return与析构续

#include <iostream>
using namespace std;
class Point{
private:
    int x,y;
public:
    Point(int a,int b=0){
        x=a;y=b;
        cout<<"normal"<<endl;
    }
    Point(const Point &p){
        x=2*p.x;
        y=2*p.y;
        cout<<"copy"<<endl;
    }
    void print(){
        cout<<x<<" "<<y<<endl;
    }
    ~Point(){
        cout<<"destructing"<<endl;
    }
};
void f1(Point p){
    p.print();
}
Point f3(Point p){
    return p;
}
Point f2(){
    Point p(10,30);
    return p;
}
int main(){
    Point p4(1,1);
    cout<<"p4"<<endl;
    p4.print();
    Point p2=f3(p4);
    p2.print();
    return 0;

}

结果：

normal
p4
1 1
copy
copy
destructing
4 4
destructing
destructing

若主函数为：

int main(){
    Point p4(1,1),p2(1,1);
    cout<<"p4"<<endl;
    p4.print();
    p2=f3(p4);
    p2.print();
    return 0;

}

结果：

normal
normal
p4
1 1
copy
copy
destructing
destructing//原来的p2析构
4 4
destructing
destructing