Problems trying to cross-compile JUCE v7 on Linux to Windows target

Development
1

Hi everyone,

I have some issues cross-compiling a standalone JUCE v7.0.0 application to Windows from a Ubuntu docker container. If you have some ideas what I could try I’d be grateful for your help.

I tried the mingw-64 (x86-64-w64-mingw32-posix) as well as the llvm-mingw toolchain (x86_64-w64-mingw32-clang++) and I’m getting pretty much the same errors :

There seems to be a problem with the declaration of the _clearfp function in JUCE/modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp on line 71. Im getting the following error:

[ 56%] Building CXX object CMakeFiles/LaboratoriumAudioServer.dir/JUCE/modules/juce_audio_processors/juce_audio_processors.cpp.obj
In file included from /build/JUCE/modules/juce_audio_processors/juce_audio_processors.cpp:205:
/build/JUCE/modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp:71:18: error: functions that differ only in their return type cannot be overloaded
 extern "C" void _clearfp();
            ~~~~ ^
/llvm-mingw/x86_64-w64-mingw32/include/float.h:266:46: note: previous declaration is here
_CRTIMP unsigned int __cdecl __MINGW_NOTHROW _clearfp (void);   /* Clear the FPU status word */
        ~~~~~~~~~~~~                         ^

If I change the relevant line

 extern "C" void _clearfp();

to

 extern "C" unsigned int _clearfp();

I’m not getting that error anymore, but then there are some problems with included headers in JUCE/modules/juce_gui_basics/juce_gui_basics.cpp on line 65, namely the headers UIAutomation.h and Dxgi.h can not be found.

If I remove those includes, I’m getting numerous other errors, probably because symbols from those headers can not be found.

Is there a way to make the cross-compilation work, maybe with a different JUCE version?

Thanks very much for your help.

2

There were some improvements in this area recently. Please try the latest version of JUCE from the develop branch.

That said, cross-compiling is not officially supported, and we don’t test it at all, so it’s still not guaranteed to work.

3

Thanks very much for the tip reuk, that gets me somewhere! :slight_smile:

The app compiles using x86_64-w64-mingw32-g++-posix with JUCE on the develop branch (on commit 7b61bdfba).

I still had to use

extern "C" unsigned int _clearfp();

though, and explicitly disable JUCE_PLUGINHOST_LV2 (but I guess that makes sense for a Windows build).

The linker still fails however, and at this point I don’t exactly know why, but I’ll report back when I figure something out.

As for llvm-mingw / clang: That also compiles with the fixes above, but the linker cannot find the libatomic1 library.

4

I had a dig through my shell history, and it looks like the last time I tested this out, I was using the following CMake flags, where the llvm-mingw-20220323-ucrt-ubuntu-18.04-x86_64 folder is one of the pre-built releases from the project page.

"CMAKE_SYSTEM_NAME": "Windows",
"CMAKE_C_COMPILER": "$env{HOME}/development/llvm-mingw-20220323-ucrt-ubuntu-18.04-x86_64/bin/x86_64-w64-mingw32-clang",
"CMAKE_CXX_COMPILER": "$env{HOME}/development/llvm-mingw-20220323-ucrt-ubuntu-18.04-x86_64/bin/x86_64-w64-mingw32-clang++",
"CMAKE_CXX_FLAGS": "-static",
"CMAKE_BUILD_TYPE": "Debug",
"CMAKE_FIND_ROOT_PATH": "$env{HOME}/development/llvm-mingw-20220323-ucrt-ubuntu-18.04-x86_64/x86-64-w64-mingw32"

These flags allow me to successfully build the AudioPluginHost, including LV2 hosting functionality, and without making any changes to JUCE. Getting VST2 hosting to work does require changing/removing the _clearfp and _fpreset declarations, as you discovered.

Alternatively, Fedora provides a mingw64-filesystem package that includes mingw64-cmake, a wrapper around CMake that automatically sets up the build environment for cross-compiling. By default, this will use GCC rather than Clang. The following command produced a working build tree:

mingw64-cmake -B cmake-mingw64 -D JUCE_BUILD_EXTRAS=ON -D JUCE_BUILD_EXAMPLES=ON -D CMAKE_BUILD_TYPE=Debug -D JUCE_GLOBAL_VST2_SDK_PATH=~/development/VSTSDK -D CMAKE_CXX_FLAGS=-static
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