[gentoo-amd64] Re: GCC-4.5.2 Has Serious Problems

[Nikos Chantziaras]

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