Examples of errors detected by the V758 diagnostic

V758. Reference was invalidated because of destruction of the temporary object returned by the function.

OpenCV

V758 The 'graph' reference becomes invalid when smart pointer returned by a function is destroyed. utils.cpp 391

template<typename T>
struct Ptr : public std::shared_ptr<T>;
// ....
Ptr<FlannNeighborhoodGraph> FlannNeighborhoodGraph::create(....)
{
    return makePtr<FlannNeighborhoodGraphImpl>(....);
}

void Utils::densitySort (const Mat &points, int knn,
                         Mat &sorted_points, std::vector<int> &sorted_mask)
{
  // ....
  // get neighbors
  FlannNeighborhoodGraph &graph =                                  // <=
    *FlannNeighborhoodGraph::create(....);

  std::vector<double> sum_knn_distances (points_size, 0);
  for (int p = 0; p < points_size; p++) {
    const std::vector<double> &dists = graph.getNeighborsDistances(p);
    for (int k = 0; k < knn; k++)
      sum_knn_distances[p] += dists[k];
  }
  // ....
}