求助：智能指针的一个实现，不知为何在析构时出现指针无效？
程序代码：using std::endl;
#include <string>
#include <cstddef>
using std::size_t;
/* smart pointer class: takes ownership of the dynamically allocated
* object to which it is bound
* User code must dynamically allocate an object to initialize a HasPtr
* and must not delete that object; the HasPtr class will delete it
*/
//private class for use by HasPtr only
class U_Ptr {
friend class HasPtr;
int *ip;//save raw point
size_t use;//save num
U_Ptr(int *p): ip(p), use(1) { }
~U_Ptr() { delete ip; cout<<"ip已经被释放！"<<endl;}
};
class HasPtr {
public:
// HasPtr owns the pointer; p must have been dynamically allocated
HasPtr(int *p, int i): ptr(new U_Ptr(p)), val(i) { }
// copy members and increment the use count
HasPtr(const HasPtr &orig):
ptr(orig.ptr), val(orig.val) { ++ptr->use; }
HasPtr& operator=(const HasPtr&);
// if use count goes to zero, delete the U_Ptr object
~HasPtr() { if (--ptr->use == 0) delete ptr; }
friend ostream& operator<<(ostream&, const HasPtr&);
// copy control and constructors as before
// accessors must change to fetch value from U_Ptr object
int *get_ptr() const { return ptr->ip; }
int get_int() const { return val; }
// change the appropriate data member
void set_ptr(int *p) { ptr->ip = p; }
void set_int(int i) { val = i; }
// return or change the value pointed to, so ok for const objects
// Note: *ptr->ip is equivalent to *(ptr->ip)
int get_ptr_val() const { return *ptr->ip; }
void set_ptr_val(int i) { *ptr->ip = i; }
private:
U_Ptr *ptr; // points to use-counted U_Ptr class
int val;
};
HasPtr& HasPtr::operator=(const HasPtr &rhs)
{
++rhs.ptr->use; // increment use count on rhs first
if (--ptr->use == 0)
delete ptr; // if use count goes to 0 on this object, delete it
ptr = rhs.ptr; // copy the U_Ptr object
val = rhs.val; // copy the int member
return *this;
}
ostream& operator<<(ostream &os, const HasPtr &hp)
{
os << "*ptr: " << hp.get_ptr_val() << "\tval: " << hp.get_int() << endl;
return os;
}
int main()
{
int obj = 0;
HasPtr ptr1(&obj, 42);
HasPtr ptr2(ptr1);
cout << "(1) ptr1: " << ptr1 << endl << "ptr2: " << ptr2 << endl;
ptr1.set_ptr_val(42); // sets object to which both ptr1 and ptr2 point
ptr2.get_ptr_val(); // returns 42
cout << "(2) ptr1: " << ptr1 << endl << "ptr2: " << ptr2 << endl;
ptr1.set_int(0); // changes s member only in ptr1
ptr2.get_int(); // returns 42
ptr1.get_int(); // returns 0
cout << "(3) ptr1: " << ptr1 << endl << "ptr2: " << ptr2 << endl;
system("pause");
return 0;
}
