Try to fix crash on GEOS 3.8.1 when empty coordinate sequence is returned

nyalldawson · nyalldawson · commit c27dcf4aa445 · 2020-04-30T08:31:00.000+10:00
for a point geometry Fixes #35719, fixes #35526 (cherry picked from commit 774f1db)
diff --git a/src/core/geometry/qgsgeos.cpp b/src/core/geometry/qgsgeos.cpp
@@ -1095,7 +1095,9 @@ std::unique_ptr<QgsAbstractGeometry> QgsGeos::fromGeos( const GEOSGeometry *geos
     case GEOS_POINT:                 // a point
     {
       const GEOSCoordSequence *cs = GEOSGeom_getCoordSeq_r( geosinit.ctxt, geos );
-      return std::unique_ptr<QgsAbstractGeometry>( coordSeqPoint( cs, 0, hasZ, hasM ).clone() );
+      unsigned int nPoints = 0;
+      GEOSCoordSeq_getSize_r( geosinit()->ctxt, cs, &nPoints );
+      return nPoints > 0 ? std::unique_ptr<QgsAbstractGeometry>( coordSeqPoint( cs, 0, hasZ, hasM ).clone() ) : nullptr;
     }
     case GEOS_LINESTRING:
     {
@@ -1115,7 +1117,10 @@ std::unique_ptr<QgsAbstractGeometry> QgsGeos::fromGeos( const GEOSGeometry *geos
         const GEOSCoordSequence *cs = GEOSGeom_getCoordSeq_r( geosinit.ctxt, GEOSGetGeometryN_r( geosinit.ctxt, geos, i ) );
         if ( cs )
         {
-          multiPoint->addGeometry( coordSeqPoint( cs, 0, hasZ, hasM ).clone() );
+          unsigned int nPoints = 0;
+          GEOSCoordSeq_getSize_r( geosinit()->ctxt, cs, &nPoints );
+          if ( nPoints > 0 )
+            multiPoint->addGeometry( coordSeqPoint( cs, 0, hasZ, hasM ).clone() );
         }
       }
       return std::move( multiPoint );
diff --git a/tests/src/python/test_qgsgeometry.py b/tests/src/python/test_qgsgeometry.py
@@ -5362,6 +5362,10 @@ def testLineStringFromQPolygonF(self):
         line = QgsLineString.fromQPolygonF(QPolygonF([QPointF(1.5, 2.5), QPointF(3, 4), QPointF(3, 6.5), QPointF(1.5, 2.5)]))
         self.assertEqual(line.asWkt(1), 'LineString (1.5 2.5, 3 4, 3 6.5, 1.5 2.5)')
 
+    def testGeosCrash(self):
+        # test we don't crash when geos returns a point geometry with no points
+        QgsGeometry.fromWkt('Polygon ((0 0, 1 1, 1 0, 0 0))').intersection(QgsGeometry.fromWkt('Point (42 0)')).isNull()
+
     def renderGeometry(self, geom, use_pen, as_polygon=False, as_painter_path=False):
         image = QImage(200, 200, QImage.Format_RGB32)
         image.fill(QColor(0, 0, 0))

Original file line number	Diff line number	Diff line change
`@@ -1095,7 +1095,9 @@ std::unique_ptr<QgsAbstractGeometry> QgsGeos::fromGeos( const GEOSGeometry *geos`
`1095`	`1095`	`case GEOS_POINT: // a point`
`1096`	`1096`	`{`
`1097`	`1097`	`const GEOSCoordSequence *cs = GEOSGeom_getCoordSeq_r( geosinit.ctxt, geos );`
`1098`		`- return std::unique_ptr<QgsAbstractGeometry>( coordSeqPoint( cs, 0, hasZ, hasM ).clone() );`
	`1098`	`+ unsigned int nPoints = 0;`
	`1099`	`+ GEOSCoordSeq_getSize_r( geosinit()->ctxt, cs, &nPoints );`
	`1100`	`+ return nPoints > 0 ? std::unique_ptr<QgsAbstractGeometry>( coordSeqPoint( cs, 0, hasZ, hasM ).clone() ) : nullptr;`
`1099`	`1101`	`}`
`1100`	`1102`	`case GEOS_LINESTRING:`
`1101`	`1103`	`{`
`@@ -1115,7 +1117,10 @@ std::unique_ptr<QgsAbstractGeometry> QgsGeos::fromGeos( const GEOSGeometry *geos`
`1115`	`1117`	`const GEOSCoordSequence *cs = GEOSGeom_getCoordSeq_r( geosinit.ctxt, GEOSGetGeometryN_r( geosinit.ctxt, geos, i ) );`
`1116`	`1118`	`if ( cs )`
`1117`	`1119`	`{`
`1118`		`- multiPoint->addGeometry( coordSeqPoint( cs, 0, hasZ, hasM ).clone() );`
	`1120`	`+ unsigned int nPoints = 0;`
	`1121`	`+ GEOSCoordSeq_getSize_r( geosinit()->ctxt, cs, &nPoints );`
	`1122`	`+ if ( nPoints > 0 )`
	`1123`	`+ multiPoint->addGeometry( coordSeqPoint( cs, 0, hasZ, hasM ).clone() );`
`1119`	`1124`	`}`
`1120`	`1125`	`}`
`1121`	`1126`	`return std::move( multiPoint );`