C++虚函数的陷阱

 1 class B   
 2 {    
 3 public:   
 4     virtual void fun(int i = 1)      
 5     {     
 6         std::cout << "base fun called, " << i;     
 7     };    
 8 };  
 9 
10 class D : public B    
11 {    
12 private:    
13     virtual void fun(int i = 2)      
14     {     
15         std::cout << "driver fun called, " << i;     
16     };    
17 };