Re: [Boost-users] shared_ptr invalid covariant return type

John skrev:

This pattern/idiom is well-established:

struct A { virtual A* clone () = 0; };

struct B : public A { virtual B* clone (); };

But the above does not work when the pointers A* and B* are replaced by shared_ptr<A> and shared_ptr<B>:

struct A { virtual shared_ptr<A> clone () = 0; };

struct B : public A { virtual shared_ptr<B> clone (); };

Is there a workaround? Another way to solve the same problem? Thanks!

Well, don't use shared_ptr here. A newly created clone is not shared, and it makes the interface less usable in other context to return a shared ptr here. -Thorsten