C++虚函数

#include <iostream>

using namespace std;

class Base1 {
public:
	Base1(){}
	void display();
};

class Base2:public Base1 {
public:
	Base2(){}
	void display();
};

class Derive:public Base2 {
public:
	Derive(){}
	void display();
};

void Base1::display()
{
	cout<<"Base1::fun()"<<endl;
}

void Base2::display()
{
	cout<<"Base2::fun()"<<endl;
}



void Derive::display()
{
	cout<<"Derive::fun()"<<endl;
}


void fun(Base1 *p)
{
	p->display();
}

int main()
{
	Base1 b1;
	Base2 b2;
	Derive d;
	
	fun(&b1);
	fun(&b2);
	fun(&d);

}

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</span>

$ g++ -o test2 test2.cpp
$ ./test2
Base1::fun()
Base1::fun()
Base1::fun()

#include <iostream>

using namespace std;

class Base1 {
public:
	Base1(){}
	virtual void display();
};

class Base2:public Base1 {
public:
	Base2(){}
	void display();
};

class Derive:public Base2 {
public:
	Derive(){}
	void display();
};

void Base1::display()
{
	cout<<"Base1::fun()"<<endl;
}

void Base2::display()
{
	cout<<"Base2::fun()"<<endl;
}



void Derive::display()
{
	cout<<"Derive::fun()"<<endl;
}


void fun(Base1 *p)
{
	p->display();
}

int main()
{
	Base1 b1;
	Base2 b2;
	Derive d;
	
	fun(&b1);
	fun(&b2);
	fun(&d);

}

$ g++ -o test3 test3.cpp
$ ./test3
Base1::fun()
Base2::fun()
Derive::fun()