[MPlayer-dev-eng] [PATCH] Add mp_strings.c with mp_asprintf function.

[Reimar Döffinger]

On Thu, Jan 27, 2011 at 09:11:25PM +0100, Clément Bœsch wrote:
> > Sorry for the late reply. What I would expect might happen is that in
> > C99 mode asprintf is not available (and we certainly don't want to
> > have yet another thing that requires _GNU_SOURCE everywhere), so
> > configure detection will fail. However linking will fail as well,
> > since then asprintf is defined both in the libc and in MPlayer.
> 
> I'm not sure I get the difference between the compilation test made at
> ./configure and the way mplayer is built; the asprintf test does not check
> if we have _GNU_SOURCE defined, it try to compile a source code using it.
> Or did I missed something again?

I realize it all doesn't make much sense, and I should just say:
to get asprintf we need to define _GNU_SOURCE. But we absolutely
should avoid this in any way possible. So even when we use asprintf
we should do so via a wrapper, so that we have to define _GNU_SOURCE
on in the one file where the wrapper is implemented.
Just in case you are curious, my original thoughts were:
Well, without _GNU_SOURCE it is not in the header. Ideally the test should
fail (I just realize this probably is not the case) then since without a
declaration it cannot be used safely, particularly on 64 bit systems.
Thus we use our own implementation instead. That would be a bit silly
in itself, since we would be using it always and never a system one.
Either way, linking fails because that has the same name as a symbol in the libc.
So we'd be stuck with defining _GNU_SOURCE everywhere where we used
asprintf