From ef243988b01a829d21c5221b88b75a86d35ce008 Mon Sep 17 00:00:00 2001
From: Daniel Baston <dbaston@gmail.com>
Date: Mon, 4 Sep 2017 00:37:56 +0000
Subject: [PATCH] #3578, Fix null return for ST_NumInteriorRings on empty
 polygon

git-svn-id: http://svn.osgeo.org/postgis/trunk@15620 b70326c6-7e19-0410-871a-916f4a2858ee
---
 postgis/lwgeom_ogc.c     | 25 +++++++++++++++++++------
 regress/tickets.sql      |  4 ++++
 regress/tickets_expected |  2 ++
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/postgis/lwgeom_ogc.c b/postgis/lwgeom_ogc.c
index 5d909c5e9..b090d7fd1 100644
--- a/postgis/lwgeom_ogc.c
+++ b/postgis/lwgeom_ogc.c
@@ -413,19 +413,32 @@ Datum LWGEOM_numinteriorrings_polygon(PG_FUNCTION_ARGS)
 {
 	GSERIALIZED *geom = PG_GETARG_GSERIALIZED_P(0);
 	LWGEOM *lwgeom = lwgeom_from_gserialized(geom);
-	LWPOLY *poly = NULL;
-	LWCURVEPOLY *curvepoly = NULL;
+
 	int result = -1;
 
 	if ( lwgeom->type == POLYGONTYPE )
 	{
-		poly = lwgeom_as_lwpoly(lwgeom);
-		result = poly->nrings - 1;
+		if (lwgeom_is_empty(lwgeom))
+		{
+			result = 0;
+		}
+		else
+		{
+			const LWPOLY *poly = lwgeom_as_lwpoly(lwgeom);
+			result = poly->nrings - 1;
+		}
 	}
 	else if ( lwgeom->type == CURVEPOLYTYPE )
 	{
-		curvepoly = lwgeom_as_lwcurvepoly(lwgeom);
-		result = curvepoly->nrings - 1;
+		if (lwgeom_is_empty(lwgeom))
+		{
+			result = 0;
+		}
+		else
+		{
+			const LWCURVEPOLY *curvepoly = lwgeom_as_lwcurvepoly(lwgeom);
+			result = curvepoly->nrings - 1;
+		}
 	}
 	
 	lwgeom_free(lwgeom);
diff --git a/regress/tickets.sql b/regress/tickets.sql
index fab5d78d8..d774c4e71 100644
--- a/regress/tickets.sql
+++ b/regress/tickets.sql
@@ -980,6 +980,10 @@ WITH clustr AS (
     SELECT '#3569', ST_CollectionHomogenize(geom)::box2d
     FROM clustr;
 
+-- #3578
+SELECT '#3578a', ST_NumInteriorRings('POLYGON EMPTY');
+SELECT '#3578b', ST_NumInteriorRings('CURVEPOLYGON EMPTY');
+
 -- #3579
 with
         params as (
diff --git a/regress/tickets_expected b/regress/tickets_expected
index 452503060..86b62a664 100644
--- a/regress/tickets_expected
+++ b/regress/tickets_expected
@@ -296,6 +296,8 @@ ERROR:  invalid KML representation
 #3470|t
 #3470b|50
 #3569|BOX(1 2,3 4)
+#3578a|0
+#3578b|0
 #3579|f|t
 #3620a|POINT(3 7)
 #3620b|POINT(2 8)
-- 
2.50.0