Re: [boost] [Smart Ptr] make_shared slower than shared_ptr(new) on VC++9 (and 10) with fix

Subject: Re: [boost] [Smart Ptr] make_shared slower than shared_ptr(new) on VC++9 (and 10) with fix
From: Dave Abrahams (dave_at_[hidden])
Date: 2012-04-26 16:32:08

on Thu Apr 26 2012, Mathias Gaunard <mathias.gaunard-AT-ens-lyon.org> wrote:

> On 26/04/12 19:41, Dave Abrahams wrote:
>>
>> on Thu Apr 26 2012, "Stephan T. Lavavej"<stl-AT-exchange.microsoft.com>  wrote:
>>
>>> [STL]
>>>> Each is optimally sized (in particular, make_shared/allocate_shared
>
>>>> implement the "we know where you live" optimization that I have
>>>> previously described
>>>
>>> [Dave Abrahams]
>>>> I can't find that description.  Pointer please?
>>>
>>> See
>>> http://channel9.msdn.com/Events/GoingNative/GoingNative-2012/STL11-Magic-Secrets
>>> (which also has links to my slides - viewable online even without
>>> PowerPoint), in particular Slide 6.
>>
>> 9:30 or so in the video.
>
> Explicit destructor calls on memory that doesn't come from the free store?
> Sounds like there are potential strict aliasing problems there.

I think, based on what you said here and your comments in the newsgroup,
that you are misreading those rules.  You're allowed to construct
anything you want in a raw array of char as long as it's properly
aligned.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com