MinGW: Remove manual setting of library prefix/suffix

[qmfrederik]

We no longer need to manually set these suffixes/prefixes as CMake in MSYS2 now knows about Objective C.

See msys2/MINGW-packages#20028
See https://gitlab.kitware.com/cmake/cmake/-/merge_requests/9244
See msys2/MINGW-packages#20024 (comment)

/cc @MehdiChinoune

[MehdiChinoune]

I don't where does the issue come from, those are set by default by CMake, they shouldn't be added at all.

[qmfrederik]

My best guess is that this is because the CMake project declares itself as a OBJC/OBJCXX project, and CMake may not have sensible defaults for Objective-C on MSYS2/MINGW and friends.

[MehdiChinoune]

My best guess is that this is because the CMake project declares itself as a OBJC/OBJCXX project, and CMake may not have sensible defaults for Objective-C on MSYS2/MINGW and friends.

We should add support for MinGW for OBJC/OBJCXX to CMake.
I will try to patch CMake and upstream.

[MehdiChinoune]

@qmfrederik Do you know which clang library has objc_alloc, objc_alloc_init and objc_allocWithZone symbols?

[davidchisnall]

Do you know which clang library has objc_alloc, objc_alloc_init and objc_allocWithZone symbols?

These are not provided by clang, they are provided by libobjc2.

[MehdiChinoune]

Do you know which clang library has objc_alloc, objc_alloc_init and objc_allocWithZone symbols?

These are not provided by clang, they are provided by libobjc2.

I am trying to support OBJ/OBJCXX on CMake, but It fails with undefined reference to those symbols!
Looks like they weren't exported.

[qmfrederik]

@MehdiChinoune Have you got a small repo? libobjc2 does export those symbols. You also need to make sure you use the right clang parameters -- e.g. -fobjc-runtime=gnustep-2.0 if you you use the libobjc2.0 runtime.

[MehdiChinoune]

@MehdiChinoune Have you got a small repo? libobjc2 does export those symbols. You also need to make sure you use the right clang parameters -- e.g. -fobjc-runtime=gnustep-2.0 if you you use the libobjc2.0 runtime.

It's about this repo, I am testing your PR in MinGW-package

[davidchisnall]

Those symbols won’t be exported from anywhere until libobjc2 is built…

[MehdiChinoune]

Those symbols won’t be exported from anywhere until libobjc2 is built…

The issue appears when building tests, but that occurs with LLVM/Clang 18.1.0-rc2.
It builds successfully with 17.0.6

[qmfrederik]

@MehdiChinoune Thanks for your patches for cmake (msys2/MINGW-packages#20028). I've removed the the hard-coded values for CMAKE_IMPORT_LIBRARY_SUFFIX, CMAKE_LINK_LIBRARY_SUFFIX, and CMAKE_SHARED_LIBRARY_PREFIX and the the shared library and linker library now get installed as bin/libobjc.dll and lib/libobjc.dll.a.

Can you confirm this is what you had in mind?

[MehdiChinoune]

Yes, fixing shared/import libraries suffix/prefix was the intention.
before you merge this PR, could you try setting LINKER_LANGUAGE (https://cmake.org/cmake/help/latest/prop_tgt/LINKER_LANGUAGE.html) to CXX and see if it fixes the required LDFLAGS.

[qmfrederik]

@MehdiChinoune I tried:

• Setting _DLINKER_LANGUAGE=CXX but that variable is not used: "CMake Warning: Manually-specified variables were not used by the project: LINKER_LANGUAGE"
• I thought I could perhaps pull in stdc++ and gcc_s into ObjC projects by setting CMAKE_OBJC_IMPLICIT_LINK_LIBRARIES to CMAKE_CXX_IMPLICIT_LINK_LIBRARIES. That causes the code to link with a bunch of other libraries, too (including mingwex and mingw32) which causes the exception handling tests to fail

Long story short, I would leave it at this for now -- we can always revisit later and try to optimize things.

[qmfrederik]

@davidchisnall I think this is ready now -- long story short: there was a workaround to manually set the library prefix/suffix, but this is no longer needed as CMake in MSYS2 now knows about ObjC. Do you agree?

[davidchisnall]

With the caveat that I don't have a Windows machine to try this on, it looks fine.

[davidchisnall]

Build looks green for MinGW CI, and I'm in favour of removing complexity from the build system if it is not essential.

[MehdiChinoune]

@MehdiChinoune I tried:

• Setting _DLINKER_LANGUAGE=CXX but that variable is not used: "CMake Warning: Manually-specified variables were not used by the project: LINKER_LANGUAGE"

LINKER_LANGUAGE is a target property, It couldn't be passed by command.

[qmfrederik]

@MehdiChinoune Do you know which clang library has objc_alloc, objc_alloc_init and objc_allocWithZone symbols?

You were right, they weren't being exported on Windows. I've included a fix for that in #280.