From 91f8b43387e1474ce1697ad6be94d354ba14323c Mon Sep 17 00:00:00 2001
From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Wed, 15 Aug 2012 18:55:56 +0000
Subject: [PATCH] Crash in ST_Distance (#1951)

git-svn-id: http://svn.osgeo.org/postgis/trunk@10183 b70326c6-7e19-0410-871a-916f4a2858ee
---
 NEWS                        |  1 +
 liblwgeom/cunit/cu_tree.c   | 13 +++++++++++++
 liblwgeom/lwgeodetic_tree.c | 31 +++++++++++++++++++++----------
 3 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/NEWS b/NEWS
index 6c8cf83b1..74a70cd04 100644
--- a/NEWS
+++ b/NEWS
@@ -44,6 +44,7 @@ PostGIS 2.1.0
            when count is zero
   - #1932, fix raster2pgsql of syntax for index tablespaces
   - #1939, remove custom data types: summarystats, histogram, quantile, valuecount
+  - #1951, remove crash on zero-length linestrings
 
 PostGIS 2.0.1
 2012/06/22
diff --git a/liblwgeom/cunit/cu_tree.c b/liblwgeom/cunit/cu_tree.c
index 04c232feb..b27a82a28 100644
--- a/liblwgeom/cunit/cu_tree.c
+++ b/liblwgeom/cunit/cu_tree.c
@@ -183,6 +183,19 @@ static void test_tree_circ_distance(void)
 	
 	spheroid_init(&s, 1.0, 1.0);
 
+	/* Ticket #1951 */
+	line = lwgeom_as_lwline(lwgeom_from_wkt("LINESTRING(0 0, 0 0)", LW_PARSER_CHECK_NONE));
+	point = lwgeom_as_lwpoint(lwgeom_from_wkt("POINT(0.1 0.1)", LW_PARSER_CHECK_NONE));
+	cline = circ_tree_new(line->points);
+	cpoint = circ_tree_new(point->point);
+	distance_tree = circ_tree_distance_tree(cpoint, cline, &s, threshold);
+	distance_geom = lwgeom_distance_spheroid((LWGEOM*)line, (LWGEOM*)point, &s, threshold);
+	circ_tree_free(cline);
+	circ_tree_free(cpoint);
+	lwline_free(line);
+	lwpoint_free(point);
+	CU_ASSERT_DOUBLE_EQUAL(distance_geom, distance_geom, 0.0001);
+
 	line = lwgeom_as_lwline(lwgeom_from_wkt("LINESTRING(-1 -1,0 -1,1 -1,1 0,1 1,0 0,-1 1,-1 0,-1 -1)", LW_PARSER_CHECK_NONE));
 	point = lwgeom_as_lwpoint(lwgeom_from_wkt("POINT(-2 0)", LW_PARSER_CHECK_NONE));
 	cline = circ_tree_new(line->points);
diff --git a/liblwgeom/lwgeodetic_tree.c b/liblwgeom/lwgeodetic_tree.c
index 5231cd700..8d892ceab 100644
--- a/liblwgeom/lwgeodetic_tree.c
+++ b/liblwgeom/lwgeodetic_tree.c
@@ -84,6 +84,22 @@ circ_node_leaf_new(const POINTARRAY* pa, int i)
 	return node;
 }
 
+/**
+* Return a point node (zero radius, referencing one point)
+*/
+static CIRC_NODE* 
+circ_node_leaf_point_new(const POINTARRAY* pa)
+{
+	CIRC_NODE* tree = lwalloc(sizeof(CIRC_NODE));
+	tree->p1 = tree->p2 = (POINT2D*)getPoint_internal(pa, 0);
+	geographic_point_init(tree->p1->x, tree->p1->y, &(tree->center));
+	tree->radius = 0.0;
+	tree->nodes = NULL;
+	tree->num_nodes = 0;
+	tree->edge_num = 0;
+	return tree;
+}
+
 /**
 * Comparing on geohash ensures that nearby nodes will be close 
 * to each other in the list.
@@ -287,16 +303,7 @@ circ_tree_new(const POINTARRAY* pa)
 		
 	/* Special handling for a single point */
 	if ( pa->npoints == 1 )
-	{
-		tree = lwalloc(sizeof(CIRC_NODE));
-		tree->p1 = tree->p2 = (POINT2D*)getPoint_internal(pa, 0);
-		geographic_point_init(tree->p1->x, tree->p1->y, &(tree->center));
-		tree->radius = 0.0;
-		tree->nodes = NULL;
-		tree->num_nodes = 0;
-		tree->edge_num = 0;
-		return tree;
-	}	
+		return circ_node_leaf_point_new(pa);
 		
 	/* First create a flat list of nodes, one per edge. */
 	num_edges = pa->npoints - 1;
@@ -308,6 +315,10 @@ circ_tree_new(const POINTARRAY* pa)
 		if ( node ) /* Not zero length? */
 			nodes[j++] = node;
 	}
+	
+	/* Special case: only zero-length edges. Make a point node. */
+	if ( j == 0 )
+		return circ_node_leaf_point_new(pa);
 
 	/* Merge the node list pairwise up into a tree */
 	tree = circ_nodes_merge(nodes, j);
-- 
2.40.0