我可以在C ++ 98中使用复制构造函数和赋值运算符来模拟移动构造函数和移动赋值运算符功能以提高性能吗，只要我知道复制构造函数和复制赋值将仅针对代码中的临时对象调用，或者我在我的身上插入needle眼睛？

我已经举了两个例子，一个是普通的复制构造函数和复制赋值运算符，另一个是模拟移动构造函数和移动赋值运算符并在向量中推送10000个元素以调用复制构造函数。

普通副本构造函数和副本分配运算符的示例（copy.cpp）

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

class MemoryBlock
{
public:

   // Simple constructor that initializes the resource.
   explicit MemoryBlock(int length)
      : _length(length)
      , _data(new int[length])
   {
   }

   // Destructor.
   ~MemoryBlock()
   {

      if (_data != NULL)
      {
         // Delete the resource.
         delete[] _data;
      }
   }


//copy constructor.
MemoryBlock(const MemoryBlock& other): _length(other._length)
      , _data(new int[other._length])
{

      std::copy(other._data, other._data + _length, _data);
}

// copy assignment operator.
MemoryBlock& operator=(MemoryBlock& other)
{
  //implementation of copy assignment
}

private:
   int  _length; // The length of the resource.
   int*  _data; // The resource.
};


int main()
{
   // Create a vector object and add a few elements to it.
   vector<MemoryBlock> v;
   for(int i=0; i<10000;i++)
   v.push_back(MemoryBlock(i));

   // Insert a new element into the second position of the vector.
}

带有复制构造函数和复制赋值运算符的模拟移动构造函数和移动赋值运算符功能的示例（move.cpp）

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

class MemoryBlock
{
public:

   // Simple constructor that initializes the resource.
   explicit MemoryBlock(int length=0)
      : _length(length)
      , _data(new int[length])
   {
   }

   // Destructor.
   ~MemoryBlock()
   {

      if (_data != NULL)
      {
         // Delete the resource.
         delete[] _data;
      }
   }


// Move constructor.
MemoryBlock(const MemoryBlock& other)
{
   // Copy the data pointer and its length from the 
   // source object.
   _data = other._data;
   _length = other._length;
   // Release the data pointer from the source object so that
   // the destructor does not free the memory multiple times.
   (const_cast<MemoryBlock&>(other))._data  = NULL;
    //other._data=NULL;
}

// Move assignment operator.
MemoryBlock& operator=(const MemoryBlock& other)
{
   //Implementation of move constructor
   return *this;
}

private:
   int  _length; // The length of the resource.
   int*  _data; // The resource.
};


int main()
{
   // Create a vector object and add a few elements to it.
   vector<MemoryBlock> v;
   for(int i=0; i<10000;i++)
   v.push_back(MemoryBlock(i));

   // Insert a new element into the second position of the vector.
}

我观察到性能有所提高，但需要付出一些代价：

$ g++ copy.cpp -o copy
$ time ./copy 
real    0m0.155s
user    0m0.069s
sys 0m0.085s

$ g++ move.cpp -o move
$ time ./move 
real    0m0.023s
user    0m0.013s
sys 0m0.009s

我们可以观察到性能会有所提高。

• 在c ++ 98中实现移动构造函数和移动赋值运算符模拟的功能有什么陷阱，即使我确定仅在创建临时对象时才调用复制构造函数和赋值？
• 还有其他方法/技术可以在c ++ 98中实现move构造函数和赋值运算符吗？