1struct VBase 2{ 3 virtual void f () {} 4 VBase(); 5 ~VBase(); 6}; 7 8struct StreamBase 9{ 10 virtual ~StreamBase() {} 11}; 12 13struct Stream : public virtual VBase, public StreamBase 14{ 15 Stream(); 16 virtual ~Stream() {} 17}; 18 19struct DerivedStream : public Stream 20{ 21 DerivedStream(); 22}; 23