class A{public:void print(){cout << " class A " << endl;}
};class B : public A{public:void print(){cout << " class B " << endl;}
};
// gnu对象模型
int main(){cout << "The size of A is " << sizeof(A) << endl;cout << "The size of B is " << sizeof(B) << endl;B b;A &a = b;  // 利用A类的引用指向B类的对象A *c = &b; // 利用A类的指针指向B类的对象b.print();a.print();  // A类的引用调用print()c->print(); // A类的指针调用 print()// 普通函数跟着类// 虚函数跟着对象return 0;
}

class A{public:virtual void print(){cout << " class A " << endl;}
};class B : public A{public:void print() override{     // override 可不写，此处是为了编码规范cout << " class B " << endl;}
};
// gnu对象模型
int main(){cout << "The size of A is " << sizeof(A) << endl;cout << "The size of B is " << sizeof(B) << endl;B b;A &a = b;  // 利用A类的引用指向B类的对象A *c = &b; // 利用A类的指针指向B类的对象b.print();a.print();  // A类的引用调用print()c->print(); // A类的指针调用 print()return 0;
}

// 定义函数指针
// typedef void(*fun_t)(int);
typedef void(*fun_t)(void *,int);//基类
class Base{
public:virtual void f(int x){cout << this << endl;cout << "Base::f "<< x << endl; }virtual void g(int x){cout << this << endl;cout << "Base::g " << x << endl; }virtual void h(int x){cout << this << endl;cout << "Base::h " << x << endl;}};//子类 公有继承基类
class Derive: public Base{
public:void g(int x) override {cout << this << endl; cout << "Derive::g " << x << endl;}
};int main(void)
{cout << "sizeof(Base): " << sizeof(Base) << endl;Base b;Derive d;Base &c = d;Base *pBase = new Derive;//方法一：((fun_t**)(&b))[0][1](&c,7);((fun_t**)(&b))[1][1](&c,9);//方法二：// long *pvptr = (long*)(&b);long *pvptr = (long *)pBase;long *vptr = (long *)*pvptr;fun_t f1 = (fun_t)vptr[0];fun_t f2 = (fun_t)vptr[1];fun_t f3 = (fun_t)vptr[2];f1(&b,1);f2(&b,2);f3(&b,3);return 0;
}