Re: [boost] aligned_storage in unions

Subject: Re: [boost] aligned_storage in unions
From: Trigve Siver (trigves_at_[hidden])
Date: 2010-09-24 04:52:22

> From: David Abrahams <dave_at_[hidden]>

> To: "boost_at_[hidden]" <boost_at_[hidden]>
> Sent: Thu, September 23, 2010 7:18:22 PM
> Subject: Re: [boost] aligned_storage in unions
> 
> 
> On Sep 23, 2010, at 11:37 AM, Frank Mori Hess wrote:
> > 
> >  What is this based on?  There is a strict aliasing exception for char*, but 

> > all I see in the standard about static_casting through void is  (paragraph 10 
>
> > of 5.2.9):
> 
> Sorry, no time to trawl the standard  right now.  The above matches my hard-won 
>understanding but of course I  could always be wrong about anything ;-)

I think u mean 9.2/19:

"A pointer to a standard-layout struct object, suitably converted using a 
reinterpret_cast, points to its initial member (or if that member is 

a bit-field, then to the unit in which it resides) and vice versa. [ Note: There 
might therefore be unnamed padding within a standard-layout 

struct object, but not at its beginning, as necessary to achieve appropriate 
alignment. =97end note ]" 

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