[boost] Re: Cyclic smart pointers (holy grail: the uber-point er)

From: Chuck Messenger (chuckm_at_[hidden])
Date: 2003-05-29 23:09:44

Schoenborn, Oliver wrote:

>>>>>- You always have A owns A_impl owns B owns B_impl refs A (what your
>>>>>original code seems to say), in this case B_impl contains an RRef<A> 
>>>>>instead of a DynObj<A> and everything works
>>>
>>>I'd like to hear whether that's your case or not. 
>>
>>No.  A and B are completely symmetrical.  They each equally 
>>"own" the other.
> 
> 
> Not possible. This has nothing to do with NoPtr or boost::shared_ptr, it's
> even true for raw pointers. E.g.
> ...

Just look at my Node example -- you'll see that there is indeed complete 
symmetry of ownership.  There is a cyclic ownership graph -- hence the 
trouble with traditional smart pointers.

>>However, I don't understand what NoPtr *does*.
> 
> 
> Simplistically, 
> - DynObj destroys what it owns when it goes out of scope, is reset or
> acquires something new, and notifies any RRefs linked to it
> - RRef refers to a DynObj, but asserts that DynObj still exists when
> accessed
> 
> Note that I said simplistically.

OK, thanks for the explanation -- I think I understand.

     - Chuck Messenger