Re: AC_PROG_CC: how to distinguish clnag from gcc?

[Paul Eggert]

On 2/7/21 11:46 PM, Sébastien Hinderer wrote:
> Did you notice important changes in the supported warnings between
> different versions of the same compiler?
>
> Are there many warnings in common between (at least one version of)
> clang and (at least one version of) gcc, actually?

The short answers to those two questions are "yes" and "yes".

I don't know of anybody who's come up with a comprehensive list of which 
compiler versions support which warnings correctly. Such a list would be 
tricky to do, as some warnings imply others, some warnings are 
language-dependent, and the warning dependencies can also change from 
version to version. At Gnulib we gave up trying to keep track of all the 
warnings (even though we were just doing GCC, not clang) and are 
currently using only the warnings listed here:

https://git.savannah.gnu.org/cgit/gnulib.git/tree/m4/manywarnings.m4
https://git.savannah.gnu.org/cgit/gnulib.git/tree/m4/manywarnings-c++.m4

with further documentation here:

https://git.savannah.gnu.org/cgit/gnulib.git/tree/build-aux/gcc-warning.spec