3 Getting started on Windows

This chapter describes SWIG usage on Microsoft Windows. Installing SWIG and running the examples is covered as well as building the SWIG executable. Usage within the Unix like environments MinGW and Cygwin is also detailed.

3.1 Installation on Windows

SWIG does not come with the usual Windows type installation program, however it is quite easy to get started. The main steps are:

3.1.1 Windows Executable

The swigwin distribution contains the SWIG Windows 32-bit executable, swig.exe, which will run on both 32-bit and 64-bit versions of Windows. If you want to build your own swig.exe have a look at Building swig.exe on Windows.

3.2 SWIG Windows Examples

Microsoft Visual C++ is the most commonly used compiler for compiling and linking SWIG's output on Windows. The Examples directory has a few Visual C++ project files (.dsp files). These were produced by Visual C++ 6. Newer versions of Visual Studio are able to open and convert these project files. Each C# example comes with a Visual Studio 2005 solution and associated project files instead of Visual C++ 6 project files. The project files have been set up to execute SWIG in a custom build rule for the SWIG interface (.i) file. Alternatively run the examples using Cygwin.

More information on each of the examples is available with the examples distributed with SWIG (Examples/index.html).

3.2.1 Instructions for using the Examples with Visual Studio

Ensure the SWIG executable is as supplied in the SWIG root directory in order for the examples to work. Most languages require some environment variables to be set before running Visual C++. Note that Visual C++ must be re-started to pick up any changes in environment variables. Open up an example .dsp file, Visual C++ will prompt you to upgrade the project and convert it into an MSBuild project (.vcxproj file) and Solution (.sln file). Note that older versions of Visual C++ will simply create a workspace for you (.dsw file). Ensure the Release build is selected then do a Rebuild Solution from the Build menu. The required environment variables are displayed with their current values during the build.

The list of required environment variables for each module language is also listed below. They are usually set from the Control Panel and System properties, but this depends on which flavour of Windows you are running. If you don't want to use environment variables then change all occurrences of the environment variables in the .dsp files with hard coded values. If you are interested in how the project files are set up there is explanatory information in some of the language module's documentation. C#

The C# examples do not require any environment variables to be set as a C# project file is included. Just open up the .sln solution file in Visual Studio 2005 or later, select Release Build, and do a Rebuild Solution from the Build menu. The accompanying C# and C++ project files are automatically used by the solution file. Java

JAVA_INCLUDE : Set this to the directory containing jni.h
JAVA_BIN : Set this to the bin directory containing javac.exe

Example using JDK1.3:
JAVA_INCLUDE: D:\jdk1.3\include
JAVA_BIN: D:\jdk1.3\bin Perl

PERL5_INCLUDE : Set this to the directory containing perl.h
PERL5_LIB : Set this to the Perl library including path for linking

Example using nsPerl 5.004_04:

PERL5_INCLUDE: D:\nsPerl5.004_04\lib\CORE
PERL5_LIB: D:\nsPerl5.004_04\lib\CORE\perl.lib Python

PYTHON_INCLUDE : Set this to the directory that contains Python.h
PYTHON_LIB : Set this to the Python library including path for linking

Example using Python 2.1.1:
PYTHON_INCLUDE: D:\python21\include
PYTHON_LIB: D:\python21\libs\python21.lib TCL

TCL_INCLUDE : Set this to the directory containing tcl.h
TCL_LIB : Set this to the TCL library including path for linking

Example using ActiveTcl
TCL_INCLUDE: D:\tcl\include
TCL_LIB: D:\tcl\lib\tcl83.lib R

R_INCLUDE : Set this to the directory containing R.h
R_LIB : Set this to the R library (Rdll.lib) including path for linking. The library needs to be built as described in the R README.packages file (the pexports.exe approach is the easiest).

Example using R 2.5.1:
R_INCLUDE: C:\Program Files\R\R-2.5.1\include
R_LIB: C:\Program Files\R\R-2.5.1\bin\Rdll.lib Ruby

RUBY_INCLUDE : Set this to the directory containing ruby.h
RUBY_LIB : Set this to the ruby library including path for linking

Example using Ruby 1.6.4:
RUBY_INCLUDE: D:\ruby\lib\ruby\1.6\i586-mswin32
RUBY_LIB: D:\ruby\lib\mswin32-ruby16.lib

3.2.2 Instructions for using the Examples with other compilers

If you do not have access to Visual C++ you will have to set up project files / Makefiles for your chosen compiler. There is a section in each of the language modules detailing what needs setting up using Visual C++ which may be of some guidance. Alternatively you may want to use Cygwin as described in the following section.

3.3 Building swig.exe on Windows

The SWIG distribution provides a pre-built swig.exe and so it is not necessary for users to build the SWIG executable. However, this section is provided for those that want to modify the SWIG source code in a Windows environment. Normally this is not needed, so most people will want to ignore this section.

There are various ways to build the SWIG executable including CMake which is able to generate project files for building with Visual Studio. SWIG can also be compiled and run using MSYS2, Cygwin or MinGW, all of which provide a Unix like front end to Windows and comes free with the gcc C/C++ compiler.

3.3.1 Building swig.exe using CMake

SWIG can be built using CMake and Visual Studio rather than autotools. As with the other approaches to building SWIG the dependencies need to be installed. The steps below are one of a number of ways of installing the dependencies without requiring Cygwin or MinGW. For fully working build steps always check the Continuous Integration (CI) setups currently detailed in the GitHub Actions YAML file.

  1. Install Nuget from https://www.nuget.org/downloads (v6.0.0 is used in this example, and installed to C:\Tools). Nuget is the package manager for .NET, but allows us to easily install CMake and other dependencies required by SWIG.
  2. Install CMake-win64 Nuget package using the following command:
    C:\Tools\nuget install CMake-win64 -Version 3.15.5 -OutputDirectory C:\Tools\CMake
    Using PowerShell the equivalent syntax is:
    & "C:\Tools\nuget" install CMake-win64 -Version 3.15.5 -OutputDirectory C:\Tools\CMake
    Alternatively you can download CMake from https://cmake.org/download/.
  3. Install the Bison Nuget package using the following command:
    C:\Tools\nuget install Bison -Version 3.7.4 -OutputDirectory C:\Tools\bison
    Alternatively download Bison from https://sourceforge.net/projects/winflexbison/files/ (Bison 3.7.4 is used in this example) and save to a folder e.g. C:\Tools\Bison
  4. Install the PCRE2 Nuget package using the following command:
    C:\Tools\nuget install PCRE2 -Version 10.39 -OutputDirectory C:\Tools\pcre2
    Note this is a x64 build, if this is not suitable PCRE2 can be built from source using https://github.com/PhilipHazel/pcre2/. Alternatively, set WITH_PCRE=OFF to disable PCRE2 support if you are sure you do not require it.
  5. We will also need the SWIG source code. Either download a zipped archive from GitHub, or if git is installed clone the latest codebase using:
    git clone https://github.com/swig/swig.git
    In this example we are assuming the source code is available at C:\swig
  6. Now we have all the required dependencies we can build SWIG using PowerShell and the commands below. We are assuming Visual Studio 2019 is installed. For other versions of Visual Studio change "Visual Studio 16 2019 -A x64" to the relevant Visual Studio Generator and architecture. We add the required build tools to the system PATH, and then build a Release version of SWIG. If all runs successfully a new swig.exe should be generated in the C:/swig/install2/bin folder.

cd C:\swig

$env:PATH="C:\Tools\CMake\CMake-win64.3.15.5\bin;C:\Tools\bison\Bison.3.7.4\bin;" + $env:PATH

cmake -G "Visual Studio 16 2019" -A "x64" `
-DCMAKE_INSTALL_PREFIX="C:/swig/install2" `
-DPCRE2_LIBRARY="$PCRE_ROOT/lib/pcre2-8-static.lib" `
-S . -B build

cmake --build build --config Release
cmake --install build --config Release

# to test the exe built correctly
cd install2/bin
./swig.exe -version
./swig.exe -help

In addition to Release builds you can create a Debug build using:

cmake --build build --config Debug

A Visual Studio solution file should be generated named swig.sln. This can be opened and debugged by running the swig project and setting Properties > Debugging > Command Arguments. For example to debug one of the test-suite .i files included with the SWIG source use the following:

-python -c++ -o C:\Temp\doxygen_parsing.cpp C:\swig\Examples\test-suite\doxygen_parsing.i

3.3.2 Building swig.exe using MSYS2

Download and install MSYS2 from www.msys2.org (tested with version msys2-x86_64-20201109). Launch the MSYS2 shell.

Install the packages needed to build swig:

pacman -S git autoconf automake bison gcc make pcre2-devel

Clone the repository to /usr/src/:

mkdir /usr/src/
cd /usr/src/
git clone https://github.com/swig/swig.git

Configure and build:

cd /usr/src/swig

Finally you may also want to install SWIG:

make install

3.3.3 Building swig.exe using MinGW and MSYS

The short abbreviated instructions follow...

The step by step instructions to download and install MinGW and MSYS, then download and build the latest version of SWIG from Github follow... Note that the instructions for obtaining SWIG from Github are also online at SWIG Bleeding Edge.

Pitfall note: Execute the steps in the order shown and don't use spaces in path names. In fact it is best to use the default installation directories.

  1. Download the following packages from the MinGW download page. Note that at the time of writing, the majority of these are in the Current release list and some are in the Snapshot or Previous release list.
  2. Install MinGW-3.1.0-1.exe (C:\MinGW is default location.)
  3. Install MSYS-1.0.11-2004.04.30-1.exe. Make sure you install it on the same windows drive letter as MinGW (C:\msys\1.0 is default). In the post install script,
  4. Install msysDTK-1.0.1.exe to the same folder that you installed MSYS (C:\msys\1.0 is default).
  5. Copy the following to the MSYS install folder (C:\msys\1.0 is default):
  6. Start the MSYS command prompt and execute:
    cd /
    tar -jxf msys-automake-1.8.2.tar.bz2
    tar -jxf msys-autoconf-2.59.tar.bz2
    tar -zxf bison-2.0-MSYS.tar.gz
  7. The very latest development version of SWIG is available from SWIG on Github and can be downloaded as a zip file or if you have Git installed, via Git. Either download the latest Zip file snapshot and unzip and rename the top level folder to /usr/src/swig. Otherwise if using Git, type in the following:
    mkdir /usr/src
    cd /usr/src
    git clone https://github.com/swig/swig.git
    Pitfall note: If you want to place SWIG in a different folder to the proposed /usr/src/swig, do not use MSYS emulated windows drive letters, because the autotools will fail miserably on those.
  8. The PCRE2 third party library needs to be built next. Download the latest PCRE2 source tarball, such as pcre2-10.39.tar.bz2, from www.pcre.org and place in the /usr/src/swig directory. Build PCRE2 as a static library using the Tools/pcre-build.sh script as follows:
    cd /usr/src/swig
  9. You are now ready to build SWIG. Execute the following commands to build swig.exe:
    cd /usr/src/swig

3.3.4 Building swig.exe using Cygwin

Note that SWIG can also be built using Cygwin. However, SWIG will then require the Cygwin DLL when executing. Follow the Unix instructions in the README file in the SWIG root directory. Note that the Cygwin environment will also allow one to regenerate the autotool generated files which are supplied with the release distribution. These files are generated using the autogen.sh script and will only need regenerating in circumstances such as changing the build system. Running the examples on Windows using Cygwin

The examples and test-suite work as successfully on Cygwin as on any other Unix operating system. The modules which are known to work are Python, Tcl, Perl, Ruby, Java and C#. Follow the Unix instructions in the README file in the SWIG root directory to build the examples.

3.4 Microsoft extensions and other Windows quirks

A common problem when using SWIG on Windows are the Microsoft function calling conventions which are not in the C++ standard. SWIG parses ISO C/C++ so cannot deal with proprietary conventions such as __declspec(dllimport), __stdcall etc. There is a Windows interface file, windows.i, to deal with these calling conventions though. The file also contains typemaps for handling commonly used Windows specific types such as __int64, BOOL, DWORD etc. Include it like you would any other interface file, for example:

%include <windows.i>

__declspec(dllexport) ULONG __stdcall foo(DWORD, __int32);

Note that if you follow Microsoft's recommendation of wrapping the __declspec calls in a preprocessor definition, you will need to make sure that the definition is included by SWIG as well, by either defining it manually or via a header. For example, if you have specified the preprocessor definition in a header named export_lib.h and include other headers which depend on it, you should use the %include directive to include the definition explicitly. For example, if you had a header file, bar.h, which depended on export_lib.h, your SWIG definition file might look like:

// bar.i
%module bar
%include <windows.i>
%include "export_lib.h"
%include "bar.h"

where export_lib.h may contain:

// export_lib.h
#define BAR_API __declspec(dllexport)

and bar.h may look like:

// bar.h
#include "export_lib.h"
BAR_API void bar_function(int, double);

Using the preprocessor to remove BAR_API is a popular simpler solution:

// bar.i
%module bar
#define BAR_API
%include "bar.h"