The role of static in c++

The role of static in C

In C, the static keyword is used to control the scope and life cycle of variables, functions and classes.

Variables

• Variables declared as static inside a function are called static local variables.
• Static local variables are initialized the first time the function is executed and remain throughout the life cycle of the function.
• The value of a static local variable remains unchanged even if the function returns or leaves its scope.

Function

• A function declared as static outside a class is called a static member function.
• Static member functions can only access static member variables of the class and cannot access non-static member variables.
• Static member functions cannot operate on this pointer.

Class

• Use the static keyword in a class declaration to create static member variables.
• Static member variables exist throughout the life cycle of the program, even if no instance of the class is created.
• Static member variables are shared among all instances of the class.

Other usage

• Type Inlining(Type Inlining): static member functions can be inlined into the class definition to improve performance.
• Function Inlining: Static functions can be inlined into the functions that call them, avoiding the overhead of function calls.
• Constant Definition: Using the static keyword in a constexpr expression creates a constant that is known even at runtime.

Summary

• The static keyword can control the scope and life cycle of variables, functions and classes in C.
• Static local variables remain unchanged throughout the life cycle of the function.
• Static member functions can only access static member variables of the class and cannot operate on the this pointer.
• Static member variables are shared among all instances of the class.
• The static keyword is used for other purposes, such as type inlining, function inlining, and constant definition.

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