Current LLD 20 fails to link dependency in liblldMachO.a correctly

[lerno]

linking liblldMachO.a fails on a vanilla Linux build, with the following code:

/usr/bin/ld: /usr/lib/llvm-20/lib/liblldMachO.a(BPSectionOrderer.cpp.o): in function `lld::macho::runBalancedPartitioning(llvm::StringRef, bool, bool, bool, bool)':
(.text._ZN3lld5macho23runBalancedPartitioningEN4llvm9StringRefEbbbb+0x2fc): undefined reference to `lld::BPSectionBase::reorderSectionsByBalancedPartitioning(llvm::StringRef, bool, bool, bool, bool, llvm::SmallVector<std::unique_ptr<lld::BPSectionBase, std::default_delete<lld::BPSectionBase> >, 6u>&)'

This first started happening around Dec 19 2024, so is related some change during that time.

[lerno]

The missing function seems to be reorderSectionsByBalancedPartitioning

[carlocab]

Sounds like #117514.

[Colibrow]

Let me take a look.

[Colibrow]

@lerno Can you provide the build environment and commands for me to reproduce this? I tested on my ubuntu-22.04 with build-in ld and c/c++ but not reproduced.
Commands are below

mkdir build
cd build
cmake -G Ninja \
      -DLLVM_ENABLE_PROJECTS=lld \
      -DCMAKE_BUILD_TYPE=Release \
      ../llvm
ninja lld

[lerno]

This is the build script: https://github.com/c3lang/c3c/blob/master/CMakeLists.txt

Here is the CI entry to build it so you can see how it's invoked:

https://github.com/c3lang/c3c/blob/4cb984e56d658c269764c56418d93c237e7fd4df/.github/workflows/main.yml#L225

This is the build arguments for that makefile:

cmake -B build \
                -G Ninja \
                -DCMAKE_BUILD_TYPE=${{matrix.build_type}} \
                -DCMAKE_C_COMPILER=clang-${{matrix.llvm_version}} \
                -DCMAKE_CXX_COMPILER=clang++-${{matrix.llvm_version}} \
                -DCMAKE_LINKER=lld-link-${{matrix.llvm_version}} \
                -DCMAKE_OBJCOPY=llvm-objcopy-${{matrix.llvm_version}} \
                -DCMAKE_STRIP=llvm-strip-${{matrix.llvm_version}} \
                -DCMAKE_DLLTOOL=llvm-dlltool-${{matrix.llvm_version}} \
                -DC3_LLVM_VERSION=${{matrix.llvm_version}}
          cmake --build build

[Colibrow]

@lerno The order of the link needs to be reversed.
https://github.com/c3lang/c3c/blob/5ba9acad5d46903c1539d5290c67a8c7e55dd5d2/CMakeLists.txt#L255-L260
e.g.

 ${LLD_WASM} 
 ${LLD_MINGW} 
 ${LLD_ELF} 
 ${LLD_MACHO} 
 ${LLD_COMMON} 

liblldMachO.a references reorderSectionsByBalancedPartitioning in liblldCommon.a.
When processing archive symbols, libraries that provide symbols must come after the libraries that use them.
For further information on symbol processing, you can visit https://maskray.me/blog/2021-06-20-symbol-processing.

[lerno]

Ah! I didn't even think about looking at that because I had gotten used to LLVM sometimes breaking. So I was incorrectly assuming I failed to link something that was now expected but may not in the LLD CMake scripts or something. So simple...

[lerno]

Might be worth adding a note to the releasenotes to make people aware of this stricter link ordering though.

[lerno]

I can verify that this fixed the build. Should I close this issue?

[Colibrow]

I can verify that this fixed the build. Should I close this issue?

Since the build has been fixed, I think the issue can be closed.