Re: [boost] [smart_ptr] trunk versionof enable_shared_from_thisincompatible with TR1

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-05-03 13:52:18

Frank Mori Hess:

> What I'm thinking is more along the lines of how a weak_ptr goes from 
> "expired" to "good".  Currently, that can only happen by assignment of a 
> new shared_ptr.  And assignment of one expired weak_ptr has no effect on 
> any copies of the weak_ptr, they stay expired.

This is correct as far as it goes. But in the case I showed, no assignment 
happens to any of the weak_ptr instances. Consider how weak_ptrs go from 
use_count of 1 to use_count of 0 without any assignment. This is the same 
event in reverse. It can't normally occur now, of course.

Remember that use_count() does not report the state of a particular 
instance, it reports program-wide state (the number of shared_ptr instances 
sharing ownership with *this). It can and will go up and down without any 
changes to *this.

> Yes, but in the case of a long-lived signal with many short-lived 
> connections, it would effectively create a resource leak when relying on 
> automatic connection management.

Well, there would be no automatic connection management, so obviously 
relying on it would be a bad idea. :-) One would have to use scoped 
connections or manual disconnects in the destructor, as usual.