在下面的C++代码中，在析构函数调用期间，它会崩溃，并出现以下错误。

如果打印了这条消息，至少程序还没有崩溃！但您可能还想打印其他诊断消息。DSCodes(16782,0x1000EFE00)malloc:***对象0x10742E2F0错误：未分配释放的指针DSCodes(16782,0x1000EFE00)malloc:***在malloc_error_break中设置断点以调试

有人能告诉我解构器的错误吗

class Pair {
 public:
  int *pa,*pb;
   Pair(int, int);
   Pair(const Pair &);
  ~Pair();
 };
 
Pair::Pair(int p1, int p2)
{
    this->pa = new int;
    this->pb = new int;
    *pa = p1;
    *pb = p2;
}
Pair::Pair(const Pair &obj)
{
    this->pa= new int;
    this->pb = new int;
    this->pa = obj.pa;
    this->pb = obj.pb;
}
 
Pair::~Pair()
{
    if(pa)
        delete (pa);
    if(pb)
        delete(pb);
}
 /* Here is a main() function you can use
  * to check your implementation of the
  * class Pair member functions.
  */
  
int main() {
  Pair p(15,16);
  Pair q(p);
  Pair *hp = new Pair(23,42);
  delete hp;
  
  std::cout << "If this message is printed,"
    << " at least the program hasn't crashed yet!\n"
    << "But you may want to print other diagnostic messages too." << std::endl;
  return 0;
}