Special Member Functions

Special member functions 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).
* 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
* The 'address of' operator (unary '&' operator)

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 and the copy constructor and assignment operators will receive const& parameters (and not be of the alternative legal forms).

Example

The following example depicts two classes: for which all special member functions are explicitly declared and for which none are declared.

#include
#include
#include

class Explicit ;

class Implicit : public Explicit ;

Signatures

Here are the signatures of the special member functions:

C++03

In C++03 before the introduction of move semantics (in C++11) the special member functions were:
* Default constructor (if no other constructor is explicitly declared)
* Copy constructor
* Copy assignment operator
* Destructor
* The 'address of' operator (unary '&' operator)

References

{{C++ programming language

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Articles with example C++ code