions of SWIG. Peter Lomdahl, Brad Holian, Shujia Zhou, Niels Jensen, and Tim Germann at Los Alamos National Laboratory were the first users. Patrick Tullmann at the University of Utah suggested the idea of automatic documentation generation. John Schmidt and Kurtis Bleeker at the University of Utah tested out the early versions. Chris Johnson supported SWIG's developed at the University of Utah. John Buckman, Larry Virden, and Tom Schwaller provided valuable input on the first releases and improving the portability of SWIG. David Fletcher and Gary Holt have provided a great deal of input on improving SWIG's Perl5 implementation. Kevin Butler contributed the first Windows NT port.

1.10 Bug reports

Although every attempt has been made to make SWIG bug-free, we are also trying to make feature improvements that may introduce bugs. To report a bug, either send mail to the SWIG developer list at the swig-devel mailing list or report a bug at the SWIG bug tracker. In your report, be as specific as possible, including (if applicable), error messages, tracebacks (if a core dump occurred), corresponding portions of the SWIG interface file used, and any important pieces of the SWIG generated wrapper code. We can only fix bugs if we know about them.