From: Markus Trippelsdorf <markus@trippelsdorf.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org,
mingo@kernel.org, linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/urgent] x86/tools: Fix gcc-7 warning in relocs.c
Date: Tue, 20 Dec 2016 11:00:56 +0100 [thread overview]
Message-ID: <20161220100056.GA289@x4> (raw)
In-Reply-To: <c6f83231-9847-3f41-6743-325248ffc451@zytor.com>
On 2016.12.20 at 01:30 -0800, H. Peter Anvin wrote:
> I'd strongly prefer a non-data-dependent solution, specifically adding
> at the top of sort_relocs():
>
> if (!r->count)
> return;
>
> However, by my reading of the C and POSIX standards, this is a gcc
> error: qsort() should do nothing if the count is zero.
No, it is invoking undefined behavior.
Notice the nonnull attribute in /usr/include/stdlib.h:
739 /* Sort NMEMB elements of BASE, of SIZE bytes each,
740 using COMPAR to perform the comparisons. */
741 extern void qsort (void *__base, size_t __nmemb, size_t __size,
742 __compar_fn_t __compar) __nonnull ((1, 4));
But feel free to revert my patch and add your solution.
--
Markus
next prev parent reply other threads:[~2016-12-20 10:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-15 12:45 [PATCH] x86-64: Fix gcc-7 warning in relocs.c Markus Trippelsdorf
2016-12-19 10:56 ` [tip:x86/urgent] x86/tools: " tip-bot for Markus Trippelsdorf
2016-12-20 9:30 ` H. Peter Anvin
2016-12-20 10:00 ` Markus Trippelsdorf [this message]
2016-12-20 11:10 ` H. Peter Anvin
2016-12-20 11:51 ` Markus Trippelsdorf
2016-12-20 18:32 ` hpa
2016-12-20 19:31 ` Markus Trippelsdorf
2016-12-20 20:44 ` H. Peter Anvin
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