void
push(T new_value)
{
  std::unique_ptr<T> new_data(new T(new_value));
  counted_node_ptr new_next;
  new_next.ptr            = new node;
  new_next.external_count = 1;
  for (;;) {
    node* const old_tail = tail.load();
    T* old_data          = nullptr;
    if (old_tail->data.compare_exchange_strong(old_data, new_data.get())) {
      old_tail->next = new_next;
      tail.store(new_next.ptr);
      new_data.release();
      break;
    }
  }
}