[C++知识库]c++ primer5th (未解决) hasptr定义了移动构造函数却不能使用std::move

#include <string>
#include <cstddef>
#include "hasptr.h"
using namespace std;


    HasPtr::HasPtr(const std::string &s): 
	  ps(new std::string(s)), i(0), use(new std::size_t(1)) {}

	// copy constructor copies all three data members 
	// and increments the counter
    HasPtr::HasPtr(const HasPtr &p): 
		ps(p.ps), i(p.i), use(p.use) { ++*use; }

    HasPtr::HasPtr(HasPtr &&p): ps(p.ps), i(p.i), use(p.use) 
		{ p.ps = 0; p.use = 0; }


HasPtr::~HasPtr()
{
	if (--*use == 0) {   // if the reference count goes to 0
		delete ps;       // delete the string
		delete use;      // and the counter
	}
}

HasPtr &
HasPtr::operator=(HasPtr &&rhs)
{
	if (this != &rhs) {
		if (--*use == 0) {   // do the work of the destructor
			delete ps;
			delete use;
		}
		ps = rhs.ps;         // do the work of the move constructor
		i = rhs.i;
		use = rhs.use;
		ps = 0; use = 0;
	}
	return *this;
}

HasPtr& HasPtr::operator=(const HasPtr &rhs) 
{
	++*rhs.use;  // increment the use count of the right-hand operand
	if (--*use == 0) {   // then decrement this object's counter
		delete ps;       // if no other users 
		delete use;      // free this object's allocated members
	}
	ps = rhs.ps;         // copy data from rhs into this object
	i = rhs.i;
	use = rhs.use; 
	return *this;        // return this object
}

HasPtr f(HasPtr hp) // HasPtr passed by value, so it is copied
{
	HasPtr ret;
	ret = hp;        // assignment copies the given HasPtr
	// proces ret
	return ret;      // ret and hp are destroyed
}

//hasptr.h
#include <string>
#include <iostream>
#include <new>
using namespace std;
class HasPtr{
	public:
		HasPtr(const string &s  = string());
		HasPtr(const HasPtr &);
		HasPtr& operator=(const HasPtr &);
		HasPtr(HasPtr &&);
		HasPtr& operator=(HasPtr &&);
		~HasPtr();
		size_t use_count()const
			{
			cout <<"use_count:" << *use << endl;
			return *use;
			}

	private:
		size_t    * use;
		string * ps;
		int i;
};

#include <string>
#include <new>
#include <iostream>
#include "hasptr.h"
#include <vector>
#include <algorithm>
using namespace std;
int main()
{

HasPtr h1("hasptr1");
HasPtr h2;
h2 = (h1);


	return 0;
}

编译没问题，运行后出现

Segment fault(cole dumped)

问题已经找到了，是因为变量多次释放造成的。两个赋值运算符指针释放后都佳nullptr，然后

析构函数里面首先判断下 !use是否有值，这样就安全了。