RFC: Changing AC_PROG_CC to AC_PROG_CC_C99 in top level configure

[Alan Modra]

On Fri, Apr 30, 2021 at 03:48:00PM -0600, Jeff Law via Gcc-patches wrote:
> 
> On 4/30/2021 12:36 PM, Simon Marchi via Gcc-patches wrote:
> > On 2021-04-26 7:32 a.m., Nick Clifton via Gdb-patches wrote:> Hi Guys,
> > >    Given that gcc, gdb and now binutils are all now requiring C99 as a
> > >    minimum version of C, are there any objections to updating
> > >    configure.ac to reflect this ?
> > > 
> > > Cheers
> > >    Nick
> > > 
> > > diff --git a/configure.ac b/configure.ac
> > > index a721316d07b..59b4194fb24 100644
> > > --- a/configure.ac
> > > +++ b/configure.ac
> > > @@ -1278,7 +1278,7 @@ else
> > >     WINDMC_FOR_BUILD="\$(WINDMC)"
> > >   fi
> > > 
> > > -AC_PROG_CC
> > > +AC_PROG_CC_C99
> > >   AC_PROG_CXX
> > > 
> > >   # We must set the default linker to the linker used by gcc for the correct
> > Hi Nick,
> > 
> > I think this fix is obvious enough, I encourage you to push it, that
> > will fix the build failure many people get in opcodes/ppc-dis.c.  We'll
> > just remove the line later when we upgrade to Autoconf 2.71, as simple
> > as that.  For now we use 2.69.  If that matters, you have my OK for the
> > GDB side of things.
> 
> That works for me.  I'd just sent Alan the trivial patch to make ppc-dis.c
> compile again with C89, but if we're going to update configure.ac
> appropriately, then it wouldn't be needed.

Yes, I prefer the configure fix too.  If we state we require C99 in
binutils then we ought to be able to use C99..

Nick, does the configure.ac change also need to go in all subdirs, to
support people running make in say ld/ rather than running make in the
top build dir?

-- 
Alan Modra
Australia Development Lab, IBM