From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Wed, 11 Oct 2017 14:05:25 +0000 (+0000)
Subject: Fix rare missing boxes in geometry subdivision
X-Git-Tag: 2.4.1~8
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bef5a6156771ef87c41c82cae7a25a727ef37d26;p=postgis

Fix rare missing boxes in geometry subdivision
References #3886


git-svn-id: http://svn.osgeo.org/postgis/branches/2.4@15965 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/NEWS b/NEWS
index f18bde957..ac4ca807f 100644
--- a/NEWS
+++ b/NEWS
@@ -15,6 +15,7 @@ YYYY/MM/DD
   - #3882, undefined behaviour in zigzag with negative inputs
   - #3891, undefined behaviour in pointarray_to_encoded_polyline
   - #3895, throw error on malformed WKB input
+  - #3886, fix rare missing boxes in geometry subdivision
 
 
 PostGIS 2.4.0
diff --git a/liblwgeom/lwgeom_geos.c b/liblwgeom/lwgeom_geos.c
index 14799810f..1d3ccf707 100644
--- a/liblwgeom/lwgeom_geos.c
+++ b/liblwgeom/lwgeom_geos.c
@@ -262,19 +262,25 @@ ptarray_to_GEOSLinearRing(const POINTARRAY *pa, int autofix)
 
 	if ( autofix )
 	{
-		/* check ring for being closed and fix if not */
-		if ( ! ptarray_is_closed_2d(pa) )
+		if (pa->npoints < 1)
 		{
-			npa = ptarray_addPoint(pa, getPoint_internal(pa, 0), FLAGS_NDIMS(pa->flags), pa->npoints);
-			pa = npa;
+			lwerror("ptarray_to_GEOSLinearRing called with autofix and 0 vertices in ring, cannot fix");
 		}
-		/* TODO: check ring for having at least 4 vertices */
-#if 0
+
+		/*
+		* Check ring for being closed and fix if not.
+		* Also create a copy of geometry to operate on.
+		*/
+		if ( ! ptarray_is_closed_2d(pa) || pa->npoints < 4 )
+		{
+			pa = ptarray_addPoint(pa, getPoint_internal(pa, 0), FLAGS_NDIMS(pa->flags), pa->npoints);
+			npa = pa;
+		}
+		/* Check ring for having at least 4 vertices */
 		while ( pa->npoints < 4 )
 		{
-			npa = ptarray_addPoint(npa, getPoint_internal(pa, 0), FLAGS_NDIMS(pa->flags), pa->npoints);
+			ptarray_append_point(pa, getPoint_internal(pa, 0), LW_TRUE);
 		}
-#endif
 	}
 
 	sq = ptarray_to_GEOSCoordSeq(pa);