Fix a crash when running 'snap geometries to layer'

A crash may happen when running the alg with 'snap to anchor nodes (single layer only)' behavior. It turns out that I made a mistake while porting the algorithm to std::sort - originally the sorting function used -1/0/+1 for comparison, while std::sort wants '<' operator returning true/false. Due to inconsistent results from the comparison function, std::sort would end up corrupting the array and memory even beyond the range, causing crashes. Related to #29400 (but does not fix it)
qgis · Jun 7, 2019 · 0ba99af · 0ba99af
1 parent 2a9028a
commit 0ba99af
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/src/analysis/vector/qgsgeometrysnappersinglesource.cpp b/src/analysis/vector/qgsgeometrysnappersinglesource.cpp
@@ -244,9 +244,9 @@ static bool snapLineString( QgsLineString *linestring, QgsSpatialIndex &index, Q
     if ( !newVerticesAlongSegment.isEmpty() )
     {
       // sort by distance along the segment
-      std::sort( newVerticesAlongSegment.begin(), newVerticesAlongSegment.end(), []( AnchorAlongSegment p1, AnchorAlongSegment p2 )
+      std::sort( newVerticesAlongSegment.begin(), newVerticesAlongSegment.end(), []( const AnchorAlongSegment & p1, const AnchorAlongSegment & p2 )
       {
-        return ( p1.along < p2.along ? -1 : ( p1.along > p2.along ) );
+        return p1.along < p2.along;
       } );
 
       // insert new vertices