From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Mon, 2 Oct 2017 12:51:58 +0000 (+0000)
Subject: Gracefully handle short-measure issue (Closes #3845)
X-Git-Tag: 2.4.1~22
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=cce0c7ee91d056ad2ed7f78387addc8b27dccc19;p=postgis

Gracefully handle short-measure issue (Closes #3845)



git-svn-id: http://svn.osgeo.org/postgis/branches/2.4@15872 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/NEWS b/NEWS
index 32a39f49e..4b589491a 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,7 @@ YYYY/MM/DD
  * Bug fixes *
   - #3864, Fix memory leaks in BTREE operators
   - #3869, Fix build with "gold" linker
+  - #3845, Gracefully handle short-measure issue
 
 PostGIS 2.4.0
 2017/09/30
diff --git a/liblwgeom/lwlinearreferencing.c b/liblwgeom/lwlinearreferencing.c
index fdd8c6301..5cb81bb21 100644
--- a/liblwgeom/lwlinearreferencing.c
+++ b/liblwgeom/lwlinearreferencing.c
@@ -50,14 +50,15 @@ segment_locate_along(const POINT4D *p1, const POINT4D *p2, double m, double offs
 			*pn = *p1;
 			return LW_TRUE;
 		}
-		/* If the points are different we can out.
-		   Correct behavior is probably an mprop of 0.5? */
-		lwerror("Zero measure-length line encountered!");
-		return LW_FALSE;
+		/* If the points are different we split the difference */
+		mprop = 0.5;
+	}
+	else
+	{
+		mprop = (m - m1) / (m2 - m1);
 	}
 
 	/* M is in range, new point to be generated. */
-	mprop = (m - m1) / (m2 - m1);
 	pn->x = p1->x + (p2->x - p1->x) * mprop;
 	pn->y = p1->y + (p2->y - p1->y) * mprop;
 	pn->z = p1->z + (p2->z - p1->z) * mprop;