llvm-ar not found when building with clang-tidy

[davidzchen]

Description of the bug:

Building Carbon with the clang-tidy configuration results in an error reporting that "llvm-ar not found in PATH or adjacent to clang"

What did you do, or what's a simple way to reproduce the bug?

Fresh check-out of the repo and then run:

bazel build --config=clang-tidy //...

What did you expect to happen?

The build to succeed.

What actually happened?

$ bazel build --config=clang-tidy //...
Starting local Bazel server and connecting to it...
WARNING: ignoring JAVA_TOOL_OPTIONS in environment.
INFO: Invocation ID: bd9757e5-f9b5-4af3-b441-9582d5293a96
INFO: Repository _main~clang_toolchain_extension~bazel_cc_toolchain instantiated at:
  <builtin>: in <toplevel>
Repository rule configure_clang_toolchain defined at:
  /Users/dzc/Repos/github/OpenEmu/OpenEmu/carbon-language/carbon-lang/bazel/cc_toolchains/clang_configuration.bzl:229:44: in <toplevel>
ERROR: An error occurred during the fetch of repository '_main~clang_toolchain_extension~bazel_cc_toolchain':
   Traceback (most recent call last):
        File "/Users/dzc/Repos/github/OpenEmu/OpenEmu/carbon-language/carbon-lang/bazel/cc_toolchains/clang_configuration.bzl", line 202, column 17, in _configure_clang_toolchain_impl
                fail("`llvm-ar` not found in PATH or adjacent to clang")
Error in fail: `llvm-ar` not found in PATH or adjacent to clang
ERROR: <builtin>: fetching configure_clang_toolchain rule //:_main~clang_toolchain_extension~bazel_cc_toolchain: Traceback (most recent call last):
        File "/Users/dzc/Repos/github/OpenEmu/OpenEmu/carbon-language/carbon-lang/bazel/cc_toolchains/clang_configuration.bzl", line 202, column 17, in _configure_clang_toolchain_impl
                fail("`llvm-ar` not found in PATH or adjacent to clang")
Error in fail: `llvm-ar` not found in PATH or adjacent to clang
WARNING: Target pattern parsing failed.
ERROR: Skipping '//...': error loading package under directory '': no such package '@@_main~clang_toolchain_extension~bazel_cc_toolchain//': `llvm-ar` not found in PATH or adjacent to clang
ERROR: error loading package under directory '': no such package '@@_main~clang_toolchain_extension~bazel_cc_toolchain//': `llvm-ar` not found in PATH or adjacent to clang
INFO: Elapsed time: 6.924s
INFO: 0 processes.
ERROR: Build did NOT complete successfully
FAILED:
    Fetching repository @@bazel_features~; Patching repository

Any other information, logs, or outputs that you want to share?

No response

[jonmeow]

This is a common issue for os-provided llvm installs, particularly when you're using an older macos system install (from "/Users" I assume this is macos). See contribution tools for advice on installing llvm.

If that doesn't address your issue, please provide the output of these troubleshooting commands:

echo $CC
which clang
which clang-16
clang --version
grep llvm_bindir $(bazel info workspace)/bazel-execroot/external/bazel_cc_toolchain/clang_detected_variables.bzl

# If on macOS:
brew --prefix llvm

[chandlerc]

@justzh - Please keep comments on PRs and issues constructive and on-topic. I'm hiding yours, but you've had warnings now and so I will block if this continues.

Rapid-fire asking of questions, or speaking for the reporter isn't a constructive or appropriate use of issues.

[davidzchen]

Sorry for the delay. I followed the instructions at Contribution Tools but I am still getting the same error:

$ brew install \
  bazelisk \
  gh \
  llvm \
  [email protected] \
  pre-commit
---snipped---
$ pre-commit install
pre-commit installed at .git/hooks/pre-commit
$ bazel test //...:all
2024/04/07 15:34:48 Downloading https://releases.bazel.build/7.1.0/release/bazel-7.1.0-darwin-arm64...
Downloading: 61 MB out of 61 MB (100%)
Extracting Bazel installation...
Starting local Bazel server and connecting to it...
WARNING: ignoring JAVA_TOOL_OPTIONS in environment.
INFO: Invocation ID: 9f0eb370-661d-495e-8e64-61ba0554c834
INFO: Repository _main~clang_toolchain_extension~bazel_cc_toolchain instantiated at:
  <builtin>: in <toplevel>
Repository rule configure_clang_toolchain defined at:
  /Users/dzc/Repos/github/carbon-language/carbon-lang/bazel/cc_toolchains/clang_configuration.bzl:229:44: in <toplevel>
ERROR: An error occurred during the fetch of repository '_main~clang_toolchain_extension~bazel_cc_toolchain':
   Traceback (most recent call last):
        File "/Users/dzc/Repos/github/carbon-language/carbon-lang/bazel/cc_toolchains/clang_configuration.bzl", line 202, column 17, in _configure_clang_toolchain_impl
                fail("`llvm-ar` not found in PATH or adjacent to clang")
Error in fail: `llvm-ar` not found in PATH or adjacent to clang
ERROR: <builtin>: fetching configure_clang_toolchain rule //:_main~clang_toolchain_extension~bazel_cc_toolchain: Traceback (most recent call last):
        File "/Users/dzc/Repos/github/carbon-language/carbon-lang/bazel/cc_toolchains/clang_configuration.bzl", line 202, column 17, in _configure_clang_toolchain_impl
                fail("`llvm-ar` not found in PATH or adjacent to clang")
Error in fail: `llvm-ar` not found in PATH or adjacent to clang
ERROR: Skipping '//...:all': error loading package under directory '': no such package '@@_main~clang_toolchain_extension~bazel_cc_toolchain//': `llvm-ar` not found in PATH or adjacent to clang
ERROR: error loading package under directory '': no such package '@@_main~clang_toolchain_extension~bazel_cc_toolchain//': `llvm-ar` not found in PATH or adjacent to clang
INFO: Elapsed time: 2.995s
INFO: 0 processes.
ERROR: Build did NOT complete successfully
ERROR: Couldn't start the build. Unable to run tests

[davidzchen]

Outputs for the requested commands:

$ which $CC
# no output

$ which clang
/usr/bin/clang

$ which clang-16
clang-16 not found

$ clang --version
Apple clang version 15.0.0 (clang-1500.1.0.2.5)
Target: arm64-apple-darwin23.4.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

$ grep llvm_bindir $(bazel info workspace)/bazel-execroot/external/bazel_cc_toolchain/clang_detected_variables.bzl
INFO: Invocation ID: ce012800-43b0-4d82-b9f5-9ddb32bfb8fe
grep: /Users/dzc/Repos/github/carbon-language/carbon-lang/bazel-execroot/external/bazel_cc_toolchain/clang_detected_variables.bzl: No such file or directory

$ brew --prefix llvm
/opt/homebrew/opt/llvm

[jonmeow]

$ which clang
/usr/bin/clang

It looks like you need to add brew's llvm to your path, as described at https://github.com/carbon-language/carbon-lang/blob/trunk/docs/project/contribution_tools.md#macos:

# For `brew`, `gh`, and other tools:
export PATH="${HOME}/.brew/bin:${PATH}"
# For `llvm`:
export PATH="$(brew --prefix llvm)/bin:${PATH}"