多态-虚函数表

VS的对象内存分析:

/d reportSingleClassLayout+类名

 使用方法:项目 -- 属性 -- C/C++ -- 命令行--其他选型(D) 添加命令.如图所示:

Father类:

class Father {
public:virtual void Func1() { cout << "Father::Func1" << endl; }virtual void Func2() { cout << "Father::Func2" << endl; }virtual void Func3() { cout << "Father::Func3" << endl; }void Func4() { cout << "Father::Func4" << endl; }
public:int x = 200;int y = 300;static int z;
};
int Father::z = 0;

Father的内存分析: 

/d reportSingleClassLayoutFather

Son类: public Father

class Son:public Father
{
public:void Func1() { cout << "Son::Func1" << endl; }virtual void Func5() { cout << "Son::Func5" << endl; }private:int m = 400;int n = 500;
};

Son类的内存分析: 

/d reportSingleClassLayoutSon

 子类的虚函数表构建过程:

(1)直接复制父类的虚函数表

(2)如果子类重写了父类的某个虚函数,那么就在这个虚函数表中进行相应的替换

(3)如果子类中添加了新的虚函数,就把这个虚函数添加到虚函数的表中(在尾部添加)

 注意:所有子类共用同一张虚函数表

main函数:

int main(void) {Son son;Father* father = &son;cout << "----Father* father = &son----" << endl;son.Func1();son.Func2();son.Func3();son.Func4();son.Func5();Father* son2 = new Son();cout << "----Father* son2 = new Son()----" << endl;son2->Func1();son2->Func2();son2->Func3();son2->Func4();//son2->Func5();//错误使用return 0;
}

结果:

 全部代码(测试):

#include<iostream>
using namespace std;
//vs的对象内存分析：/d1 reportSingleClassLayout+类名
class Father {
public:virtual void Func1() { cout << "Father::Func1" << endl; }virtual void Func2() { cout << "Father::Func2" << endl; }virtual void Func3() { cout << "Father::Func3" << endl; }void Func4() { cout << "Father::Func4" << endl; }
public:int x = 200;int y = 300;static int z;
};
int Father::z = 0;class Son:public Father
{
public:void Func1() { cout << "Son::Func1" << endl; }virtual void Func5() { cout << "Son::Func5" << endl; }private:int m = 400;int n = 500;
};typedef void(*func)(void);void test(void) {Father father;cout << "sizeof(father): " << sizeof(father) << endl;cout << "(int*)&father: " << (int*)&father << endl;cout << "&father: " << &father << endl;int* vptr = (int*)*(int*)(&father);cout << "调用虚函数Func1:" << endl;((func) * (vptr + 0))();cout << "调用虚函数Func2:" << endl;((func) * (vptr + 1))();cout << "调用虚函数Func3:" << endl;((func) * (vptr + 2))();cout << "father.x地址: " << endl;cout << &father.x << endl;cout << (int*)((int)&father + 4) << endl;cout << "father.x:" << endl;cout << father.x << endl;cout << *(int*)((int)&father + 4) << endl;cout << "father.y地址: " << endl;cout << &father.y << endl;cout << (int*)((int)&father + 8) << endl;cout << "father.y:" << endl;cout << father.y << endl;cout << *(int*)((int)&father + 8) << endl;
}int main(void) {test();Son son;Father* father = &son;cout << "----Father* father = &son----" << endl;son.Func1();son.Func2();son.Func3();son.Func4();son.Func5();Father* son2 = new Son();cout << "----Father* son2 = new Son()----" << endl;son2->Func1();son2->Func2();son2->Func3();son2->Func4();//son2->Func5();//错误使用return 0;
}