On 08/02/13 18:52, Ralph Tandetzky wrote:
It wouldn't work to add the cow logic on top of a shared_ptr, when polymorphism is involved. Then an explicit clone() member function of the template type would be needed. The nice thing about the cow_ptr is that you can get this cloning facility non-intrusively.
I don't see how doing that while using shared_ptr is a problem. Either you make a shared_ptr of your structure that contains your cloning thing, or you store it separately. Of course you'll need to change the virtual function declaration to T* clone(T*), since the structure wouldn't contain the object anymore. Storing it separately seems like a better idea since it avoids the unneeded use of dynamic allocation (all derived types are the same size).