Are static variables in member functions shared across all instances of a class?

Static Variables in Member Functions: Understanding Their Behavior

In C , static variables within member functions behave differently than instance variables. Let's explore how they work using an example:

Consider the following class:

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

In this class, i is declared as a static variable within the foo member function. Static variables have a lifetime that persists throughout the entire program.

Now, let's consider what happens when multiple instances of class A are created:

A o1, o2, o3;

Is the static variable i shared among all instances of A, or does each instance have its own copy?

In C , static variables within member functions are shared among all instances of the class. This means that calling foo() on one instance of A increments the same i for all instances.

To illustrate this behavior:

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

In this example, each instance of A calls the foo() function, incrementing the shared static variable i.

Therefore, unlike instance variables, which are unique to each instance, static variables in member functions are a single entity shared by all instances of a class. They maintain their values throughout the lifetime of the program.

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