[LLD] Undefined references with linking with -lunwind-ptrace and -unwind-generic

[Kmeakin]

lld reports undefined references, while ld is able to link this without issue:

main.c:

int main() {}

clang main.c -lunwind-ptrace -lunwind-generic produces no error.

clang main.c -lunwind-ptrace -lundwind-genric -fuse-ld=lld produces:

ld.lld: error: /lib/x86_64-linux-gnu/libunwind-ptrace.so: undefined reference to lzma_stream_buffer_decode [--no-allow-shlib-undefined]
ld.lld: error: /lib/x86_64-linux-gnu/libunwind-ptrace.so: undefined reference to lzma_index_uncompressed_size [--no-allow-shlib-undefined]
ld.lld: error: /lib/x86_64-linux-gnu/libunwind-ptrace.so: undefined reference to lzma_index_end [--no-allow-shlib-undefined]
ld.lld: error: /lib/x86_64-linux-gnu/libunwind-ptrace.so: undefined reference to lzma_index_buffer_decode [--no-allow-shlib-undefined]
ld.lld: error: /lib/x86_64-linux-gnu/libunwind-ptrace.so: undefined reference to lzma_stream_footer_decode [--no-allow-shlib-undefined]
ld.lld: error: /lib/x86_64-linux-gnu/libunwind-ptrace.so: undefined reference to lzma_index_size [--no-allow-shlib-undefined]
clang: error: linker command failed with exit code 1 (use -v to see invocation)

clang --version:

Ubuntu clang version 15.0.0-++20220321012320+9aa52ba574ad-1~exp1~20220321012418.363
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

ld.lld --version:

Ubuntu LLD 15.0.0 (compatible with GNU linkers)

[llvmbot]

@llvm/issue-subscribers-lld-elf

[MaskRay]

Not a bug. See https://maskray.me/blog/2021-06-13-dependency-related-linker-options#no-allow-shlib-undefined

Your main executable needs to link in liblzma for lzma_stream_buffer_decode and other symbols.

[Kmeakin]

I believe this should be considered a bug. lld is described as "a drop in replacement for bfd and gold". This implies that it should be possible to append -fuse-ld=lld to a compiler invocation and get the same behavior.