C++内存对象布局小测试

class Point2D {
public:
    Point2D(int x, int y) :x(x), y(y) {}
    Point2D(const Point2D& p) {
        cout << "copy2d" << endl;
        x = p.x, y = p.y;
    }
    virtual void print() const{
        cout << x << " " << y << endl;
    }
    virtual ~Point2D() {}
protected:
    int x;
    int y;
};
class Point3D : public Point2D {
public:
    Point3D(int x, int y, int z) :Point2D(x, y), z(z) {}
    virtual void print()const {
        cout << x << " " << y << " " << z << endl;
    }
private:
    int z;
};
int main() {
    Point2D* p2d = new Point3D(1, 2, 3);
    Point2D p2d2 = Point3D(1,2,3);//输出copy2d
    p2d->print();//1）输出为1，2，3
    p2d2.print();//2)输出为1，2
    Point2D p2d1 = *p2d;//输出copy2d
    p2d1.print();//3）输出为1，2
    (*p2d).print();//4）输出为1，2，3
    Point3D* p3d = p2d;//Point2D*类型的值不能用于初始化Point3D*类型的实体
}