Cross compilation of FMUs under Windows

[Rüdiger Franke]

Recently a 64bit Windows version of OpenModelica was introduced. A separate 32bit version is still needed for the export of 32bit FMUs. This should be covered with cross compilation instead.

Cross compilation already works under Linux, including an extended

CevalScriptBackend.buildModelFMU(className = "MyModel", platforms = {"i686-w64-mingw32"})

where platforms is a list of "static", "dynamic" and target triplets, like 32 bit windows in the example. Moreover the OMEdit configuration of FMI export was extended for cross compilation (Tools -> Options -> FMI). The C runtime implements cross compilation of minimal FMUs including source code; the Cpp runtime implements export of full FMUs using pre-compiled runtime libs for the respective target platform.

The Windows version of OpenModelica should at least support cross compilation of 32bit Windows FMUs from the 64bit Windows version. This would make a separate 32bit Windows version of OpenModelica obsolete.

If cross compilation shall work like under Linux then we need:

• compilers with the name i686-w64-mingw32-gcc and i686-w64-mingw32-g++ (OMEdit and the FMU makefiles would expect it)
• static versions of libgcc and libstdc++ (and possibly libwinpthread) along with these compilers
• call the Cpp FMU makefile with a triplet argument TARGET_TRIPLET=i686-w64-mingw32 (this happens automatically if checked in OMEdit, calling CevalScriptBackend.buildModelFMU with platforms argument)
• an additional version of the Cpp runtime *_static libs generated with this compiler and placed in the directory "$(OMHOME)/lib/$(TARGET_TRIPLET)/omc/cpp"

The concept of the target triplet might be extended to msvc. Then msvc libs would not be placed in subdirectories of the gcc libs anymore, like

$(OMHOME)/lib/omc/cpp/msvc

but besides the gcc libs using another TARGET_TRIPLET, like

$(OMHOME)/lib/$(TARGET_TRIPLET_FOR_MSVC)/omc/cpp