C++_练习—多态_证明vptr指针的存在

证明vptr指针的存在

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// 证明vptr指针的存在

#include <iostream>

using namespace std;

class parent {
public:
    parent(int a) {
        this->a = a;
    }

    virtual void pri(void) {
        cout << "parent =  "<< a << endl;
    }

private:
    int a;
};

class child :public parent {
public:
    child(int b) :parent(6) {
        this->b = b;
    }

    virtual void pri(void) {
        cout << "child =  " << b << endl;
    }

private:
    int b;
};

int main(void)
{
    parent par(1);
    child chi(2);

    parent *p = NULL;

    //p = &par;
      p = &chi;

      p->pri();

      cout << sizeof(par) << endl;  // 8个字节 = int + vpre 指针 （函数在代码段不占）
      cout << sizeof(chi) << endl;  //12个字节 = int + int + vptr指针（继承父类）

    system("pause");

    return 0;
}

 

 

笔记

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