Merge pull request #77 from mleotta/dev/exit-if-zero-tracks

Exit if zero tracks

doc/rel_notes/0.5.1.txt

@@ -64,3 +64,9 @@ Scripts
    height is larger than width.  Focal length was being interpreted
    incorrectly.  Also set the rendering image resolution based on the principal
    point to get proper aspect ratio in the camera view.
+
+Tools
+
+ * Avoid a segfault in maptk_bundle_adjust_tracks by checking that there are
+   tracks remaining after filtering by minimum length.  Provide an informative
+   message and exit cleanly if no tracks remain.

tools/bundle_adjust_tracks.cxx

@@ -652,12 +652,27 @@ static int maptk_main(int argc, char const* argv[])
   maptk::track_set_sptr tracks = maptk::read_track_file(track_file);
 
   std::cerr << "loaded "<<tracks->size()<<" tracks"<<std::endl;
+  if( tracks->size() == 0 )
+  {
+    std::cerr << "No tracks loaded."
+              << std::endl;
+    return EXIT_FAILURE;
+  }
   size_t min_track_len = config->get_value<size_t>("min_track_length");
   if( min_track_len > 1 )
   {
     boost::timer::auto_cpu_timer t("track filtering: %t sec CPU, %w sec wall\n");
     tracks = filter_tracks(tracks, min_track_len);
     std::cerr << "filtered down to "<<tracks->size()<<" long tracks"<<std::endl;
+
+    if( tracks->size() == 0 )
+    {
+      std::cerr << "All track have been filtered. "
+                << "No tracks are longer than " << min_track_len << " frames. "
+                << "Try decreasing \"min_track_len\""
+                << std::endl;
+      return EXIT_FAILURE;
+    }
   }
 
   //