Bootstraping GCC 13.2 with llvm/clang 17?

[ilg-ul]

Output of brew config

HOMEBREW_VERSION: 4.2.17
ORIGIN: https://github.com/Homebrew/brew.git
HEAD: 0476c2e5e4f02b409084553896340b2f4ab3352e
Last commit: 3 days ago
Core tap JSON: 08 Apr 12:16 UTC
Core cask tap JSON: 08 Apr 12:16 UTC
HOMEBREW_PREFIX: /Users/ilg/.local/homebrew/hb
HOMEBREW_REPOSITORY: /Users/ilg/.local/homebrew/hb
HOMEBREW_CELLAR: /Users/ilg/.local/homebrew/hb/Cellar
HOMEBREW_CASK_OPTS: []
HOMEBREW_MAKE_JOBS: 12
HOMEBREW_NO_EMOJI: set
Homebrew Ruby: 3.1.4 => /Users/ilg/.local/homebrew/hb/Library/Homebrew/vendor/portable-ruby/3.1.4/bin/ruby
CPU: dodeca-core 64-bit kabylake
Clang: 15.0.0 build 1500
Git: 2.44.0 => /Users/ilg/.local/homebrew/hb/bin/git
Curl: 8.4.0 => /usr/bin/curl
macOS: 14.3.1-x86_64
CLT: 15.1.0.0.1.1700200546
Xcode: N/A

Output of brew doctor

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: Some installed formulae are deprecated or disabled.
You should find replacements for the following formulae:
  [email protected]

Warning: Unbrewed dylibs were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected dylibs:
  /usr/local/lib/libPDFNetC.dylib
  /usr/local/lib/libusb-1.0.0.dylib
  /usr/local/lib/libusb-1.0.dylib

Warning: Your Homebrew's prefix is not /usr/local.

Many of Homebrew's bottles (binary packages) can only be used with the default prefix.
Consider uninstalling Homebrew and reinstalling into the default prefix.
It is expected behaviour that some formulae will fail to build in this unsupported configuration.
It is expected behaviour that Homebrew will be buggy and slow.
Do not create any issues about this on Homebrew's GitHub repositories.
Do not create any issues even if you think this message is unrelated.
Any opened issues will be immediately closed without response.
Do not ask for help from Homebrew or its maintainers on social media.
You may ask for help in Homebrew's discussions but are unlikely to receive a response.
Try to figure out the problem yourself and submit a fix as a pull request.
We will review it but may or may not accept it.


Warning: Homebrew's "sbin" was not found in your PATH but you have installed
formulae that put executables in /Users/ilg/.local/homebrew/hb/sbin.
Consider setting your PATH for example like so:
  echo 'export PATH="/Users/ilg/.local/homebrew/hb/sbin:$PATH"' >> ~/.zshrc

Description of issue

I'm trying to build GCC 13.2 with the latest clang available in Homebrew (17.0.6) and the build fails with multiple errors, but apparently the cause is a C++ header file:

In file included from /Users/ilg/Work/xpack-dev-tools-build/gcc-13.2.0-2/darwin-x64/sources/gcc-13.2.0/gcc/cp/mapper-client.cc:31:
In file included from /Users/ilg/Work/xpack-dev-tools-build/gcc-13.2.0-2/darwin-x64/sources/gcc-13.2.0/gcc/system.h:227:
In file included from /Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/map:2529:
In file included from /Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/functional:526:
In file included from /Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/__functional/boyer_moore_searcher.h:27:
In file included from /Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/vector:321:
In file included from /Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/__format/formatter_bool.h:20:
In file included from /Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/__format/formatter_integral.h:32:
In file included from /Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/locale:202:
/Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/__locale:657:37: error: expected ';' at end of declaration list
  657 |     char_type toupper(char_type __c) const
      |                                     ^
/Users/ilg/.local/homebrew/hb/Cellar/llvm/17.0.6_1/bin/../include/c++/v1/__locale:663:48: error: too many arguments provided to function-like macro invocation
...

rm gcc.pod
make[2]: *** [all-stage1-gcc] Error 2
make[1]: *** [stage1-bubble] Error 2
make: *** [all] Error 2

I tried exactly the same build script with llvm@16 and the build passed.

I'm using an Intel macOS 14.3.1 and CLT 15.1. The GCC configuration has an explicit --enable-bootstrap and the same patches as used by Homebrew GCC 13.2.

I reported this issue first to iains/gcc-13-branch#17, but the maintainer wishes Homebrew to confirm the issue.

@fxcoudert?

[fxcoudert]

GCC in Homebrew is built with Apple's clang. Use of different compilers (like LLVM 17) is not supported or tested on CI.

I believe this issue might be fixed by https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=68057560ff1fc0fb2df38c2f9627a20c9a8da5c5 and https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=e95ab9e60ce1d9aa7751d79291133fd5af9209d7