From: Nikos Chantziaras <realnc@arcor.de>
To: gentoo-amd64@lists.gentoo.org
Subject: [gentoo-amd64] Re: GCC-4.5.2 Has Serious Problems
Date: Fri, 01 Jul 2011 02:44:36 +0300 [thread overview]
Message-ID: <iuj1o7$o6s$2@dough.gmane.org> (raw)
In-Reply-To: <iuj17v$o6s$1@dough.gmane.org>
On 07/01/2011 02:35 AM, Nikos Chantziaras wrote:
> On 07/01/2011 12:45 AM, Frank Peters wrote:
>> Hello,
>>
>> After banging my head for a while over some strange results, I began
>> to suspect GCC-4.5.2, the latest version in portage, was creating
>> faulty code.
>>
>> It seems to a correct suspicion.
>> [...]
>> int n;
>> double x;
>> unsigned long int arg;
>> unsigned long int *px = (unsigned long int*)&x;
>
> Your code is buggy, because you're breaking C's aliasing rules. You are
> not allowed to use a different pointer type to dereference a variable of
> a different type. Doing so results in undefined behavior.
And here you can read more thorough information about strict aliasing:
http://labs.qt.nokia.com/2011/06/10/type-punning-and-strict-aliasing
next prev parent reply other threads:[~2011-06-30 23:45 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-30 21:45 [gentoo-amd64] GCC-4.5.2 Has Serious Problems Frank Peters
2011-06-30 22:30 ` Alex Schuster
2011-06-30 23:34 ` Frank Peters
2011-06-30 23:35 ` [gentoo-amd64] " Nikos Chantziaras
2011-06-30 23:44 ` Nikos Chantziaras [this message]
2011-07-01 0:04 ` Frank Peters
2011-07-01 0:11 ` Nikos Chantziaras
2011-07-01 0:58 ` Duncan
2011-07-01 1:23 ` Frank Peters
2011-07-01 1:52 ` Duncan
2011-07-01 2:15 ` Ian McCulloch
2011-07-01 4:36 ` Mark Knecht
2011-07-01 5:22 ` Frank Peters
2011-07-01 0:25 ` Frank Peters
2011-07-01 1:04 ` Frank Peters
2011-07-01 2:18 ` Duncan
2011-07-01 2:22 ` Barry Schwartz
2011-07-01 2:43 ` Frank Peters
2011-07-01 11:53 ` Nikos Chantziaras
2011-07-01 16:53 ` Frank Peters
-- strict thread matches above, loose matches on Subject: below --
2011-07-01 2:30 Ian McCulloch
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