Re: [boost] [smart_ptr] refactored enable_shared_from_this

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-04-26 12:10:28

Daniel Frey:
> My new version even allows one more use case:
>
> When the refactored implementation reaches line 130, the
> weak_count.use_count() == 0 is true, thus init_weak_once() initializes a
> fresh _shared_count/_weak_count pair and expects someone else to take
> over ownership later as if the object was just created.

Yes. What is the motivation for this use case?

Given the sequence:

1. Object is created
2. A shared_ptr takes ownership
3. Owner dies
4. Another shared_ptr takes ownership

the original esft allowed shared_from_this calls after 2 and 4, but not 
after 1 or 3. The new esft allows shared_from_this after 1 as well with the 
motivation to support calls from within the object constructor. But the 
constructor only runs once, so this motivation doesn't extend to 3.