Re: [boost] Re: Re: Re: Mini-review request: aligned_storage.hpp

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2002-08-11 03:42:07

At Friday 2002/08/09 10:02, you wrote:
>On Friday 09 August 2002 01:31 pm, Itay Maman wrote:
> > >Obviously, you need to account for alignment, and with variant it is a bit
> >
> > more complex in the
> >
> > >implementation due to the multiple types, but the idea is the same.
> > >
> > >Also, if you want assignment to actually perform assignment on the
> >
> > underlying type, rather than
> >
> > >just transfer the value into the variant, then things are more
> > > complicated.
> > >
> > >Anthony
> >
> > Seems like a very reasonable compromise. I am certainly in favor of this
> > trick.
> > Anyway, this complicates the issue of safety vs. speed vs. sapce even
> > further.
> >
> > Eric, Doug comments?
>
>I think it's interesting to note that this trick could come "for free" if
>there is a large type that can always be swapped/assigned giving the strong
>guarantee and a smaller type that doesn't have such properties. For instance:
>
>   variant<double[5], crazy_type> v;
>
>where crazy_type is a type with strange behavior, but whose size is less than
>the size of 2 doubles.

I don't believe that a simple exchange of bits over sizeof(object) is 
sufficient in all cases to perform a swap.

>         Doug
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Victor A. Wagner Jr.      http://rudbek.com
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