关于C++中拷贝构造函数

#include<iostream.h>
class point
{
public:
    point(int xx=0,int yy=0) {X=xx;Y=yy;}
    point(point &p);
    int getX() {return X;}
    int getY() {return Y;}
private:
    int X,Y;
};
point::point(point &p)
{
    X=p.X;
    Y=P.Y;
    cout<<"拷贝函数被调用"<<endl;
}
void fun1(point p)
{cout<<p.getX()<<endl;}
point fun2()
{
    point A(1,2);
        return A;
}
void main()
{
    point A(4,5);
    point B(A);
    cout<<B.getX()<<endl;
    fun1(B);
    B=fun2();
    cout<<B.getX()<<endl;
}
为什么运行会出错呢 并且point::point(point &p)
{
    X=p.X;
    Y=P.Y;
    cout<<"拷贝函数被调用"<<endl;
}
我也不太明白啊  请教高手给讲解下  谢谢啊