Question

What is special member functions in c++?

Answer 1

Special member functions[1] in C++ are functions which the compiler will automatically generate if they are used, but not declared explicitly by the programmer. The automatically generated special member functions are:

Default constructor if no other constructor is explicitly declared.

Copy constructor if no move constructor and move assignment operator are explicitly declared.

If a destructor is declared generation of a copy constructor is deprecated (C++11, proposal N3242 [2]).

Move constructor if no copy constructor, copy assignment operator, move assignment operator and destructor are explicitly declared.

Copy assignment operator if no move constructor and move assignment operator are explicitly declared.

If a destructor is declared, generation of a copy assignment operator is deprecated.

Move assignment operator if no copy constructor, copy assignment operator, move constructor and destructor are explicitly declared.

Destructor

In these cases the compiler generated versions of these functions perform a memberwise operation. For example the compiler generated destructor will destroy each sub-object (base class or member) of the object.

The compiler generated functions will be public, non-virtual[3] and the copy constructor and assignment operators will receive const& parameters (and not be of the alternative legal forms).