Static functions in C

In C, functions are global by default. The “static” keyword before a function name makes it static.

For example, the below function fun() is static.

C

static int fun(void) {
  printf("I am a static function ");
}

Unlike global functions in C, access to static functions is restricted to the file where they are declared. Therefore, when we want to restrict access to functions, we make them static. Another reason for making functions static can be the reuse of the same function name in other files.

For example, if we store the following program in one file file1.c

C

/* Inside file1.c */
static void fun1(void) {
  puts("fun1 called");
}

And store the following program in another file file2.c

C

/* Inside file2.c  */
int main(void)
{
  fun1();
  getchar();
  return 0;
}

Now, if we compile the above code with the command “gcc file2.c file1.c”, we get the error “undefined reference to `fun1’”. This is because fun1() is declared static in file1.c and cannot be used in file2.c.

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