What does the following code do?

Question

static void llist_dtor(void *user, void *element)
{
  (void)user;
  (void)element;
  /* Do nothing */
}

Is it no-operation function? Then why is casting done? Is it ok to pass NULL as one of its parameters?

Answer 1

That's indeed a no-op. The casts to (void) are here to avoid getting "parameter never used" warnings with some compilers (the casts are optimized away, but the parameters are still considered as "used").

You can pass NULL since the parameters are ignored anyway.

Answer 2

Yes, this is a no-op function.

The casting is a common trick to prevent the compiler complaining about unused parameters.