"Peter Petrov" <ppetrov@ppetrov.com> wrote in message news:loom.20041118T102318-791@post.gmane.org...
Gennadiy Rozental <gennadiy.rozental <at> thomson.com> writes:
Here we do very simple (or complex,depends on point of view) trick instead of above Let say we have somewhere map<T*,shared_ptr<T>*> registry;
if( registry[raw_ptr] == 0 ) { t = shared_ptr<T>( raw_ptr ) registry.add( raw_ptr, &t ); } else t = *registry[raw_ptr];
// current shared_ptr implementation depends upon an internal pointer
to
a shared count. }
Do I miss something important?
What happens when some time after deserialization, one of the deserialized shared_ptr's is destroyed? Your "registry" has no way to know that and will still hold a shared_ptr referencing the same object, which is not correct.
Maybe we can do this instead: map<T*,weak_ptr<T> > registry; weak_ptr<T> ®istered = registry[raw_ptr]; t = registered.lock(); if (!t) { t = shared_ptr<T>(raw_ptr); registered = t; } After all, one of the main uses for weak_ptr is to implement a cache of shared_ptr's. Joe Gottman