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From: "ian at airs dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/30475] assert(int+100 > int) optimized away
Date: Mon, 22 Jan 2007 20:16:00 -0000	[thread overview]
Message-ID: <20070122201633.5121.qmail@sourceware.org> (raw)
In-Reply-To: <bug-30475-3511@http.gcc.gnu.org/bugzilla/>



------- Comment #49 from ian at airs dot com  2007-01-22 20:16 -------
In the C language standard "undefined behaviour" meants that the compiler can
do anything at all.  It means that the program is specifically undefined.

When you say that the compiler should not eliminate the test because the value
does turn out to be negative, you appear to be assuming that signed overflow is
actually "implementation defined behaviour."  That would have the property that
you are after.

When you say that -fwrapv makes the code faster, I don't know which benchmarks
you are relying on.  Other people have demonstrated that -fwrapv slows down the
well-known SPEC benchmark.

I've written some comments in the appropriate place: the gcc mailing list:
http://gcc.gnu.org/ml/gcc/2007-01/msg00885.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30475


  parent reply	other threads:[~2007-01-22 20:16 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-15 19:43 [Bug c/30475] New: " felix-gcc at fefe dot de
2007-01-15 19:46 ` [Bug c/30475] " felix-gcc at fefe dot de
2007-01-15 19:47 ` pinskia at gcc dot gnu dot org
2007-01-15 19:50 ` felix-gcc at fefe dot de
2007-01-15 19:57 ` felix-gcc at fefe dot de
2007-01-15 20:04 ` pinskia at gcc dot gnu dot org
2007-01-16  4:47 ` pinskia at gcc dot gnu dot org
2007-01-16  7:00 ` pluto at agmk dot net
2007-01-16  7:24 ` gcc at mailinator dot com
2007-01-17 13:55 ` felix-gcc at fefe dot de
2007-01-17 14:26 ` rguenth at gcc dot gnu dot org
2007-01-17 14:31 ` rguenth at gcc dot gnu dot org
2007-01-17 15:21 ` felix-gcc at fefe dot de
2007-01-17 16:32 ` rguenth at gcc dot gnu dot org
2007-01-17 16:37 ` felix-gcc at fefe dot de
2007-01-17 16:54 ` erdgeist-gcc at erdgeist dot org
2007-01-17 16:57 ` pinskia at gcc dot gnu dot org
2007-01-17 17:03 ` felix-gcc at fefe dot de
2007-01-17 17:06 ` rguenth at gcc dot gnu dot org
2007-01-17 17:12 ` pinskia at gcc dot gnu dot org
2007-01-17 17:14 ` amacleod at redhat dot com
2007-01-17 17:20 ` felix-gcc at fefe dot de
2007-01-17 17:42 ` pinskia at gcc dot gnu dot org
2007-01-17 18:23 ` felix-gcc at fefe dot de
2007-01-17 18:43 ` pinskia at gcc dot gnu dot org
2007-01-17 19:04 ` felix-gcc at fefe dot de
2007-01-17 19:18 ` pinskia at gcc dot gnu dot org
2007-01-18 15:20 ` felix-gcc at fefe dot de
2007-01-18 15:24 ` felix-gcc at fefe dot de
2007-01-18 17:36 ` pinskia at gcc dot gnu dot org
2007-01-21  8:58 ` pinskia at gcc dot gnu dot org
2007-01-21 12:23 ` andreas at andreas dot org
2007-01-21 12:49 ` andreas at andreas dot org
2007-01-21 13:53 ` felix-gcc at fefe dot de
2007-01-21 16:31 ` pinskia at gcc dot gnu dot org
2007-01-21 17:30 ` andreas at andreas dot org
2007-01-21 17:47 ` felix-gcc at fefe dot de
2007-01-21 18:16 ` pluto at agmk dot net
2007-01-21 19:46 ` rguenth at gcc dot gnu dot org
2007-01-21 20:14 ` pinskia at gcc dot gnu dot org
2007-01-21 21:52 ` tromey at gcc dot gnu dot org
2007-01-22  2:18 ` felix-gcc at fefe dot de
2007-01-22  2:27 ` pinskia at gcc dot gnu dot org
2007-01-22 13:02 ` felix-gcc at fefe dot de
2007-01-22 17:15 ` pinskia at gcc dot gnu dot org
2007-01-22 18:26 ` steven at gcc dot gnu dot org
2007-01-22 18:33 ` pinskia at gcc dot gnu dot org
2007-01-22 18:36 ` andreas at andreas dot org
2007-01-22 19:50 ` felix-gcc at fefe dot de
2007-01-22 20:16 ` ian at airs dot com [this message]
2007-01-22 22:27 ` pinskia at gcc dot gnu dot org
2007-01-22 23:10 ` andreas at andreas dot org
2007-01-23  0:46 ` kargl at gcc dot gnu dot org
2007-03-08  1:03 ` js at linuxtv dot org
2007-03-08  1:14 ` pinskia at gcc dot gnu dot org
2007-03-08 16:23 ` js at linuxtv dot org
     [not found] <bug-30475-4@http.gcc.gnu.org/bugzilla/>
2014-02-16 10:00 ` jackie.rosen at hushmail dot com
2021-01-05 12:26 ` daniel.marjamaki at gmail dot com
2021-01-05 12:56 ` daniel.marjamaki at gmail dot com
2021-01-05 13:30 ` jakub at gcc dot gnu.org
2021-01-05 13:37 ` jakub at gcc dot gnu.org
2021-01-06 10:37 ` daniel.marjamaki at gmail dot com

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