禁止复制操作是否自动禁止移动操作？ [英] Does forbidding copy operations automatically forbid move operations?

问题描述

我想写一个没有任何副本和移动语义的C ++类：我只对它的构造函数和析构函数感兴趣。

我禁用复制操作构造函数和复制赋值运算符）使用C ++ 11的 = delete 语法显式地，例如：

  class MyClass 
 {
 public：
 MyClass（）{/ * Init something * /} 
〜MyClass * Cleanup something * /} 
 
 //禁用复制
 MyClass（const MyClass&）= delete; 
 MyClass& operator =（const MyClass&）= delete; 
};作为一个测试，我尝试调用 std :: move（） 
 code>在类实例上，似乎没有移动操作自动生成，因为Visual Studio 2015 C ++编译器产生错误消息。
 
 
 
这是一个特定于MSVC 2015的行为，或者是由C ++标准规定，通过 = delete 复制操作自动禁用禁用移动构造函数和移动赋值？ / p> 
 
解决方案
 MSVC符合这种情况下的标准。在C ++ 14中的[class.copy] / 9中读取：
 
 
如果类的定义 / code>没有显式地声明一个移动构造函数，当且仅当
 
 
 
 
时，将默认声明
 >  X 没有用户声明的复制构造函数 
 
  X 没有用户声明的复制赋值运算符，
 
 
  X 没有用户声明的移动赋值运算符， li> 
 
  X 没有用户声明的析构函数。
 
 
 
 < blockquote> 
 
 
所以你的类有没有移动构造函数，任何移动它的尝试都会回到删除的拷贝构造函数。
 
I want to write a C++ class without any copy and move semantics: I'm just interested in its constructor and destructor.

I disabled copy operations (i.e. copy constructor and copy assignment operator) explicitly using C++11's =delete syntax, e.g.:
class MyClass 
{
  public:    
    MyClass()  { /* Init something */    }
    ~MyClass() { /* Cleanup something */ }

    // Disable copy
    MyClass(const MyClass&) = delete;
    MyClass& operator=(const MyClass&) = delete;
};
As a test, I tried calling std::move() on class instances, and it seems that there are no move operations automatically generated, as the Visual Studio 2015 C++ compiler emits error messages.

Is this a behavior specific to MSVC 2015, or is it dictated by the C++ standard that disabling via =delete copy operations automatically disables move constructor and move assignment?
解决方案
MSVC conforms to the standard in this case. [class.copy]/9 in C++14 reads:

  
If the definition of a class X does not explicitly declare a move constructor, one will be implicitly declared
  as defaulted if and only if
  
  

  
X does not have a user-declared copy constructor,
  
X does not have a user-declared copy assignment operator,
  
X does not have a user-declared move assignment operator, and
  
X does not have a user-declared destructor.
  
So your class has no move constructor and any attempt to move it will fall back to the deleted copy constructor.

                        
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