fix segmentation fault for via-routes with invalid intermediate segments

CHANGELOG.md

@@ -8,6 +8,8 @@
     - API:
       - `annotations=true` now returns the data source id for each segment as `datasources`
       - Reduced semantic of merge to refer only to merges from a lane onto a motorway-like road
+    - Bugfixes
+      - Fixed an issue that would result in segfaults for viaroutes with an invalid intermediate segment when u-turns were allowed at the via-location
 
 # 5.3.0
   Changes from 5.3.0-rc.3

features/testbot/via.feature

@@ -277,3 +277,20 @@ Feature: Via points
         When I route I should get
             | from | to | route         |
             | e    | f  | ebbdcf,ebbdcf |
+
+    @2798
+    Scenario: UTurns Enabled
+        Given the node map
+            | a | b | c | d | e |
+
+        And the query options
+            | continue_straight | false |
+
+        And the ways
+            | nodes | oneway |
+            | abc   | yes    |
+            | edc   | yes    |
+
+        When I route I should get
+            | waypoints | route |
+            | a,b,e     |       |

include/engine/routing_algorithms/shortest_path.hpp

@@ -114,6 +114,10 @@ class ShortestPathRouting final
                           needs_loop_forwad,
                           needs_loop_backwards);
         }
+        // if no route is found between two parts of the via-route, the entire route becomes
+        // invalid. Adding to invalid edge weight sadly doesn't return an invalid edge weight. Here
+        // we prevent the possible overflow, faking the addition of infinity + x == infinity
+        if (new_total_distance != INVALID_EDGE_WEIGHT)
             new_total_distance += std::min(total_distance_to_forward, total_distance_to_reverse);
     }