static volatile ILister l_defaultLister_instance;
static Lock l_defaultLister_lock = new ReentrantLock;

static ILister l_defaultLister() {
  lock l_defaultLister_lock;
  if (l_defaultLister_instance == null)
    l_defaultLister_instance = unlisted(PersistentLister);
  ret l_defaultLister_instance;
}

static void l_defaultLister(ILister l) {
  lock l_defaultLister_lock;
  l_defaultLister_instance = l;
}