Re: [boost] [shared_ptr] dangerous implementation of moveconstructor

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2007-04-17 01:07:58

Peter Dimov wrote:
> To get back to shared_ptr, given p and q of type shared_ptr, would you be 
> extremely disappointed if after:
> 
>     p = move( q );
> 
> q holds the old value of p instead of being empty?
> 
> (Note that p may have had a value that you could consider "unsafe" in the 
> context of the valid values of q.) 

Thinking it twice. Wouldn't simple swap lead to the false impression 
that the reference count for the object p was pointing was dropped? If p 
was the last reference to that value, wouldn't the user be surprised if 
value is not destroyed (with its side effects) just when p is 
move-assigned? If the user does not destroy q, the value is staying 
there. OTOH, this could make move-assignment more expensive because it 
might destroy objects.

Just a thought,

Ion