[C++知识库]C++ 虚表测试程序

测试C++虚表

#include <iostream>

using namespace std;

class base {
    public:
        virtual void f() { cout << "base::f" << endl; }
        virtual void g() { cout << "base::g" << endl; }
        virtual void h() { cout << "base::h" << endl; }
    long a = 1;
};

class Derive : public base {
public:
	void f() override {cout << "deriver::f" << endl; }
    virtual void i() { cout << "derive::i" << endl; }
    virtual void j() { cout << "derive::j" << endl; }
};

typedef void(*Fun)(void);
int main()
{
    base b;
    Derive d;
    Fun pFun = nullptr;

    cout << "the address of vtable:" << (long *)(&b) << endl;
    cout << "the address of first func:" << (long*)*(long*)(&b) << endl;
    cout << "the member of base " << *((long *)(&b) + 1) << endl;

    pFun = (Fun)*((long*)*(long*)(&b));
    pFun();

    pFun = (Fun)*((long*)*(long*)(&b) + 1);
    pFun();

    pFun = (Fun)*((long*)*(long*)(&b) + 2);
    pFun();

    d.a = 1;
    cout << "the address of vtable:" << (long *)(&d) << endl;
    cout << "the address of first func:" << (long*)*(long*)(&d) << endl;
    cout << "the member of derive " << *((long*)*(long*)(&d) + 5) << endl;
    pFun = (Fun)*((long*)*(long*)(&d));
    pFun();

    pFun = (Fun)*((long*)*(long*)(&d) + 1);
    pFun();

    pFun = (Fun)*((long*)*(long*)(&d) + 2);
    pFun();

    pFun = (Fun)*((long*)*(long*)(&d) + 3);
    pFun();

    pFun = (Fun)*((long*)*(long*)(&d) + 4);
    pFun();

    return 0;
}

运行结果

the address of vtable:0x7fff0ae91750
the address of first func:0x558919f83d30
the member of base 1
base::f
base::g
base::h
the address of vtable:0x7fff0ae91760
the address of first func:0x558919f83cf8
the member of derive 0
deriver::f
base::g
base::h
derive::i
derive::j