[C++] 虚指针，虚表，虚函数地址打印

#include <iostream>
using namespace std;

class Base
{
public :
int base_data;
Base() { base_data = 1; }
virtual void func1() { cout << "base_func1" << endl; }
virtual void func2() { cout << "base_func2" << endl; }
virtual void func3() { cout << "base_func3" << endl; }
};

class Derive : public Base
{
public :
int derive_data;
Derive() { derive_data = 2; }
virtual void func1() { cout << "derive_func1" << endl; }
virtual void func2() { cout << "derive_func2" << endl; }
};

typedef void (*func)();

int main()
{
Base base;
cout << "&base: " << &base << endl;
cout << "&base.base_data: " << &base.base_data << endl;
cout << "----------------------------------------" << endl;

Derive derive;
cout << "&derive: " << &derive << endl;
cout << "&derive.base_data: " << &derive.base_data << endl;
cout << "&derive.derive_data: " << &derive.derive_data << endl;
cout << "----------------------------------------" << endl;

for(int i=0; i<3; i++)
{
// &base : base首地址
// (unsigned long*)&base : base的首地址，vptr的地址
// (*(unsigned long*)&base) : vptr的内容，即vtable的地址，指向第一个虚函数的slot的地址
// (unsigned long*)(*(unsigned long*)&base) : vtable的地址，指向第一个虚函数的slot的地址
// vtbl : 指向虚函数slot的地址
// *vtbl : 虚函数的地址
unsigned long* vtbl = (unsigned long*)(*(unsigned long*)&base) + i;
cout << "slot address: " << vtbl << endl;
cout << "func address: " << *vtbl << endl;
func pfunc = (func)*(vtbl);
pfunc();
}
cout << "----------------------------------------" << endl;

for(i=0; i<3; i++)
{
unsigned long* vtbl = (unsigned long*)(*(unsigned long*)&derive) + i;
cout << "slot address: " << vtbl << endl;
cout << "func address: " << *vtbl << endl;
func pfunc = (func)*(vtbl);
pfunc();
}
cout << "----------------------------------------" << endl;
return 1;
}