【C++】多态（下）

1. 虚函数和虚表位置

• 虚函数与普通函数一样，都是存在代码段，同时虚函数地址存了一份到虚函数表
• 虚函数表存在代码段（常量区）

2. 单继承中的虚函数表

class Base { 
public :
 virtual void func1() { cout<<"Base::func1" <<endl;}
 virtual void func2() {cout<<"Base::func2" <<endl;}
private :
 int a;
};


class Derive :public Base { 
public :
 virtual void func1() {cout<<"Derive::func1" <<endl;}
 virtual void func3() {cout<<"Derive::func3" <<endl;}
 virtual void func4() {cout<<"Derive::func4" <<endl;}
private :
 int b;
};

Derive:

3. 多继承中的虚函数表

class Base1 {
public:
 virtual void func1() {cout << "Base1::func1" << endl;}
 virtual void func2() {cout << "Base1::func2" << endl;}
private:
 int b1;
};


class Base2 {
public:
 virtual void func1() {cout << "Base2::func1" << endl;}
 virtual void func2() {cout << "Base2::func2" << endl;}
private:
 int b2;
};


class Derive : public Base1, public Base2 {
public:
 virtual void func1() {cout << "Derive::func1" << endl;}
 virtual void func3() {cout << "Derive::func3" << endl;}
private:
 int d1;
};

Derive:

• 子类有几个父类，就有几张虚函数表，子类自己的虚函数地址放在第一张虚函数表内

4. 问答题