Re: [PATCH v2 0/3] detect-compiler: clang updates

From: Jeff King <peff@peff.net>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: "Junio C Hamano" <gitster@pobox.com>,
	git@vger.kernel.org,
	"Carlo Marcelo Arenas Belón" <carenas@gmail.com>
Subject: Re: [PATCH v2 0/3] detect-compiler: clang updates
Date: Sat, 7 Aug 2021 10:40:14 -0400	[thread overview]
Message-ID: <YQ6bTm6DxeJLhmeA@coredump.intra.peff.net> (raw)
In-Reply-To: <8735rlz5r2.fsf@evledraar.gmail.com>

On Sat, Aug 07, 2021 at 04:26:33PM +0200, Ævar Arnfjörð Bjarmason wrote:

> > That would probably be better. I would be curious to hear from somebody
> > with a mac if this technique gives more sensible version numbers for the
> > Apple-clang compiler.
> 
> It does, on the gcc304 box on the gccfarm (recent apple M1 Mac Mini):
> 
>     avar@minimac ~ % uname -a
>     Darwin minimac.moose.housegordon.com 20.4.0 Darwin Kernel Version 20.4.0: Thu Apr 22 21:46:41 PDT 2021; root:xnu-7195.101.2~1/RELEASE_ARM64_T8101 arm64    
>     avar@minimac ~ % clang --version
>     Apple clang version 12.0.5 (clang-1205.0.22.9)
>     Target: arm64-apple-darwin20.4.0
>     Thread model: posix
>     InstalledDir: /Library/Developer/CommandLineTools/usr/bin
> 
>     avar@minimac ~ % cat >f  
>     GNUC=__GNUC__
>     GNUC_MINOR=__GNUC_MINOR__
>     GNUC_PATCHLEVEL=__GNUC_PATCHLEVEL__
>     clang=__clang__
>     clang_major=__clang_major__
>     clang_minor=__clang_minor__
>     clang_patchlevel=__clang_patchlevel__
>     
>     ^C
> 
>     avar@minimac ~ % clang -E - <f
>     # 1 "<stdin>"
>     # 1 "<built-in>" 1
>     # 1 "<built-in>" 3
>     # 384 "<built-in>" 3
>     # 1 "<command line>" 1
>     # 1 "<built-in>" 2
>     # 1 "<stdin>" 2
>     GNUC=4
>     GNUC_MINOR=2
>     GNUC_PATCHLEVEL=1
>     clang=1
>     clang_major=12
>     clang_minor=0
>     clang_patchlevel=5

Hmm, now I'm really confused, though. Is that really clang 12 (for which
there is no 12.0.5; 12.0.1 is the latest version, shipped in July)? Or
is it XCode 12, shipping with LLVM 11, according to the table in:

  https://en.wikipedia.org/wiki/Xcode#Xcode_11.x_-_13.x_(since_SwiftUI_framework)

(sorry, there are actually _two_ tables with that same anchor on the
page; the one you want is the second one, under "Toolchain versions").

The distinction does not matter for our script (where we only care about
"clang4" and up). I guess the most relevant test would be to get XCode
8.x and see what it says. I expect it to claim "clang 8.1.0" or similar,
but actually be clang-3. And therefore not support
-Wtautological-constant-out-of-range-compare.

If we can't get easily get hold of such a platform, then maybe that is a
good indication that this conversation is too academic for now, and we
should wait until somebody wants to add a more recent version-specifier
to config.mak.dev. ;)

-Peff