基类虚函数重写调用问题

class A
{
public:
virtual void print()
{
cout<<"A class"<<endl;
}
};


class B:public A
{
virtual void print()
{
cout<<"B class"<<endl;
}

};

A a;

a.print();  //输出A class

B b;
b.print();   //输出B class

A *a=new B;
a->print();    //输出B class

B *pb=new A;//会出现错误，赋值BUG
pb->print();

若prin函数没有声明是virtual 则

A a;

a.print();  //输出A class

B b;
b.print();   //输出A class

A *a=new B;
a->print();    //输出B class

B *pb=new A;//会出现错误，赋值BUG
pb->print();