移动构造函数是否自动生成？ [英] Are move constructors produced automatically?

问题描述

我有一个大类持有大量的STL容器。

编译器会自动创建一个移动构造函数，将这些容器移动到目标或我必须自己做？

I have a big class holding a lot of STL containers.
Will the compiler automatically make a move constructor that will move those containers to the target or I have to make my own?

推荐答案

类X的移动构造函数隐式声明为默认

A move constructor for a class X is implicitly declared as defaulted exactly when

• 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， li>
  
• X没有用户声明的移动赋值运算符，


• X没有用户声明的析构函数，


• 移动构造函数不会隐式定义为已删除。

• 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,
• X does not have a user-declared destructor, and
• the move constructor would not be implicitly defined as deleted.

如果你的类有一个没有移动构造函数的类型数据成员，你的类不会得到一个移动构造函数，即使它没有任何复制/移动构造函数声明，因为隐式声明的move构造函数将被定义为已删除（因为该数据成员）。

So for example, if your class has a class type data member that does not have a move constructor, your class will not get a move constructor even if it doesn't have any copy/move constructor declared, because the implicitly declared move constructor would be defined as deleted (because of that data member).

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