llvm@16's version of llvm-config doesn't include the correct -L flag for zstd when passed --link-static on Apple-silicon-based Macs

[jordydickinson]

brew gist-logs <formula> link OR brew config AND brew doctor output

% brew gist-logs llvm@16
Error: No logs.
% brew config
HOMEBREW_VERSION: 4.2.0
ORIGIN: https://github.com/Homebrew/brew
HEAD: ff899e5b3ff6731208564ef502db237e2627e8ba
Last commit: 11 days ago
Core tap JSON: 25 Dec 19:29 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_MAKE_JOBS: 8
Homebrew Ruby: 3.1.4 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.1.4/bin/ruby
CPU: octa-core 64-bit dunno
Clang: 15.0.0 build 1500
Git: 2.39.3 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 8.4.0 => /usr/bin/curl
macOS: 14.2.1-arm64
CLT: 15.1.0.0.1.1700200546
Xcode: 15.1
Rosetta 2: false
% brew doctor
Your system is ready to brew.

Verification

• My "brew doctor output" says Your system is ready to brew. and am still able to reproduce my issue.
• I ran brew update and am still able to reproduce my issue.
• I have resolved all warnings from brew doctor and that did not fix my problem.
• I searched for recent similar issues at https://github.com/Homebrew/homebrew-core/issues?q=is%3Aissue and found no duplicates.

What were you trying to do (and why)?

I was trying to use the OCaml LLVM bindings (package llvm) available via OPAM. This depends on conf-llvm which in turn depends on the Homebrew installation of llvm@16.

What happened (include all command output)?

The OPAM package fails to install (see here) due to not being able to find zstd. Moreover, /opt/homebrew/Cellar/llvm@16/16.0.6/bin/llvm-config --cflags --system-libs --ldflags --link-static --libs Core fails to provide the correct linker flags for zstd. (In particular, it is missing the flag -L/opt/homebrew/opt/zstd/lib.)

What did you expect to happen?

I expected the output of /opt/homebrew/Cellar/llvm@16/16.0.6/bin/llvm-config --cflags --system-libs --ldflags --link-static --libs Core to include the flag -L/opt/homebrew/opt/zstd/lib.

Step-by-step reproduction instructions (by running brew commands)

% brew install llvm@16
==> Downloading https://ghcr.io/v2/homebrew/core/llvm/16/manifests/16.0.6-1
Already downloaded: /Users/jordydickinson/Library/Caches/Homebrew/downloads/6d953f5e2900ae03526365fe19bb6b07931a3ff7d59b0432827a91fb42348015--llvm@16-16.0.6-1.bottle_manifest.json
==> Fetching llvm@16
==> Downloading https://ghcr.io/v2/homebrew/core/llvm/16/blobs/sha256:9bab38bfbe
Already downloaded: /Users/jordydickinson/Library/Caches/Homebrew/downloads/08c2413cfd17a6c2d04c8fe386b5c301f4dfb24d275ae55a936ff68ca2491b2a--llvm@16--16.0.6.arm64_sonoma.bottle.1.tar.gz
==> Pouring llvm@16--16.0.6.arm64_sonoma.bottle.1.tar.gz
==> Caveats
To use the bundled libc++ please add the following LDFLAGS:
  LDFLAGS="-L/opt/homebrew/opt/llvm@16/lib/c++ -Wl,-rpath,/opt/homebrew/opt/llvm@16/lib/c++"

llvm@16 is keg-only, which means it was not symlinked into /opt/homebrew,
because this is an alternate version of another formula.

If you need to have llvm@16 first in your PATH, run:
  echo 'export PATH="/opt/homebrew/opt/llvm@16/bin:$PATH"' >> ~/.zshrc

For compilers to find llvm@16 you may need to set:
  export LDFLAGS="-L/opt/homebrew/opt/llvm@16/lib"
  export CPPFLAGS="-I/opt/homebrew/opt/llvm@16/include"
==> Summary
🍺  /opt/homebrew/Cellar/llvm@16/16.0.6: 6,767 files, 1.5GB
==> Running `brew cleanup llvm@16`...
Disable this behaviour by setting HOMEBREW_NO_INSTALL_CLEANUP.
Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
% /opt/homebrew/Cellar/llvm@16/16.0.6/bin/llvm-config --cflags --system-libs --ldflags --link-static --libs Core
-I/opt/homebrew/Cellar/llvm@16/16.0.6/include  -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
-L/opt/homebrew/Cellar/llvm@16/16.0.6/lib -Wl,-search_paths_first -Wl,-headerpad_max_install_names
-lLLVMCore -lLLVMRemarks -lLLVMBitstreamReader -lLLVMBinaryFormat -lLLVMTargetParser -lLLVMSupport -lLLVMDemangle
-lm /opt/homebrew/lib/libz3.dylib -lz -lzstd -lcurses -lxml2

[Bo98]

This is likely an upstream llvm-config issue unfortunately.

With z3 it just takes the full path: https://github.com/llvm/llvm-project/blob/64f0681e97c6046912dc0d80bc56709f72045338/llvm/lib/Support/CMakeLists.txt#L91

However with zstd it strips that down to the basename but never adds a -L to compensate anywhere: https://github.com/llvm/llvm-project/blob/64f0681e97c6046912dc0d80bc56709f72045338/llvm/lib/Support/CMakeLists.txt#L312-L323

--system-libs is just a simple wrapper that outputs that LLVMSupport LLVM_SYSTEM_LIBS property.

The comments in that file suggest the long-term ambition is to deprecate llvm-config, but that's probably tricky for your case: https://github.com/llvm/llvm-project/blob/64f0681e97c6046912dc0d80bc56709f72045338/llvm/lib/Support/CMakeLists.txt#L297-L298. llvm-config has been largely broken in various ways, particularly on macOS, for a while, e.g. llvm/llvm-project#39599. The CMake config has however always worked.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.