clang-tidy broken with llvm v19.1.3

[lukeshingles]

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

https://gist.github.com/lukeshingles/b1477f4b5eaf327af99940ec848213b4

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)?

clang-tidy is no longer finding system headers since the llvm 19.1.3 update (#196094)

What happened (include all command output)?

$ clang-tidy helloworld.cpp
4 warnings and 1 error generated.
Error while processing /Users/luke/test/helloworld.cpp.
warning: -lunwind: 'linker' input unused [clang-diagnostic-unused-command-line-argument]
warning: argument unused during compilation: '-L/opt/homebrew/opt/llvm/lib' [clang-diagnostic-unused-command-line-argument]
warning: argument unused during compilation: '-L/opt/homebrew/opt/llvm/lib/c++' [clang-diagnostic-unused-command-line-argument]
warning: argument unused during compilation: '-L/opt/homebrew/opt/llvm/lib/unwind' [clang-diagnostic-unused-command-line-argument]
helloworld.cpp:1:10: error: 'iostream' file not found [clang-diagnostic-error]
    1 | #include <iostream>
      |          ^~~~~~~~~~
Found compiler error(s).

What did you expect to happen?

Using llvm 19.1.2 formula, the output is:

$ clang-tidy helloworld.cpp
4 warnings generated.
warning: -lunwind: 'linker' input unused [clang-diagnostic-unused-command-line-argument]
warning: argument unused during compilation: '-L/opt/homebrew/opt/llvm/lib' [clang-diagnostic-unused-command-line-argument]
warning: argument unused during compilation: '-L/opt/homebrew/opt/llvm/lib/c++' [clang-diagnostic-unused-command-line-argument]
warning: argument unused during compilation: '-L/opt/homebrew/opt/llvm/lib/unwind' [clang-diagnostic-unused-command-line-argument]

(Some warnings but no error finding <iostream>).

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

// helloworld.cpp
#include <iostream>

int main() {
  std::cout << "Hello World!";
  return 0;
}

pip install compiledb
compiledb make helloworld
clang-tidy helloworld.cpp

[lukeshingles]

I get the same errors when I run clang-tidy from pip (latest version is 19.1.0) when brew llvm 19.1.3 is installed.

[carlocab]

Oh, that's annoying. Looks like clang-tidy does not use Clang config files.

As a workaround, try

xcrun clang-tidy helloworld.cpp

[Congyuwang]

Similar problem, but with clang. With 19.1.3, clang can't find stuff like #include<string>.

Now I'll have to manually add --sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk for things to work.

I wonder if this is as expected. Or what is the right way to fix this system-header-missing problem?

[lukeshingles]

For me, I didn’t have any problem compiling with clang++. Does my simple example compile?

[carlocab]

@Congyuwang, I can't reproduce your issue so I'll need to know:

• the output of your brew config
• the output of your brew doctor
• the output of ls -la /Library/Developer/CommandLineTools
• the exact steps needed to reproduce the failure you're seeing

[Bo98]

Looks like clang-tidy does not use Clang config files.

For the clang-tidy issue: looks like it's not resolving the config directory correctly:

$ /opt/homebrew/opt/llvm/bin/clang++ -v test.cpp
Homebrew clang version 19.1.3
Target: arm64-apple-darwin23.6.0
Thread model: posix
InstalledDir: /opt/homebrew/Cellar/llvm/19.1.3/bin
Configuration file: /opt/homebrew/etc/clang/arm64-apple-darwin23.cfg
System configuration file directory: /opt/homebrew/etc/clang
User configuration file directory: /Users/bo/.config/clang
 "/opt/homebrew/Cellar/llvm/19.1.3/bin/clang-19" -cc1 ...

$ /opt/homebrew/opt/llvm/bin/clang-tidy test.cpp
Homebrew clang version 19.1.3
Target: arm64-apple-darwin23.6.0
Thread model: posix
InstalledDir: 
System configuration file directory: ../../../../etc/clang
User configuration file directory: /Users/bo/.config/clang
ignoring nonexistent directory "../include/c++/v1"
ignoring nonexistent directory "/usr/include/c++/v1"
clang Invocation:
 "c++" "-cc1" ...

[carlocab]

For the clang-tidy issue: looks like it's not resolving the config directory correctly:

This seems to be why:

InstalledDir:

It doesn't know where the driver is, so it can't resolve the path to the config file.

[xakep8]

For the clang-tidy issue: looks like it's not resolving the config directory correctly:

This seems to be why:

InstalledDir:

It doesn't know where the driver is, so it can't resolve the path to the config file.

would it work to use a custom prefix flag with path while building to fix issue?

[carlocab]

would it work to use a custom prefix flag with path while building to fix issue?

Not quite, since InstalledDir is not populated by the build-time install prefix. For clang, this is populated here (and then printed here). clang-tidy needs to do something similar.

In any case, we also do set CMAKE_INSTALL_PREFIX when building, so not sure there is much more to do in that regard.

[Bo98]

LLVM is designed to be relocatable so it does not bake in install prefixes.

[carlocab]

@Congyuwang, I think your issue should have been fixed by #197410. You'll need to brew update && brew reinstall llvm to pick up the fix. (Or do brew update && brew postinstall llvm if you're only doing native builds.)

[Congyuwang]

@carlocab Not working. Running the following

main.c

int main() {
    return 0;
}

build.sh

eval "$(brew shellenv)"
export LLD=${HOMEBREW_PREFIX}/opt/lld/bin/ld64.lld
export CC=${HOMEBREW_PREFIX}/opt/llvm/bin/clang
${CC} -O3 --target=arm64-apple-macosx10.14 -fuse-ld=${LLD} -o main main.c -v

Run ./build.sh

We get

Homebrew clang version 19.1.3
Target: arm64-apple-macosx10.14
Thread model: posix
InstalledDir: /opt/homebrew/Cellar/llvm/19.1.3/bin
Configuration file: /opt/homebrew/etc/clang/arm64-apple-macosx10.14.cfg
System configuration file directory: /opt/homebrew/etc/clang
User configuration file directory: /Users/congyuwang/.config/clang
 "/opt/homebrew/Cellar/llvm/19.1.3/bin/clang-19" -cc1 -triple arm64-apple-macosx10.14.0 -Wundef-prefix=TARGET_OS_ -Werror=undef-prefix -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -dumpdir main- -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name main.c -mrelocation-model pic -pic-level 2 -mframe-pointer=non-leaf -ffp-contract=on -fno-rounding-math -funwind-tables=1 -fcompatibility-qualified-id-block-type-checking -fvisibility-inlines-hidden-static-local-var -fbuiltin-headers-in-system-modules -fdefine-target-os-macros -target-cpu apple-m1 -target-feature +zcm -target-feature +zcz -target-feature +v8.4a -target-feature +aes -target-feature +altnzcv -target-feature +ccdp -target-feature +complxnum -target-feature +crc -target-feature +dotprod -target-feature +fp-armv8 -target-feature +fp16fml -target-feature +fptoint -target-feature +fullfp16 -target-feature +jsconv -target-feature +lse -target-feature +neon -target-feature +pauth -target-feature +perfmon -target-feature +predres -target-feature +ras -target-feature +rcpc -target-feature +rdm -target-feature +sb -target-feature +sha2 -target-feature +sha3 -target-feature +specrestrict -target-feature +ssbs -target-abi darwinpcs -debugger-tuning=lldb -fdebug-compilation-dir=/Users/congyuwang/Projects/CppProjects/brew-clang-debug -target-linker-version 1115.7.3 -v -fcoverage-compilation-dir=/Users/congyuwang/Projects/CppProjects/brew-clang-debug -resource-dir /opt/homebrew/Cellar/llvm/19.1.3/lib/clang/19 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -internal-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/local/include -internal-isystem /opt/homebrew/Cellar/llvm/19.1.3/lib/clang/19/include -internal-externc-isystem /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include -O3 -ferror-limit 19 -stack-protector 1 -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fmax-type-align=16 -fcolor-diagnostics -vectorize-loops -vectorize-slp -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /var/folders/fc/bckw5h_s4c9fz9dlgltf7b840000gn/T/main-b0ef43.o -x c main.c
clang -cc1 version 19.1.3 based upon LLVM 19.1.3 default target arm64-apple-darwin24.1.0
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/local/include"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/System/Library/Frameworks"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /opt/homebrew/Cellar/llvm/19.1.3/lib/clang/19/include
End of search list.
 "/opt/homebrew/opt/lld/bin/ld64.lld" -demangle -lto_library /opt/homebrew/Cellar/llvm/19.1.3/lib/libLTO.dylib -dynamic -arch arm64 -platform_version macos 11.0.0 11.0.0 -syslibroot /Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk -mllvm -enable-linkonceodr-outlining -o main /var/folders/fc/bckw5h_s4c9fz9dlgltf7b840000gn/T/main-b0ef43.o -lSystem /opt/homebrew/Cellar/llvm/19.1.3/lib/clang/19/lib/darwin/libclang_rt.osx.a
ld64.lld: error: library not found for -lSystem
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Seems like MacOSX10.14.sdk is not found.

However, specifying --sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk compiles successfully.

[Congyuwang]

❯ ls /Library/Developer/CommandLineTools/SDKs/
MacOSX.sdk     MacOSX12.1.sdk MacOSX12.3.sdk MacOSX14.5.sdk MacOSX14.sdk   MacOSX15.1.sdk MacOSX15.sdk

I only have the above. MacOS 15.1, Xcode 16.1. There is no MacOSX10.14.sdk.

Whereas we have

❯ cat /opt/homebrew/etc/clang/arm64-apple-macosx10.14.cfg
--sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk