= How to use MinGW to cross compile software for Windows =
MinGW is the GNU toolchain for Windows, it also exists as cross compiler under
Linux (and probably other UNIXes). You can use it to build Windows software on Linux.
== Install the mingw cross compiling toolchain ==
There are several ways to get the mingw cross compiler on your machine.
With Ubuntu/Debian you can simply install it using apt: "apt-get install mingw32". This will
install the toolchain as i586-mingw32msvc-gcc to /usr/bin/ .
You can of course also build this toolchain from sources yourself, but this is more work.
== Write a CMake toolchain file ==
For CMake to be able to crosscompile software, it requires you to write a toolchain file, which tells CMake
some information about the toolchain.
With the examples used above it will look like:
# the name of the target operating system
# which compilers to use for C and C++
# here is the target environment located
SET(CMAKE_FIND_ROOT_PATH / usr/ i586-mingw32msvc /home/alex/mingw-install )
# adjust the default behaviour of the FIND_XXX() commands:
# search headers and libraries in the target environment, search
# programs in the host environment
Save this file as Toolchain-mingw32.cmake to some location where you will put
all your toolchain files, e.g. $HOME.
As you can see CMAKE_FIND_ROOT_PATH is set to /usr/i586-mingw32msvc, which contains the headers and libraries
installed with the toolchain, and /home/ alex/mingw-install/. This second directory is intended to hold
other libraries you will compile using mingw32, they should be installed under this install prefix. This way
the FIND_XXX() commands in CMake will find both the headers and libraries coming with the toolchain as well
as additional libraries you have built for this platform.
You can try this toolchain file as well [[File:Toolchain-cross-mingw32-linux.cmake ]] which is trying to be
as simple as possible by only setting COMPILER_PREFIX var.
== Build the software for Windows ==
Let's say you have the classical hello world software with a CMake based buildsystem and want to build this for Windows
Then run CMake on it to generate the buildfiles, the important point is that you tell it to use the toolchain file you just wrote:
~/src/helloworld/ $ mkdir build
~/src/helloworld/ $ cd build
~/src/ helloworld/ build/ $ cmake -DCMAKE_TOOLCHAIN_FILE=~/ Toolchain-mingw32.cmake -DCMAKE_INSTALL_PREFIX=/ home/ alex/mingw-install ..
-- Configuring done
-- Generating done
-- Build files have been written to: /home/alex/src/helloworld/build
~/src/helloworld/build/ $ make
Scanning dependencies of target hello
[100%] Building C object CMakeFiles/hello. dir/main.o
Linking C executable hello.exe
[100%] Built target hello
So that's all. It actually doesn't matter whether it's just a "hello world" or some complex piece of software,
the only difference is the usage of the toolchain file. If the software has all required configure checks, it should just
build also with this toolchain.