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List:       autoconf
Subject:    Re: AC_PROG_CC: how to distinguish clang from gcc?
From:       "David A. Wheeler" <dwheeler () dwheeler ! com>
Date:       2021-02-05 16:40:47
Message-ID: 6E8DB7F8-0AAF-4855-B11C-C6F4F9194EDD () dwheeler ! com
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> On Feb 5, 2021, at 9:51 AM, Todd C. Miller <Todd.Miller@sudo.ws> wrote:
> 
> On Fri, 05 Feb 2021 15:42:28 +0100, =?utf-8?Q?S=C3=A9bastien?= Hinderer wrote:
> 
>> It seems AC_PROG_CC wrongly believes clang is gcc and that may cause problems
>> when clang is passed a warning which is only supposrted by gcc, as is
>> the case e.g. for -Wno-stringop-truncation.
> 
> clang also defines __GNUC__ and the related defines, which is why
> it is identified as gcc.
> 
>> Is there a recommended way to determine for sure from a configure script
>> whether the detected C compiler is clang or gcc?

I would *discourage* trying to figure out if a C compiler is gcc or clang.
Instead, create separate detectors for whatever you're looking for.

The gcc & clang groups coordinate with each other; they try to provide the same
flags & API for the same functionality, and occasionally copy from each other.
So trying to detect "do this if GCC" is generally wrong; clang may have that interface & functionality
when someone compiles the code.

--- David A. Wheeler


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