108.虚函数表原理(获取虚函数)

 1 //#include <iostream>
 2 //using namespace std;
 3 //
 4 //
 5 //void main()
 6 //{
 7 //    cin.get();
 8 //}
 9 
10 #define _CRT_SECURE_NO_WARNINGS
11 #include <iostream>
12 using namespace std;
13 
14 class father
15 {
16 public:
17     //虚函数表存放在首地址
18     virtual void go1()
19     {
20         cout << "go1" << endl;
21     }
22     virtual void go2()
23     {
24         cout << "go2" << endl;
25     }
26     virtual void go3()
27     {
28         cout << "go3" << endl;
29     }
30 };
31 
32 class son :public father
33 {
34 public:
35 
36     void go1()
37     {
38         cout << "son go1" << endl;
39     }
40 
41     void go2()
42     {
43         cout << "son go2" << endl;
44     }
45 
46     void go3()
47     {
48         cout << "son go3" << endl;
49     }
50 };
51 
52 void main()
53 {
54     father *p = new son;
55     cout << sizeof(*p) << endl;
56     //对象的地址
57     cout << (void*)p << endl;
58     //虚函数表的地址
59     cout << (void*)(*((int *)p)) << endl;
60     //第一个元素的地址 类型转换->读内存->类型转换使得步长为4个字节
61     cout << (void*)(   ((int *)*((int *)p) +0)      ) << endl;
62     
63     //取出函数表中的函数
64 
65     auto fun1 = (void*)(   *((int *)*((int *)p) + 0)   );
66     auto fun2 = (void*)(   *((int *)*((int *)p) + 1)   );
67     auto fun3 = (void*)(   *((int *)*((int *)p) + 2)   );
68 
69     typedef void(*P)();
70 
71     //函数指针数组
72     P pfun[3];
73     pfun[0] = (P)fun1;
74     pfun[1] = (P)fun2;
75     pfun[2] = (P)fun3;
76 
77     for (int i = 0; i < 3; i++)
78     {
79         pfun[i]();
80     }
81     cin.get();
82 }