rule of 3 5 6 in C++

 

Rule of 3 (C++98/03)

In C++98/03, the Rule of 3 states that if a class defines one of the following special member functions, it should likely define all three:

1. Destructor: Cleans up any dynamically allocated memory or other resources.
2. Copy Constructor: Creates a new object as a copy of an existing object.
3. Copy Assignment Operator: Assigns the contents of one object to another.

Rule of 5 (C++11 and beyond)

With the introduction of C++11, the Rule of 5 builds upon the Rule of 3 and adds two more special member functions:

4. Move Constructor: Transfers resources from one object to another without copying.
5. Move Assignment Operator: Transfers resources from one object to another using move semantics rather than copying.

Rule of 6 (Extended rule, but not part of the C++ standard)

In some discussions, you may encounter references to the Rule of 6, which is an extension of the Rule of 5. It specifically addresses the issue of defining default constructor alongside the other special functions.

The Rule of 6 says that if you define any of the following special functions, you should define all six of them:

1. Destructor
2. Copy Constructor
3. Copy Assignment Operator
4. Move Constructor
5. Move Assignment Operator
6. Default Constructor

This rule helps to ensure that all necessary behaviors are correctly defined for managing resource ownership and memory management. In practice, it's more of a guideline to help developers avoid incomplete implementations when defining complex classes with custom resource management.