Ion Gaztañaga wrote:
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.
This is the essence of the discussion. :-) I think that efficiency is more important in a move primitive than leaving the source in a predictable state, Joe argues the other way.