The following functions are key to making a class behave like a fundamental type and providing for easier comprehension and maintenance.

   
   class X
   {
      X();                      // default constructor
      X( const X& );            // copy constructor 
      X& operator=( const X& ); // copy assignment operator
      ~X();                     // destructor
   };

The compiler will provide default versions for some or all of these functions depending on what user declared versions exist. The behaviour of the compiler-generated default constructor is not always appropriate because it does not initialise members that are of POD type.

The behaviour of the other compiler-generated functions is satisfactory only if a class has no pointer member variables and if each of these implicitly generated functions may have public access.

Defining these functions results in a more consistent interface and a more maintainable and extensible implementation, and carries few penalties. If a class design does not require these functions then explicitly declare them private; this will prevent the compiler generated functions from being used.

A default constructor is only implicitly generated by the compiler if there is no user-declared constructor.

Rule 3.1.3

Effective C++ Item 11, 33;Industrial Strength C++ 5.11, 14.2;ISO C++ 12.1/5;