Re: [boost] Re: basic guarantees in variant

From: Brian McNamara (lorgon_at_[hidden])
Date: 2003-10-08 23:17:35

On Wed, Oct 08, 2003 at 08:48:28PM -0700, E. Gladyshev wrote:
> Here is how I would do it.
...
> //doesn't throw
> void variant_copy( char* dst, char* src, size_t size ) {
>     for( size_t i = 0; i < size; ++i, ++dst, ++src ) {
>         *dst =  *src;
>     }
> }
...
>         //save the current data
>         variant_copy( b1, data_, size );
...
>             //copy the new object to another storage
>             variant_copy( b2, data_, size );
>             //copy the original object back for destruction
>             variant_copy( data_, b1, size );
>             static_cast<T*>((void*)data_)->~T();
>             //put the new object back in place
>             variant_copy( data_, b2, size );

This is clever.  Is it legal?  I know it's legal for POD types.  I can't
find text in the standard which makes it legal for non-POD types.  But
at the same time, offhand I can't imagine an implementation where it
wouldn't work.

Can you treat a non-POD type as a "bag of bits" temporarily, just to
move it off to the side, and then move it back to the same location and
treat it as an object again?

-- 
-Brian McNamara (lorgon_at_[hidden])