On Thu, 2008-04-10 at 09:27 -0400, Frank Mori Hess wrote:
On Thursday 10 April 2008 06:40 am, Daniel Frey wrote:
On Wed, 2008-04-09 at 20:13 -0400, Frank Mori Hess wrote: I attached a minimalistic patch against the trunk which enhances the current code into that direction.
The static_cast in your patch is going to have problems with virtual base classes. I think you could just use the Y* available in sp_enable_shared_from_this and call _internal_accept_owner from that.
Note that 5.2.9/8 only refers to B and D's relationship. Since we are creating a new base class, we can define that non-virtual derivation is a precondition. In the patch I've shown the static_cast should be perfectly legal and it should work in all cases, AFAICT.
Also, on further thought, I don't think enable_shared_from_this_base needs to be a template class at all.
If you have an easier implementation without further overhead, I'd be happy to see it.
The name (enable_shared_from_this_base) is probably not a good name. I think that from shared_ptr's point of view, it doesn't need to know what the callback is used for. It might be better to call it notify_on_ownership or something in that direction. And the callback function should probably also be renamed. Suggestions?
I agree. notify_on_ownership seems ok. Some other possibilities are ownership_observer or shared_ptr_observer. The callback might be accept_shared_ptr_owner() or update_shared_ptr_owner()
Those are excellent suggestions. I think shared_ptr_observer and update_shared_ptr_owner are the names I like most.
Also, I don't think enable_shared_from_this should actually use this base class in the end, whatever it is called (although it is a good test). If it does, the user will have to take special care to avoid problems when deriving from both enable_shared_from_this and this base class. This might happen if the user is deriving from the base class for purposes other than re-implementing enable_shared_from_this.
Good point. I'll need some time to think about this case. Regards, Daniel