compiler detection on macOS seems to be incorrect

[xrisk]

BPO	44093
Nosy	@ronaldoussoren, @ned-deily, @xrisk
PRs	bpo-43109: Fix --with-lto configure option on macOS #26341

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/ned-deily'
closed_at = None
created_at = <Date 2021-05-10.03:01:36.707>
labels = ['3.7', '3.8', '3.9', 'build', 'OS-mac', 'type-bug', '3.10', '3.11']
title = 'compiler detection on macOS seems to be incorrect'
updated_at = <Date 2021-05-25.02:05:34.966>
user = 'https://github.com/xrisk'

bugs.python.org fields:

activity = <Date 2021-05-25.02:05:34.966>
actor = 'ned.deily'
assignee = 'ned.deily'
closed = False
closed_date = None
closer = None
components = ['Build', 'macOS']
creation = <Date 2021-05-10.03:01:36.707>
creator = 'xrisk'
dependencies = []
files = []
hgrepos = []
issue_num = 44093
keywords = ['patch']
message_count = 1.0
messages = ['393346']
nosy_count = 3.0
nosy_names = ['ronaldoussoren', 'ned.deily', 'xrisk']
pr_nums = ['26341']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue44093'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10', 'Python 3.11']

[xrisk]

On macOS devices, the configure script seems to always detect gcc, even though Apple does not ship with gcc — the gcc binary is simply a wrapper around clang (probably llvm-gcc?)

I believe the issue is with these lines.

cpython/configure.ac

Lines 630 to 635 in 8e8307d

	if test -n "`"$found_gcc" --version | grep llvm-gcc`"
	then
	AC_MSG_NOTICE([Detected llvm-gcc, falling back to clang])
	CC="$found_clang"
	CXX="$found_clang++"
	fi

Concretely, gcc —-version produces this on my computer:

$ gcc --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/4.2.1
Apple clang version 12.0.5 (clang-1205.0.22.9)
Target: x86_64-apple-darwin20.4.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

Perhaps an additional check for “clang” would solve the issue.

[furkanonder]

@ned-deily The issue seems to be solved. We can close the issue.

[ned-deily]

The issue seems to be solved. We can close the issue.

Perhaps I don't understand the desired result but it doesn't look solved to me. In particular, the test:

if test -n "`"$found_gcc" --version | grep llvm-gcc`" 

fails because compilers provided by current versions of Apple's Xcode or Command Line Tools no longer include the string llvm-gcc in their reported versions:

$ gcc --version
Apple clang version 14.0.3 (clang-1403.0.22.14.1)
Target: x86_64-apple-darwin22.4.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

[erlend-aasland]

Superseded by #110577.

Let's continue the discussion over there.

See also:

• configure.ac: using $CC to check compiler names may result in erroneous judgements #96398