C语言实现C++中的虚函数机制

virtual_function

// use c to simulate the mechanism of virtual function in c++.
// designed by [email protected]

#include <iostream>

using std::cout;
using std::endl;

// C: function pointer
void fun1() {
    cout << "C fun1" << endl;
}
int fun2(int in) {
	cout << "C fun2" << endl;
	return 0;
}
void (*(v_table[2]))()  = {fun1, (void (*)())fun2};

struct A{
public:
	void (*(*v_table))();
};

// C++: virtual function
class B{
public:
	virtual void fun1() {
		cout << "C++ fun1" << endl;
	};
	virtual int fun2(int in) {
		cout << "C++ fun2" << endl;
		return 0;
	};
};

int main() {
	A a;
	a.v_table = v_table;
	(*(*a.v_table))();
	(*(int (*)(int))(*(a.v_table+1)))(0);

	B b;
	b.fun1();
	b.fun2(0);

	// in vs, you could break here, and watch the memory content of a and b.
	return 0;
}