??????????????????
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 };
??????????????2?????
????B* p = new D();
????p->fun();
????????? driver fun called?? 1
?????????????????????
??????1?????????????????????????к???????????????????
??????2???麯??????????????????????????????????
?????????????????????