[boost] Re: new approach to smart ptrs -- no new()s is good news

From: Gavin Collings (gcollings_at_[hidden])
Date: 2000-01-28 12:16:58

> I think I discovered a new approach for smart pointers (tell me if
> this has been done).  Instead of maintaining the reference count as
> an integer created on the heap, the smart ptr objects internally
> maintain a double-linked list in which they are members.
> 

I have this implemented as a template with minor differences: -

-  I set the "unique" pointer values to point to self to avoid null
tests
  
-  I think there's a bug in your swap function - you need to adjust the
back pointer in other objects to reflect that this now collaborates
with a different set of smart pointers.

-  I have the list pointers as mutable to reflect the fact that they may
be changed by other objects.

I've done timing tests which agree with yours,  I also tried to
characterize the speed advantage against set size and found that
there's a cross over at about 25-50 members -i.e. the current
implementation becomes more efficient when greater than that number
share a single pointer.

There is also an additional benefit of better exception guarantees. 
I'm all for it.

Gavin