[m-rev.] for review: Make gcc and clang version checks more robust.

[Peter Wang]

On Wed, 20 Dec 2023 14:54:52 +1100 Julien Fischer <jfischer at opturion.com> wrote:
> 
> On Tue, 19 Dec 2023, Peter Wang wrote:
> 
> > {x86_64,i686}-w64-mingw32-gcc -dumpfullversion on Debian 12
> > reports "12-win32", which the MERCURY_GCC_VERSION macro failed
> > to parse, as it expected a minor version to be present.
> 
> Really? Whose idea was that?!? That isn't the documented behaviour
> of that option.

I can't make sense of Debian packaging, but I suspect that's where to
look.

> > m4/mercury.m4:
> >    In the MERCURY_GCC_VERSION macro:
> >      - simplify calling $CC -dumpfullversion or $CC -dumpversion
> >      - trim any suffix following a hyphen in the raw gcc version output
> >      - set major/minor/patchlevel fields containing anything
> >        other than a sequence of decimal digits to "u"
> >      - use $() syntax for command substitutions
> >
> >    Modify the MERCURY_CLANG_VERSION macro in a similar way.
> 
> That's fine.

I shouldn't have added quotes around $CC, in case CC includes options
(which is more likely than the path to the C compiler containing spaces,
on Unix at least).

Thanks.

Peter