From: Jakub Jelinek <jakub@redhat.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Richard Biener <richard.guenther@gmail.com>,
gcc-patches@gcc.gnu.org,
Alexander Monakov <amonakov@ispras.ru>
Subject: Re: [PATCH 0/2] Introduce gcc_qsort
Date: Fri, 11 May 2018 11:17:00 -0000 [thread overview]
Message-ID: <20180511104354.GO8577@tucnak> (raw)
In-Reply-To: <20180511102905.GC17342@gate.crashing.org>
On Fri, May 11, 2018 at 05:29:05AM -0500, Segher Boessenkool wrote:
> Such a comparator will still work with temporary arrays if both elements
> are always in the same temp array (in deterministic order, etc.) array; but
> it won't work if the comparator did e.g.
>
> return (r1 - reload_order) - (r2 - reload_order);
>
> (it would be undefined behaviour, to start with).
Yeah, UB, but likely would still "work".
What wouldn't work is if a comparator assumes certain sizes of the array
and e.g. stores the difference r1 - reload_order in char/short/int
because all callers guarantee that nmemb * size fits into such types.
Jakub
prev parent reply other threads:[~2018-05-11 10:44 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-10 15:57 Alexander Monakov
2018-05-10 15:57 ` [PATCH 2/2] gcc_qsort: build system changes Alexander Monakov
2018-05-11 9:32 ` Richard Biener
2018-05-10 17:01 ` [PATCH 1/2] gcc_qsort: source code changes Alexander Monakov
2018-05-10 17:01 ` David Malcolm
2018-05-10 17:44 ` Richard Biener
2018-05-10 18:08 ` Alexander Monakov
2018-05-10 18:57 ` DJ Delorie
2018-05-11 12:03 ` Richard Biener
2018-05-11 13:12 ` Alexander Monakov
2018-05-13 23:56 ` H.J. Lu
2018-05-14 8:44 ` Alexander Monakov
2018-05-14 9:08 ` Richard Biener
2018-05-10 17:35 ` [PATCH 0/2] Introduce gcc_qsort Jakub Jelinek
2018-05-10 17:48 ` Alexander Monakov
2018-05-10 17:43 ` Richard Biener
2018-05-10 17:57 ` Alexander Monakov
2018-05-11 10:35 ` Segher Boessenkool
2018-05-11 10:44 ` Alexander Monakov
2018-05-11 12:00 ` Segher Boessenkool
2018-05-11 12:16 ` Alexander Monakov
2018-05-11 12:52 ` Segher Boessenkool
2018-05-11 16:54 ` Eric Botcazou
2018-05-11 11:17 ` Jakub Jelinek [this message]
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