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