Re: AC_PROG_CC: how to distinguish clang from gcc?

[David A. Wheeler]

> 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