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.
- 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.
- Move assignment operator if no copy constructor, copy assignment operator, move constructor and destructor are explicitly declared.
- Destructor
The compiler generated functions will be
public, non-virtual and the copy constructor and assignment operators will receive const& parameters.Example
The following example depicts two classes: Explicit for which all special member functions are explicitly declared and Implicit for which none are declared.- include
- include
- include
class Implicit : public Explicit ;
Signatures
Here are the signatures of the special member functions:| Function | syntax for class MyClass |
| Default constructor | MyClass; |
| Copy constructor | MyClass; |
| Move constructor | MyClass noexcept; |
| Copy assignment operator | MyClass& operator=; |
| Move assignment operator | MyClass& operator= noexcept; |
| Destructor | ~MyClass noexcept; |
C++03
In C++03 before the introduction of move semantics the special member functions were:- Default constructor
- Copy constructor
- Copy assignment operator
- Destructor