From 2182c81858087abe1934e112f0e5c7d96b8138b4 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Ra=C3=BAl=20Mar=C3=ADn=20Rodr=C3=ADguez?=
 <rmrodriguez@carto.com>
Date: Tue, 2 Oct 2018 09:38:48 +0000
Subject: [PATCH] Fix undefined behaviour in SADFWrite

Also addresses several GCC warnings.

Closes #4189
Closes https://github.com/postgis/postgis/pull/310


git-svn-id: http://svn.osgeo.org/postgis/trunk@16863 b70326c6-7e19-0410-871a-916f4a2858ee
---
 NEWS                    | 1 +
 liblwgeom/lwutil.c      | 8 ++++----
 loader/pgsql2shp-core.c | 2 +-
 loader/safileio.c       | 5 +++--
 4 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/NEWS b/NEWS
index 7423db1f3..3c55f4541 100644
--- a/NEWS
+++ b/NEWS
@@ -21,6 +21,7 @@ PostGIS 3.0.0
   - #4181, St_AsMVTGeom: Avoid type changes due to validation (Raúl Marín)
   - #4183, St_AsMVTGeom: Drop invalid geometries after simplification (Raúl Marín)
   - #4188, Avoid division by zero in kmeans (Raúl Marín)
+  - #4189, Fix undefined behaviour in SADFWrite (Raúl Marín)
 
 PostGIS 2.5.0
 2018/09/23
diff --git a/liblwgeom/lwutil.c b/liblwgeom/lwutil.c
index b9a523c66..52f172007 100644
--- a/liblwgeom/lwutil.c
+++ b/liblwgeom/lwutil.c
@@ -280,13 +280,13 @@ char *lwmessage_truncate(char *str, int startpos, int endpos, int maxlength, int
 			{
 				/* Add "..." prefix */
 				outstart = str + endpos + 1 - maxlength + 3;
-				strncat(output, "...", 3);
+				strncat(output, "...", 4);
 				strncat(output, outstart, maxlength - 3);
 			}
 			else
 			{
 				/* maxlength is too small; just output "..." */
-				strncat(output, "...", 3);
+				strncat(output, "...", 4);
 			}
 		}
 	}
@@ -307,12 +307,12 @@ char *lwmessage_truncate(char *str, int startpos, int endpos, int maxlength, int
 				/* Add "..." suffix */
 				outstart = str + startpos;
 				strncat(output, outstart, maxlength - 3);
-				strncat(output, "...", 3);
+				strncat(output, "...", 4);
 			}
 			else
 			{
 				/* maxlength is too small; just output "..." */
-				strncat(output, "...", 3);
+				strncat(output, "...", 4);
 			}
 		}
 	}
diff --git a/loader/pgsql2shp-core.c b/loader/pgsql2shp-core.c
index ffbc613c6..aa9c26b5e 100644
--- a/loader/pgsql2shp-core.c
+++ b/loader/pgsql2shp-core.c
@@ -1549,7 +1549,7 @@ ShpDumperOpenTable(SHPDUMPERSTATE *state)
 		{
 			if (!strncasecmp(dbffieldname, state->dbffieldnames[j], 10))
 			{
-				sprintf(dbffieldname, "%.7s_%.2d", ptr, tmpint % 100);
+				sprintf(dbffieldname, "%.7s_%.2d", ptr, abs(tmpint) % 100);
 				tmpint++;
 				continue;
 			}
diff --git a/loader/safileio.c b/loader/safileio.c
index 439ebb141..ee5a98afb 100644
--- a/loader/safileio.c
+++ b/loader/safileio.c
@@ -115,8 +115,9 @@ SAOffset SADFRead( void *p, SAOffset size, SAOffset nmemb, SAFile file )
 SAOffset SADFWrite( void *p, SAOffset size, SAOffset nmemb, SAFile file )
 
 {
-    return (SAOffset) fwrite( p, (size_t) size, (size_t) nmemb,
-                              (FILE *) file );
+	if (!nmemb || !p) return 0;
+	return (SAOffset) fwrite( p, (size_t) size, (size_t) nmemb,
+				(FILE *) file );
 }
 
 /************************************************************************/
-- 
2.40.0