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

[Nikos Chantziaras]

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.

Short answer, GCC is correct, you are wrong :-)  To compile code that 
breaks aliasing rules, always use the "-fno-strict-aliasing" option.  In 
this case:

   gcc -O2 -fno-strict-aliasing