Date: Tue, 13 Mar 2007 13:21:58 -0300 From: Ricardo Nabinger Sanchez <rnsanchez@wait4.org> To: Maxime Henrion <mux@FreeBSD.org> Cc: freebsd-bugs@FreeBSD.ORG, freebsd-current@FreeBSD.ORG Subject: Re: Bad gcc -O optimization cause core dump. What to do? Message-ID: <20070313132158.7368d186.rnsanchez@wait4.org> In-Reply-To: <20070313140632.GK65356@elvis.mu.org> References: <20070313121106.GA96293@nagual.pp.ru> <20070313101312.71d35c32.rnsanchez@wait4.org> <20070313140632.GK65356@elvis.mu.org>
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On Tue, 13 Mar 2007 15:06:32 +0100
Maxime Henrion <mux@FreeBSD.org> wrote:
> > Given that this is not what the user asked (replacing printf with puts), I
> > consider this a bug. GCC made its assumption, and it was incorrect--it's
> > not user's fault.
>
> GCC can do whatever it wants here, even printing "foobar42", because the
> C standard says that passing a NULL pointer to a %s format will yield
> undefined behaviour. It *is* user's fault to have passed NULL to
> printf() in the first place.
>
> So, while we could argue that GCC's behaviour here is useless, annoying,
> etc, this just can't be called a bug in GCC. As a side note, these
> "optimizations" are in place since a *long* time now.
... Considered until now. :)
Honestly, I wasn't aware of these specific issues (detail in the C standard +
gcc builtin printf optimization), and that's surely _my_ fault, not gcc's.
Sorry for the (useless) noise. Thank you (and DES) for pointing this out.
--
Ricardo Nabinger Sanchez <rnsanchez@{gmail.com,wait4.org}>
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