Re: [boost] [optional] problems with swap()

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-04-11 16:43:00

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On Friday 11 April 2008 15:00 pm, Fernando Cacciola wrote:
> Hi Thorsten,
>
> Adding the new requirement is out of the question, but it's definitely
> possible to choose default construction or zero-initialization as
> appropiate. And IMO that magic would be best placed within
> boost::in_place() itself since it makes a lot of sense, given its nature,
> to do
> zero-initialization for non-default constructible types.
>
> With such a smart in_place factory, the optional swap implementation would
> look exactly as you proposed it AFAICT.

If I'm following, you're proposing calling swap on an object which doesn't 
really exist, but is just a zero'ed block of memory?  Wouldn't that be 
undefined behavior?  Suppose the template type contains a mutex and its swap 
specialization tries to lock the mutexes for both objects before swapping 
their contents.  It would crash wouldn't it?

- -- 
Frank
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