C++智能指针使用

#include <map>
#include <string>
#include <iostream>
#include <memory>
class object
{
public:
	object()
	{
		std::cout <<"defaut constructor" <<std::endl;
	}
	~object()
	{
		std::cout <<"deconstructor" <<std::endl;
	}
	object(const object& other)
	{
		std::cout <<"copy constructor" <<std::endl;
	}
	object& operator=(const object& other)
	{
		std::cout <<"==========" <<std::endl;
	}
};
struct st
{
	int value;
	std::shared_ptr<object> p_obj;
	st()
	{
		std::cout <<"st defaut constructor" <<std::endl;
		value = 1;
		p_obj = nullptr;
	}
	~st()
	{
		std::cout <<"st deconstructor" <<std::endl;
	}
};
int main()
{
	std::map<int, std::shared_ptr<st>>_map;
	_map.clear();
	std::shared_ptr<object> ptr(new object);
	std::cout << ptr.use_count()<<std::endl;
	std::shared_ptr<st> tmp(new st);
	tmp->value = 2;
	tmp->p_obj = ptr;
	std::cout << ptr.use_count()<<std::endl;
	_map.insert(std::map<int, std::shared_ptr<st>>::value_type(2, tmp));
	std::cout << ptr.use_count()<<std::endl;
	//_map.erase(2);
	std::cout << ptr.use_count()<<std::endl;
	int *num = new int(23);
	std::shared_ptr<int> p1(num);
	std::shared_ptr<int> p2(num); //会崩溃
}