C++ shared_ptr进一步认知，为什么引用计数＞2退出作用域都可以调用析构

1.使用智能指针需要#include <memeroy>

2.上代码：

#include <memory>
#include <iostream>
using namespace std;
struct lifePeriod
{lifePeriod():a(1){cout << "无参构造！" << endl;}virtual ~lifePeriod(){cout << "析构！" << endl;}lifePeriod(const lifePeriod& d){cout << "有参构造！" << endl;}int a;
};
int main()
{{shared_ptr<lifePeriod> p5 = make_shared<lifePeriod>();cout << p5.use_count() << endl;shared_ptr<lifePeriod> p6(p5);shared_ptr<lifePeriod> p7(p6);cout << p5.use_count() << endl;cout << p6.use_count() << endl;cout << p7.use_count() << endl;}cout << "$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$-------------r$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$" << endl;
}

• 输出

无参构造！
1
3
3
3
析构！
$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$-------------r$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

3.解释：放心使用的原因，智能指针本身是模板类，离开作用域会调用析构函数，将引用计数减1，最终引用计数都会为0，释放资源