When Do C Compilers Automatically Generate Move Constructors and Assignment Operators?

Automatic Generation of Move Operations in C

In C 98, the compiler could automatically generate copy constructors and copy assignment operators for classes. However, with the introduction of move semantics in C 11, questions arise about the automatic generation of move operations.

Do Move Constructors and Move Assignment Operators Automatically Generate?

No, unlike copy constructors and copy assignment operators, the compiler does not automatically generate move operations for classes with user-defined constructors or assignment operators.

Cases Where Move Operations are Not Automatically Generated

Move operations are not automatically generated if:

• The class has a user-defined constructor or copy constructor.
• The class has a user-defined assignment operator or copy assignment operator.
• The class has a non-trivial destructor.
• The class has a base class with a non-trivial destructor.
• The class contains a non-copyable or non-moveable member.

Determining Automatic Generation of Move Operations

To determine if move operations are automatically generated for a class, consider the following:

• If the class has only a default constructor and no user-defined constructors or assignment operators, move operations are generated.
• If the class has a user-defined constructor or assignment operator, you must explicitly declare the move operations.
• If the class has a non-trivial destructor or base class with a non-trivial destructor, you must explicitly declare the move operations.

Deprecation of Automatic Generation of Move Operations

In C 20, the automatic generation of move operations is deprecated if the class declares a destructor or any copy members (copy constructor, copy assignment operator). To ensure compatibility with future versions of C , it is recommended to explicitly declare move operations for classes that require them.

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