When Does the Compiler Generate Special Member Functions in C ?

Special Member Functions Generated by Compiler

When examining the behavior of classes, it's crucial to understand the role of special member functions, also known as compiler-generated functions. These functions play a significant role in the operation of classes, but their creation is not always guaranteed.

Default Constructor

The compiler generates a default constructor under the following circumstances:

• If the user does not declare any constructor for a class.

Copy Constructor and Assignment Operator

The compiler generates a copy constructor and copy assignment operator when:

• The user does not declare them.

Destructor

The compiler generates a destructor when:

• The user does not declare it.

Additional Rules in C 11

C 11 and later versions introduce additional rules:

• Move Constructor: Generated if there are no user-declared copy constructor, copy assignment operator, or move assignment operator, the destructor is not deleted, and all members and bases are movable.
• Move Assignment Operator: Generated under similar conditions as the move constructor.

Note: All these functions are only generated if needed. If they are not used, their absence is acceptable.

Importance of Default Constructor

The default constructor plays a crucial role in enabling the inheritance mechanism in C . When a subclass inherits from a base class that has no user-defined constructor, the base class's default constructor is used to initialize the base part of the derived class object. Without a default constructor, the inheritance process cannot occur properly.

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