The following function reverse() is supposed to reverse a singly linked list. There is one line missing at the end of the function.

/* Link list node */
struct node
{
  int data;
  struct node* next;
};

/* head_ref is a double pointer which points to head (or start) pointer of linked list */
static void reverse(struct node** head_ref)
{
  struct node* prev   = NULL;
  struct node* current = *head_ref;
  struct node* next;
  while (current != NULL)
  {
    next  = current->next;
    current->next = prev;
    prev = current;
    current = next;
  }
  /*ADD A STATEMENT HERE*/
}

What should be added in place of /*ADD A STATEMENT HERE*/, so that the function correctly reverses a linked list.