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openfoam/doc/cross-compile-mingw.md
Mark Olesen 6630fb2b69 STYLE: adjust wording in compilation notes
2019-05-08 16:51:14 +02:00

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Notes for cross-compiling with mingw

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 tools used during compilation. These are found under wmake/src. When these are compiled they will create executables that work on the target platform (Windows), but not on the host platform.

The workaround:

  1. Activate the native OpenFOAM environment (Linux with system gcc) and use that to compile the build tools
wmake/src/Allmake

This can be skipped if you already have an existing OpenFOAM build.

  1. Activate the OpenFOAM for cross-compiling (Linux with mingw) and use that to compile the build tools
wmake/src/Allmake
  1. Copy the contents of the native platform build tools into the cross-compilation platform directory. For example,
cp wmake/platforms/linux64Gcc/* wmake/platforms/linux64Mingw/

The wmake/platforms/linux64Mingw/ directory should now contain native and cross-compiled tools:

dirToString     dirToString.exe
wmkdep          wmkdep.exe
wmkdepend       wmkdepend.exe

The native tools are the one that will (automatically) be used throughout the balance of the cross-compilation process.

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 (2019-05-01)

  • 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.