学步园

#include <iostream>

using namespace std;

class Base {
public:
    Base() {
        cout << "In Base" << endl;
        cout << "Virtual Pointer = " << (int*)this << endl;
        cout << "Address of Vtable = " << (int*)*(int*)this << endl;
        cout << "Value at Vtable 1st entry = " << (int*)*((int*)*(int*)this+0) << endl;
        cout << "Value at Vtable 2nd entry = " << (int*)*((int*)*(int*)this+1) << endl;
        cout << "Value at Vtable 3rd entry = " << (int*)*((int*)*(int*)this+2) << endl;
cout << endl;
    }
    virtual void f1() { cout << "Base::f1" << endl; }
    virtual void f2() { cout << "Base::f2" << endl; }
};

class Drive : public Base {
public:
    Drive() {
        cout << "In Drive" << endl;
        cout << "Virtual Pointer = " << (int*)this << endl;
        cout << "Address of Vtable = " << (int*)*(int*)this << endl;
        cout << "Value at Vtable 1st entry = " << (int*)*((int*)*(int*)this+0) << endl;
        cout << "Value at Vtable 2nd entry = " << (int*)*((int*)*(int*)this+1) << endl;
        cout << "Value at Vtable 3rd entry = " << (int*)*((int*)*(int*)this+2) << endl;
        cout << endl;
    }
    virtual void f1() { cout << "Drive::f1" << endl; }
};

int main() {
    Drive d;
    return 0;
}

运行结果

In Base
Virtual Pointer = 0012FF7C
Address of Vtable = 0046C0E0
Value at Vtable 1st entry = 004010F0
Value at Vtable 2nd entry = 00401145
Value at Vtable 3rd entry = 00000000

In Drive
Virtual Pointer = 0012FF7C
Address of Vtable = 0046C0C8
Value at Vtable 1st entry = 0040121C
Value at Vtable 2nd entry = 00401145
Value at Vtable 3rd entry = 00000000