this is a gcc file, you can download it and learn its usetility, for further detail please look at t

				// Build don't link:								class A {				protected:				  int aData;				};				 				class B : public A {				public:				  virtual void func1() { 				    A::aData = 1;				  }				};								class C : virtual public B {				public:				  virtual void func1(void) {				    A::aData = 2;				  }				};