函数内存管理？

			segTree_Node* query(int dl, int dr, segTree_Node* rt, int l, int r) {
				if (rt == NULL) return NULL;
				if (l <= dl && dr <= r) return rt;
				down(dl, dr, rt);
				int mid = (dl + dr) >> 1;
				segTree_Node* res=NULL;
				if (l <= mid) merge(query(dl, mid, rt->ls, l, r), res, res);
				if (r > mid) merge(res, query(mid + 1, dr, rt->rs, l, r), res);
				return res;
			}