How Do Static Variables Behave within Member Functions in C ?

Static Variables within Member Functions in C

In C , member functions can contain static variables. A static member variable within a class is shared across all instances of the class, regardless of the object on which the function is called.

Let's consider the following class:

class A {
public:
   void foo() {
      static int i;
      i++;
   }
};

Contrary to the assumption that each instance of A would have its own copy of i, it's important to note that there will be only one instance of i for the entire program. This is because static int i is declared inside the class definition and outside any specific function, making it a member of the class itself rather than a local variable to the foo function.

Hence, any instance of an A object will affect the same shared i, and its lifetime will persist throughout the program's execution. For example:

A o1, o2, o3;
o1.foo(); // i = 1
o2.foo(); // i = 2
o3.foo(); // i = 3
o1.foo(); // i = 4

In this scenario, all instances of A access and modify the same static variable i. Calling foo on any instance increments the shared i for the entire class.

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