Re: AC_LANG_PROGRAM(C): function 'main' without prototype

[Ralf Wildenhues]

* Stepan Kasal wrote on Wed, Jun 25, 2008 at 06:26:56PM CEST:
> On Tue, Jun 24, 2008 at 08:14:44PM +0200, Nico R. wrote:
> > AC_LANG_PROGRAM(C) in c.m4 from autoconf:
> > Shouldn’t the line
> >   main ()
> > be
> >   main (void)
> > instead?
> 
> I admit I'm not sure about this.  The change would immediately break
> K&R compilers but they are no longer in the target set anyway.
> Let's wait for comments from those who know better. ;-)

Hehe, I don't know better, but I'll take it as "those who think they
should post their opinion anyway".  ;->

IIRC, so far Autoconf still mostly supports pre-C89 compilers, even
if maybe not fully.  This would be a definite step away from that.
(Stating this without having a strong opinion on it; I simply don't
know how relevant that is to users.)

> > If CFLAGS contains '-Werror’
> 
> Well, the configure collects literally bits of information about the
> platform.  The bit is 0 or 1, depending on whether the compilation
> (link) failed or not.  Using -Werror may skew some results.

Exactly.  We cannot get all macros warning-free, even when limiting
ourselves to GCC's warnings.  Some of Autoconf's macros necessarily
rely on dubious constructs.

> Generally, while -Werror during "make" makes you more safe, -Werror
> at configure time exposes you to extra risk.
> 
> Perhaps we should do something about it.  Perhaps ./configure should
> detect -Werror in CFLAGS (and other *FLAGS) and bail out with an
> error message.

I have already forgotten again whether the proposed AC_*_WERROR
improvements also addressed this case: that we have a macro for
which we would like to temporarily turn off -Werror, iff it had
been passed.  Even if we had such functionality, though, I'm not
sure we would want to use it in the above case.

Cheers,
Ralf