CrossQuickstart

A more recent guide for building a cross-compiler in a Linux environment exists here

Cross Compilation Quickstart

The Need for Cross Compilers

In a nutshell, cross compilers enable you to build applications that run on a different type of platform than the platform you're developing on. For example, you may wish to develop libraries on a Linux-based system for use on a Windows-based system. Or you may wish to develop an application on a Windows-based system for use on an ARM-based embedded system. In both cases, it's the cross compiler that allows you to develop and build native applications for the other platform.

The platform on which you're developing and compiling is called the build platform while the platform on which your libraries and applications run is called the host platform.

If you never build for a different host platform, there's no real need for a cross compiler. A native compiler that builds for the same host platform that you're developing on is really all you need to create the next killer app.

Cross Compiling with GNU Autotools

Compilers based upon the GNU Compiler Collection (GCC), such as the ones from the MinGW-w64 project, can be built as cross compilers or native compilers. A developer building for a different platform simply installs (or builds) a cross compiling GCC toolchain and any required headers and libraries. The developer then runs a configure script with the appropriate --build and --host arguments that enable the configure script to determine which cross compiler to use. The configure script creates a customized Makefile to build the binaries that run natively on the specified host platform. Finally, the developer runs make to perform the build.

The values used for the --build and --host arguments are described in more detail on the System Type Triplets page.

While the GNU Build System and the configure script remove much of the complexity of cross compiling, you will find source packages in the wild that don't use a build system but still enable enable cross compilation. For example, many source packages that have no need for the complexity of a setting up and maintaining a build system provide a custom Makefile used by both native and cross compilers. Cross compilation support is typically provided by the Makefile with lines such as

CC := $(CROSS_COMPILE)gcc
WINDRES := $(CROSS_COMPILE)windres
AR := $(CROSS_COMPILE)ar
STRIP := $(CROSS_COMPILE)strip

You may also discover Makefile's that require you to explicitly set environment variables as part of the make invocation to allow cross compilation, similar to

make -f lazy_makefile CC=i686-w64-mingw32-gcc

Other popular build systems such as Cmake and Waf also support cross compilation.

Cross Compilation and the MinGW-w64 Project

The MinGW-w64 project supports toolchains targeting 32 and 64-bit systems running the Windows operating system. As the project supports building native Windows binaries from Unix-like platforms, cross compilation is a very important part of the MinGW-w64 project.

TODO more content about the MinGW-w64 native and cross compilers

TODO briefly discuss the two main perspectives; MinGW-w64 hacker and MinGW-w64 user a la @Mook

TODO add content on personal builds

MinGW-w64 Supported Platforms

When cross compiling, MinGW-w64 toolchains support two platforms identified with the following two type triplets. For more information on type triplets see the System Type Triplets page.

1. i686-w64-mingw32 for binaries built to run on 32-bit Windows platforms.
2. x86_64-w64-mingw32 for binaries built to run on 64-bit Windows platforms.

Cross Compilation Examples

The following examples should run fine on any Unix-like system with a sane build system, but to run the examples on a Windows system you'll need a collection of Unix tools such as bash, sed, gawk, grep, make, and others. The MSYS collection from the MSYS SourceForge files site or the MinGW-w64 hosted MSYS is a convenient way to get the required tools. Once the tools are installed, make sure they are available in you PATH environment variable.

# [Win7] configure Ruby trunk with 32bit cross compiler
C:\ruby\build>sh -c "../configure --host=i686-w64-mingw32 --enable-shared --disable-install-doc"

TODO add Linux example and GCC cross compiler example