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Subject: Re: [boost] [Endian] Performance
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2011-09-09 04:29:46

On 07/09/2011 14:16, John Filo wrote:

> I.e. I added:
> #elif USE_BIG
> return *reinterpret_cast<const ubig32_t*>(&src);
> #elif USE_LITTLE
> return *reinterpret_cast<const ulittle32_t*>(&src);
> #elif USE_NATIVE
> return src;

This breaks aliasing rules.

> and on a Intel Core2 with gcc-4.4.3, I get the following results at
> -O2 (except where noted, -O3 and -O4 produced nearly identical
> results):

GCC is one of the few compilers that follow aliasing rules.
There is no guarantee that the code generated is correct.

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