RE: [boost] Re: unions

From: Brock Peabody (brock.peabody_at_[hidden])
Date: 2003-10-08 18:52:57

> From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]]
> On Behalf Of E. Gladyshev

[...]

> Good summary.  I would prefer the second option.
> I think it should be possible to implement basic
> guarantees without the backup heap.
> The requirement says that variant should
> contain *a* value, so why do we need
> a backup heap.  If we don't need a backup heap
> we don't have an issues with the first-type switch.

I may be wrong, but I think they had already determined that there was no
way to get the basic guarantee for classes without no-throw copy
constructors unless they used the backup heap.  I bet they would be thrilled
if you could prove them wrong :) 

> > My personal preference would be for (3).  I'd take the performance
> penalty
> > (the double allocation?) to get the strong guarantee - just do the right
> > thing you know.
> 
> I agree with you in general, but IMO variant is a very basic type
> that should be useable in application where performance is important.

Yeah, you (and Dave) are certainly right about this.  I was just wondering
if some day it might be common to specify exception guarantee level via
policy.  I personally can't think of any places where I would care enough to
change the default, but it seemed like an interesting idea.

Brock