Mix GCC-based MinGW-w64 with llvm-mingw

[faded-showplace715]

This is the setup I want to do on my local computer.

It has been unable to build LLVM with GCC for a while: brechtsanders/winlibs_mingw#259.

The winlibs.com distro no longer include LLVM.

I want something like MSYS2's https://packages.msys2.org/packages/mingw-w64-ucrt-x86_64-clang, that will use GCC libraries and tools instead of pure LLVM like llvm-mingw. But I don't want to build my own LLVM.

Is it possible for me to configure llvm-mingw to do so?

[mstorsjo]

For your use case, I think the easiest thing to do is to download a release of llvm-mingw, extract bin/clang-21.exe, bin/libclang-cpp.dll, bin/libLLVM-21.dll, bin/libc++.dll and bin/libunwind.dll and put them into the bin directory of your GCC toolchain. You'll also need to copy over lib/clang into the lib directory of the GCC toolchain. While doing that, you may want to rename clang-21.exe into plain clang.exe. (This, because in llvm-mingw, clang.exe is a small wrapper, so the real clang binary is renamed.) You may wish to copy clang.exe to a separate clang++.exe as well. (On Unix it's symlinked - it's the same executable, it just looks at what name it was executed as.) If you want LLD as well, you can copy bin/ld.lld.exe.

This way you should have a totally "vanilla" Clang available for use. The customization to make it use compiler-rt and libunwind instead of libgcc, LLD instead of GNU ld, libc++ instead of libstdc++, isn't baked into the Clang executable, but is set through Clang config files (bin/*.cfg). Without them in the same directory, Clang reverts to its normal defaults (looking for a suitable GCC install, using libstdc++ from there etc) instead. The fact that the Clang binary itself is linked against a different C++ standard library doesn't have any effect on what code it generates or links against.