message: fix evaluation order dependent expression
diff: @@ -94,7 +94,8 @@ void compute_elim_forest_children_impl(const IndexType* parent, IndexType size,
  // we count the same again, this time shifted by 1 => exclusive prefix sum
  for (IndexType i = 0; i < size; i++) {
  const auto p = parent[i];
  - child[child_ptr[p + 1]++] = i;
  + child[child_ptr[p + 1]] = i;
  + child_ptr[p + 1]++;
  }
  }
  @@ -130,7 +131,9 @@ void compute_elim_forest_postorder_lvl_impl(
  postorder_idx++;
  } else {
  // otherwise go to the next child node
  - cur_node = child[first_child + current_child[cur_node]++];
  + const auto old_node = cur_node;
  + cur_node = child[first_child + current_child[old_node]];
  + current_child[old_node]++;
  level_idx++;
  }
  }
  