Re: [boost] [Endian] Performance

Subject: Re: [boost] [Endian] Performance
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2011-09-10 07:29:44

On 09/09/2011 05:45 PM, Beman Dawes wrote:
> On Fri, Sep 9, 2011 at 8:53 AM, John Filo<filo_at_[hidden]>  wrote:
>
>> On 09/09/2011 03:29 AM, Mathias Gaunard wrote:
>>
>>> 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.
>>>
>>
>> I wondered about that; I assumed that since the return statement was the
>> only memory read from memory in the function, and that there were no writes
>> that aliasing wouldn't be a problem.  Also, I had -Wall on and GCC didn't
>> complain, so I assumed it was okay. I guess I need to read up on what the
>> exact rules are.
>>
>
> I'm missing something. Could you please post the full function, without any
> preprocessing statements, where the aliasing issue is arising?

It's arising in the snippet above...