Re: [boost] [optional] Strict Aliasing Warnings on Trunk

Subject: Re: [boost] [optional] Strict Aliasing Warnings on Trunk
From: Giovanni Piero Deretta (gpderetta_at_[hidden])
Date: 2009-12-19 15:55:37

On Fri, Dec 18, 2009 at 9:19 PM, Emil Dotchevski
<emildotchevski_at_[hidden]> wrote:
> On Fri, Dec 18, 2009 at 11:07 AM, Felipe Magno de Almeida
> <felipe.m.almeida_at_[hidden]> wrote:
>> On Fri, Dec 18, 2009 at 4:57 PM, Emil Dotchevski
>> <emildotchevski_at_[hidden]> wrote:
>>> On Fri, Dec 18, 2009 at 5:46 AM, Felipe Magno de Almeida
>>> <felipe.m.almeida_at_[hidden]> wrote:
>>
>> [snip]
>>
>>>> But nothing else is guaranteed. The compiler might very well increment
>>>> it by one byte when casting to T2 and then decrement it when casting
>>>> it back. It is perfectly valid behavior for reinterpret_cast.
>>>
>>> It is perfectly portable as well.
>>
>> It is not portable if we dereference it, which optional does.
>
> I am going off of what Giovanni said earlier in this thread about how
> optional works, which seems to contradict your statement above.
>

Just to clarify, my comment was only about aliasing issues, i.e. in my
opinion boost.optional has none.

I didn't comment on boost.optional usage of reinterpret_cast. That's a
completely orthogonal issue (FWIW, I think that static_cast is
theoretically better, but in practice I do not think that it would
make any difference with any existing compiler)

-- 
gpd