Re: [boost] Re: smart_ptr suggestion: Support decrementing shared_ptr'scount,forself-references

From: Larry Evans (jcampbell3_at_[hidden])
Date: 2003-05-27 17:51:10

Chuck Messenger wrote:
[snip]
> In general, the abstraction is: you have a group of intra-referential 
> objects.  When any of the group is constructed, they are all constructed 
> (so that the master count is temporarily > 1), and the master count is 
> reset to 1.  When the master count goes to 0, the group is destructed. 
> Hence, the group only remains alive as long as there are any external 
> references (and as long as the intra-group references remain static).
> 
> Could a standard smart pointer be designed to encapsulate this 
> abstraction?  Hmmm....
Just FYI, this "abstraction" is the basic idea behind recoverying
cycles in:

   http://www.cs.kent.ac.uk/people/staff/rej/cgi-bin/searchbib?pattern=Cyclic+reference+counting+with+lazy+mark-scan.

Chrisopher's altorithm:

   http://www.cs.kent.ac.uk/people/staff/rej/cgi-bin/searchbib?pattern=Christopher+Reference+count+garbage+collection

is basically the same, except the "group" is the whole heap.  Christopher's
is the basis of Colvin's cyclic_ptr:

   http://groups.yahoo.com/group/boost/files/smart_pointers/cyclic_ptr/