87     LinkedListEntry<T>* tail;  member
118     if (header_->tail == nullptr) {  in push_front()
119       header_->tail = new_entry;  in push_front()
128     if (header_->tail == nullptr) {  in push_back()
129       header_->tail = header_->head = new_entry;  in push_back()
131       header_->tail->next = new_entry;  in push_back()
132       header_->tail = new_entry;  in push_back()
145       header_->tail = nullptr;  in pop_front()
164     header_->tail = nullptr;  in clear()
197         if (header_->tail == e) {  in remove_if()
198           header_->tail = p;  in remove_if()
280       header_->head = header_->tail = nullptr;  in alloc_header()