C++ 虚函数表与多态 —— 多重继承的虚函数表 & 内存布局

 1 #include <iostream>
 2 using namespace std;
 3 
 4 class Father
 5 {
 6 public:
 7     virtual void func_1() { cout << "Father::func_1" << endl; }
 8     virtual void func_2() { cout << "Father::func_2" << endl; }
 9     virtual void func_3() { cout << "Father::func_3" << endl; }
10 public:
11     int x = 666;
12     int y = 999;
13 };
14 
15 class Mother
16 {
17 public:
18     virtual void handle_1() { cout << "Mother::handle_1" << endl; }
19     virtual void handle_2() { cout << "Mother::handle_2" << endl; }
20     virtual void handle_3() { cout << "Mother::handle_3" << endl; }
21 public:
22     int a = 555;
23     int b = 888;
24 };
25 
26 class Son : public Father, public Mother                    //继承了两个父类
27 {
28 public:
29     void func_1() { cout << "Son::func_1" << endl; }                //重写了 Father 虚函数
30     virtual void func_4() { cout << "Son::func_4" << endl; }        //子类对象新写的虚函数 func_4
31     void handle_1() { cout << "Son::handle_1" << endl; }            //重写了 Mother 虚函数
32 };
33 
34 typedef void(*func_t)(void);
35 
36 int main(void)
37 {
38     Son son;
39     int* vptr_s_1 = (int*)*(int*)&son;                                        //son的第一个虚表指针
40 
41     for (int i = 0; i < 4; i++)
42     {
43         cout << "调用第" << i + 1 << "个虚函数：";
44         ((func_t) * (vptr_s_1 + i))();
45     }
46 
47     for (int i = 0; i < 2; i++)
48     {
49         cout << "继承自 Father 数据成员：" << *(int*)((int)&son + 4 + i * 4) << endl;
50     }
51 
52     int* vptr_s_2 = (int*)*((int*)&son + 3);                                //son的第二个虚表指针
53     for (int i = 0; i < 3; i++)
54     {
55         cout << "调用第" << i + 1 << "个虚函数：";
56         ((func_t) * (vptr_s_2 + i))();
57     }
58 
59     for (int i = 0; i < 2; i++)
60     {
61         cout << "继承自 Mather 数据成员：" << *(int*)((int)&son + 16 + i * 4) << endl;
62     }
63 }