-----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users- bounces@lists.boost.org] On Behalf Of Steven T. Hatton Sent: Friday, December 01, 2006 7:03 AM To: Boost-users@lists.boost.org Subject: [Boost-users] boost::weak_ptr and boost::intrusive_ptr
Intrusive pointers are, IMO, the correct mechanism to hold a tree together. They are efficient, effective, and easy to understand. They work better than shared pointers for recursive data structures. Unfortunately the lack of a corresponding weak_ptr to go with boost::intrusive_ptr means I either use a raw pointer to the parent, devise a strategy for decrementing the pointers myself, or create my own weak pointer.
[Nat] I've thought about this problem to some extent. This is the way I see it so far. The one big advantage of a weak_ptr over a raw pointer is that the weak_ptr can tell you when its referent becomes invalid. If your data structure requires storing a pointer in a place which itself becomes invalid as soon as the referent becomes invalid (e.g. recursive deletion of a subtree), then I'm not convinced that weak_ptr is significantly better than a raw pointer. (Even "snipping loose" a subtree, but preserving it, doesn't seem to argue for weak_ptr as a parent pointer. In such a case, you'd want to clear the parent pointer anyway, wouldn't you?) Does this rationale make sense, or am I overlooking something? I'm not rejecting the idea of a weak_ptr that works with intrusive_ptr. I'm just saying that for certain use cases, raw pointers seem to address the requirements equally well -- with less runtime overhead. This case looks like one of them.