c++编译器至少给一个类添加4个函数

1. 默认构造函数(无参，函数体为空)
2. 默认析构函数(无参，函数体为空)
3. 默认拷贝构造函数，对属性进行值拷贝
4. 赋值运算符 operator=, 对属性进行值拷贝

如果类中有属性指向堆区，做赋值操作时也会出现深浅拷贝问题

#include<iostream>
using namespace std;class Person {
public:Person(int age) {//将年龄数据开辟到堆区m_Age = new int(age);}//重载赋值运算符Person& operator=(Person& p){//应该先判断是否属性再堆区，如果有先释放干净，然后再深拷贝 if (m_Age != NULL){delete m_Age;m_Age = NULL;}//编译器提供的代码是浅拷贝//m_Age = p.m_Age;//提供深拷贝 解决浅拷贝的问题m_Age = new int(*p.m_Age); //*p.m_Age//返回自身return *this;  //this =Person operator=}~Person(){if (m_Age != NULL){delete m_Age;m_Age = NULL;}}int *m_Age;
};void test01()
{Person p1(18);Person p2(20);Person p3(30);p3 = p2 = p1;  //赋值cout << "p1的年龄为:" << *p1.m_Age << endl;cout << "p2的年龄为:" << *p2.m_Age << endl;cout << "p3的年龄为:" << *p3.m_Age << endl;}int main()
{//test01();test01();return 0;
}