mingw cross compilation from Linux to Windows

[NeroBurner]

as mentioned over at hunter ruslo/hunter#846

I don't know where to put this file so I created this issue

contents of Toolchain-Ubuntu-mingw64.cmake

# Sample toolchain file for building for Windows from an Ubuntu Linux system.
#
# Typical usage:
#    *) install cross compiler: `sudo apt-get install mingw-w64 g++-mingw-w64`
#    *) cd build
#    *) cmake -DCMAKE_TOOLCHAIN_FILE=~/Toolchain-Ubuntu-mingw64.cmake ..

set(CMAKE_SYSTEM_NAME Windows)
set(TOOLCHAIN_PREFIX x86_64-w64-mingw32)

# cross compilers to use for C and C++
set(CMAKE_C_COMPILER ${TOOLCHAIN_PREFIX}-gcc)
set(CMAKE_CXX_COMPILER ${TOOLCHAIN_PREFIX}-g++)
set(CMAKE_Fortran_COMPILER ${TOOLCHAIN_PREFIX}-gfortran)
set(CMAKE_RC_COMPILER ${TOOLCHAIN_PREFIX}-windres)

# target environment on the build host system
#   set 1st to dir with the cross compiler's C/C++ headers/libs
set(CMAKE_FIND_ROOT_PATH /usr/${TOOLCHAIN_PREFIX})

# modify default behavior of FIND_XXX() commands to
# search for headers/libs in the target environment and
# search for programs in the build host environment
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

[ruslo]

Looks similar to:

• https://github.com/ruslo/polly/blob/master/compiler/gcc-cross-compile.cmake

I guess you can start with:

• https://github.com/ruslo/polly/blob/master/linux-gcc-x64.cmake

To create linux-mingw64 toolchain.

[ruslo]

set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

I think we don't need this if you're using Hunter. find_package should never return anything from system if Hunter used, see:

• https://docs.hunter.sh/en/latest/faq/interaction-with-other-package-managers.html

[NeroBurner]

where should I set the windres variable needed for cross-compiling to windows

set(CMAKE_RC_COMPILER ${TOOLCHAIN_PREFIX}-windres)

Edit:
and more importantly, where is the following variable set?

set(CMAKE_SYSTEM_NAME Windows)

[ruslo]

set(CMAKE_RC_COMPILER ${TOOLCHAIN_PREFIX}-windres)

I think it will not hurt if we will add it to the compiler/gcc-cross-compile.cmake.

set(CMAKE_SYSTEM_NAME Windows)

In top linux-mingw64.

[NeroBurner]

should we add emulator support?
https://cmake.org/cmake/help/v3.3/variable/CMAKE_CROSSCOMPILING_EMULATOR.html

with this we could run mingw-w64 cross compiled tests with wine64 or armhf targets with qemu

[ruslo]

should we add emulator support?

It will not hurt I guess. Is emulator a part of mingw-w64 package?

[NeroBurner]

no, it would need an extra emulator installed. And for mingw that would be wine (to run windows binaries)

[ruslo]

no, it would need an extra emulator installed

In this case we can add CMAKE_CROSSCOMPILING_EMULATOR variable but only if it will not return error if emulator not found.

[ruslo]

Closing inactive discussion.