Peter Dimov wrote:
[...] shared_ptr<socket> is the easy part, although this immediately leads me to ask the obvious question: why isn't a socket already a shared_ptr<socket_impl>?
While Christopher can certainly answer better than i can, i think that the answer is: because it often doesn't need to be! A socket is a non copyable value based object. It doesn't need dynamic allocation and could very well be stack based (as the datagram_socket and the socket_acceptor in the example). Only if you need the lifetime of the object to be dynamic (as the example does, but it is *not* always the case) you directly allocate it. Or make it be a member of a class that is itself dynamically allocated. You could make the socket class hold internally a shared_ptr to a socket_impl and make it (shallow) copyable, but it would it be surprising and would require dynamic allocation(*) even if not needed. A nice solution would be to make socket movable... (*) Not really, all copies of stream could hold a copy of socket_imp and only the last one would close it, but it would still require some sort of reference counting. -- Giovanni P. Deretta