openfoam/doc/Cross-Compile-mingw.md

Notes for cross-compiling with mingw

Minimum version

The mingw cross-compiler should be at least version 8.2.0 (tested) or slightly older. Versions that are much older may have faulty regex implementations.

Host setup

On openSUSE use the packages for compilation:

mingw64-cross-binutils
mingw64-cross-cpp
mingw64-cross-gcc
mingw64-cross-gcc-c++
mingw64-filesystem
mingw64-headers
mingw64-runtime

mingw64-libwinpthread1
mingw64-winpthreads-devel

mingw64-libfftw3
mingw64-fftw3-devel

This setup is missing zlib, so download that manually and compile as a static library.

CC="$(wmake -show-c)" CFLAGS="$(wmake -show-cflags)" ./configure --static
make

The resulting output files (zconf.h, zlib.h) and (libz.a) either need to be installed in system locations where OpenFOAM can find them, or if they are to be shipped directly with OpenFOAM, they can also be placed in the src/OpenFOAM/include and platforms/XXX/lib paths.

If the header files are only needed during compilation, it can be a fairly convenient hack to simply place copies of them in the src/OSspecific/MSwindows directory.

Flex is used in a few locations within OpenFOAM for generating code. The generated C++ code requires the FlexLexer.h header file, but its /usr/include location will be ignored by the cross-compiler.

As another ugly hack, a copy of this file can be made in a standard project include location. For example,

ln -s /usr/include/FlexLexer.h src/OSspecific/MSwindows

The last point to consider when cross-compiling is the behaviour of the OpenFOAM wmake toolchain used during compilation. These are found under wmake/src. If the Makefile is used directly, executables will be created that work on the target platform (Windows), but not on the host platform (which is what is required). This is addressed directly by the wmake/src/Allmake script, which will use the system gcc to create host binaries for the wmake toolchain. If, for some reason, you also require target wmake toolchain binaries, you will need invoke make manually within the wmake/src directory.

The settings for cross-compilation are normally defined in the etc/pref.sh file with contents like this:

# For mingw cross-compile

export WM_COMPILER=Mingw
export WM_MPLIB=MSMPI

export WM_LABEL_SIZE=32
# other settings...

Additional adjustments may be required in some other places. For example in etc/config.sh/FFTW

fftw_version=fftw-system
export FFTW_ARCH_PATH=/usr/x86_64-w64-mingw32/sys-root/mingw

Run-time setup

When using the cross-compiled executables and libraries, the corresponding runtime libraries will be required. These will need to be copied across from the Linux host system to the target machine. On openSUSE these runtime libraries are provided by the packages:

mingw64-libgcc_s_seh1
mingw64-libstdc++6

When running, the WM_PROJECT_DIR environment must be set. OpenFOAM will otherwise not be able to locate its files.

Known limitations (2019-06-24)

• kahip does not build
• boost should build ok, but no CGAL support (ie, no foamyHexMesh)
• no ParaView plugin, runTimePostProcessing
• reacting EulerFoam solvers have too many interdependencies and do not yet compile cleanly. It is advisable to compile with the wmake -k option to keep going even when the EulerFoam solvers fail to compile.