Re: Breakage (?) in configure and git_vsnprintf()

From: Jeff King <peff@peff.net>
Date: Dec 12, 2011, 08:10 UTC
Message-ID: <20111212081019.GA17725@sigill.intra.peff.net>
In-Reply-To: <4EE5B123.2030708@viscovery.net>

On Mon, Dec 12, 2011 at 08:45:39AM +0100, Johannes Sixt wrote:

Show 11 quoted lines

> Am 12/12/2011 7:43, schrieb Jeff King:
> > I'll leave the issue of "-std=c89" triggering SNPRINTF_RETURNS_BOGUS to
> > people who know and care about autoconf. My gut is to say "don't do
> > that".
> 
> Right. But Michael's problem was actually that SNPRINTF_RETURNS_BOGUS was
> set incorrectly; his system has a working snprintf (or so I assume). The
> reason for the failure is that ./configure's test program produced a
> warning, and that warning was turned into an error due to -Werror. Without
> -Werror, the test program would have compiled successfully, and the
> working snprintf would have been detected.

Right, I understand that. But he has given a set of options that shouldn't compile git at all (he tells the compiler not to use snprintf via -std=c89, but we require that it exists, because even our git_vsnprintf wrapper uses the underlying system vsnprintf).

So yes, the configure script is broken to detect the situation as SNPRINTF_RETURNS_BOGUS and not "this platform doesn't have snprintf at all"[1]. But I'm saying that the "we do not have snprintf at all" case is not all that interesting: git needs it. So I'm not sure compiling with -std=c89 really makes sense[2].

If somebody wants to make the configure script more accurate, I certainly don't want to stop them. I'm just not sure it is worth anybody's time in this case.

-Peff

[1] Yes, obviously we do actually have it, but it is somewhat a fluke
    that it works. We tell the compiler during the compile phase that we
    don't have it, but then during the link phase it is magically
    available in libc.

[2] I can convince git to compile on recent Linux with gcc using
    CFLAGS='-std=c89 -Dinline='.  Turning on "-Wall -Werror" doesn't
    work because all of the inline functions appear to be unused
    statics.  But if I understand Michael's problem correctly, wouldn't
    we be missing the prototype for snprintf, which could cause subtle
    errors?