Local build is broken on macOS

[mofeing]

Referencing EnzymeAD/Reactant.jl#191

While trying to build #178 in macOS aarch64, I encountered the following error:

ERROR: /private/var/tmp/_bazel_mofeing/348146763cd9e75f8b24f7326c7da0a0/external/enzyme_ad/BUILD:58:10: Linking external/enzyme_ad/enzymexlamlir-tblgen [for tool] failed: (Exit 1): cc_wrapper.sh failed: error executing command (from target @enzyme_ad//:enzymexlamlir-tblgen) 
  (cd /private/var/tmp/_bazel_mofeing/348146763cd9e75f8b24f7326c7da0a0/sandbox/darwin-sandbox/610/execroot/__main__ && \
  exec env - \
    PATH='/Users/mofeing/Library/Caches/bazelisk/downloads/sha256/c6b6dc17efcdf13fba484c6fe0b6c3361b888ae7b9573bc25a2dbe8c502448eb/bin:/opt/homebrew/bin:/opt/homebrew/Cellar/pyenv-virtualenv/1.2.4/shims:/Users/mofeing/.pyenv/shims:/opt/homebrew/bin:/opt/homebrew/sbin:/opt/homebrew/opt/llvm/bin:/Applications/SuperCollider.app/Contents/MacOS:/Users/mofeing/.cargo/bin:/opt/homebrew/Caskroom/supercollider/3.13.0/SuperCollider.app/Contents/Resources:/opt/homebrew/opt/molten-vk/bin:/Users/mofeing/.local/bin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/opt/X11/bin:/Library/Apple/usr/bin:/Applications/Little Snitch.app/Contents/Components:/Applications/quarto/bin' \
    PWD=/proc/self/cwd \
  external/local_config_cc/cc_wrapper.sh @bazel-out/darwin_arm64-opt-exec-50AE0418/bin/external/enzyme_ad/enzymexlamlir-tblgen-2.params)
# Configuration: e0577b931c3d1306f5dfb647be2c29e19ef2a3f534787952d766fd2b735e74f6
# Execution platform: @local_execution_config_platform//:platform

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
clang: error: invalid linker name in argument '-fuse-ld=/opt/homebrew/opt/llvm/bin/ld64.lld'
Target //:libReactantExtra.so failed to build
INFO: Elapsed time: 135.791s, Critical Path: 20.59s
INFO: 2227 processes: 1622 internal, 605 darwin-sandbox.
FAILED: Build did NOT complete successfully

This bug was not introduced in #178 because there are no changes in the build system. Bisecting the repo, I've found out that this bug was introduced in 00b4d69

@wsmoses no flag was modified in that commit, but the Enzyme-JAX commit was updated from 4eeaef0 to 9f93d68, and the erroring target is external/enzyme_ad/enzymexlamlir-tblgen so most probably the bug origins there.

[mofeing]

@wsmoses it is failing because it seems that LLVM 19, installed through Homebrew, no longer provides the ld64.lld binary. What version does it appear if you do brew info llvm?

I've tried uninstalling it and using the llvm@17 recipe but it's not detecting it and it's still searching on /opt/homebrew/opt/llvm/bin. I can't find where that -fuse-ld flag is being set. Would you mind pointing it to me please?

[mofeing]

Homebrew now packages LLD (and ld64.lld) in another formula, so all you have to do is

brew install lld

and bazel should point to /opt/homebrew/opt/lld/bin/ld64.lld instead... but don't know how to change that @wsmoses

[wsmoses]

Oh that's unfortunate. Not sure but can try to investigate later.

In the meantime if you add the symlink yourself can you build so you're unblocked