c++ - 为什么在复制分配期间调用析构函数？

Question

我定义了以下两个 C++ 结构，Room和 House . House包含 std::list<Room> .

我创建了一个 House对象 new .我创建一个新的 Room与 new .我创建了另一个 House对象 new并尝试分配之前的 House到这个。但出于某种原因 House析构函数被调用...为什么？

(然后我也遇到段错误)。

struct Room
{
   Room()
   : pString(0)
   {
     std::cout << "Room ctor [" << std::hex << this << "]\n";
   }
   Room(const Room& other)
   {
     std::cout << "Room COPY ctor [" << std::hex << this << "] other: " << std::hex << &other << "]\n";
     if(other.pString)
     {
        if(pString)
            delete pString;
        pString = strdup(other.pString);
     }
   }
   Room operator=(const Room& other)
   {
     std::cout << "Room ASSIGNMENT operator [" << std::hex << this << "] other: " << std::hex << &other << "]\n";
     if(this != &other)
     {
         if(other.pString)
         {
            if(pString)
                delete pString;
            pString = strdup(other.pString);
         }
      }
   }

  ~Room()
   { 
     std::cout << "Room dtor [" << std::hex << this << "]\n";
     if(pString)
        delete pString;
   }
   char * pString;
};

/// House struct ////////////////////////////
struct House
{
   House()
   {
     std::cout << "House ctor [" << std::hex << this << "]\n";
   }
   House(const House& other)
   {
     std::cout << "House COPY ctor [" << std::hex << this << "] other: " << std::hex << &other << "]\n";
     roomlist = other.roomlist;
   }
   House operator=(const House& other)
   {
     std::cout << "House ASSIGNMENT ctor [" << std::hex << this << "] other: " << std::hex << &other << "]\n";
     if(this != &other)
     {
       roomlist = other.roomlist;
     }
   }

  ~House()
   { 
     std::cout << "House dtor [" << std::hex << this << "]\n";
   }
   std::list<Room> roomlist;
};

测试代码如下:

       House * pCurHouse = new House;          
       Room * pIkeaRm = new Room;
       pIkeaRm->pString = strdup("IKEA ROOM");
       std::cout << "Room created\n\n\n";
       pCurHouse->roomlist.push_back(*pIkeaRm);
       House * pOtherHouse = new House;       


       std::cout << "assigning current house to this house... \n";
       *pOtherHouse = *pCurHouse;
       std::cout << "House assigned. \n\n\n";

我从来没有看到调试“House assigned”。我看到了:

assigning current house to this house... 
House ASSIGNMENT operator [0x20753a0] other: 0x2075210]
Room COPY constructor [0x2075400] other: 0x2075310]
House destructor [0x7fff36a7a6a0]   //// which House object is that????
Room destructor [0x402580]
Segmentation fault (core dumped)

Answer 1

这是 HouseHouse::operator= 方法返回值的析构函数。但是，您忘记了两个赋值运算符中的 return 语句(通常是 return *this;)，因此导致崩溃。正如 Matt McNabb 的评论中所述当然通常你也会返回一个引用，而不是一个拷贝。