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c.f. bug 424647
List Archive: gentoo-amd64
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To: gentoo-amd64@g.o
From: Nikos Chantziaras <realnc@...>
Subject: Re: GCC-4.5.2 Has Serious Problems
Date: Fri, 01 Jul 2011 02:44:36 +0300
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



Replies:
Re: Re: GCC-4.5.2 Has Serious Problems
-- Frank Peters
Re: Re: GCC-4.5.2 Has Serious Problems
-- Frank Peters
Re: Re: GCC-4.5.2 Has Serious Problems
-- Frank Peters
References:
GCC-4.5.2 Has Serious Problems
-- Frank Peters
Re: GCC-4.5.2 Has Serious Problems
-- Nikos Chantziaras
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Updated Jun 04, 2012

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