C++_练习—多态_证明vptr指针的存在

证明vptr指针的存在

 

 1 // 证明vptr指针的存在
 2 
 3 #include <iostream>
 4 
 5 using namespace std;
 6 
 7 class parent {
 8 public:
 9     parent(int a) {
10         this->a = a;
11     }
12 
13     virtual void pri(void) {
14         cout << "parent =  "<< a << endl;
15     }
16 
17 private:
18     int a;
19 };
20 
21 class child :public parent {
22 public:
23     child(int b) :parent(6) {
24         this->b = b;
25     }
26 
27     virtual void pri(void) {
28         cout << "child =  " << b << endl;
29     }
30 
31 private:
32     int b;
33 };
34 
35 int main(void)
36 {
37     parent par(1);
38     child chi(2);
39 
40     parent *p = NULL;
41 
42     //p = &par;
43       p = &chi;
44 
45       p->pri();
46 
47       cout << sizeof(par) << endl;  // 8个字节 = int + vpre 指针 （函数在代码段不占）
48       cout << sizeof(chi) << endl;  //12个字节 = int + int + vptr指针（继承父类）
49 
50     system("pause");
51 
52     return 0;
53 }

 

 

笔记

 

 

 

 

 

 

 

posted @ 2019-08-20 09:37  panda_w  阅读(231)  评论(0)    收藏  举报