From: "David Abrahams" <[EMAIL PROTECTED]> > "Peter Dimov" <[EMAIL PROTECTED]> writes: > > > It's true that, in general, there is no safe way to break the cycle; x1 may > > keep a raw pointer to x2, or it might be a X invariant that X::p is > > non-empty, causing ~X to fail. This is why the final decision to break the > > cycles should be left to the user, and the collector should not > > automatically reclaim memory. Still, most reasonable classes would be > > collect-friendly. > > Isn't the biggest problem one of system design? How does the user > write the cycle-breaking code which does different things based on the > dynamic type of the objects being referenced?
The user doesn't need to write any cycle-breaking code. All that is needed is to reset() the shared_ptr instances that keep the cycle alive. I.e. the requirement is that the object's invariants must not be broken if a shared_ptr member is suddenly reset. It's not necessary to know the T in shared_ptr<T> in order to reset it if shared_ptrs are layout-compatible (true on most implementations.) _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
