From 44757a653cb547ae7b556e8c92629d296d3c1f12 Mon Sep 17 00:00:00 2001
From: Peter Stephenson <pws@users.sourceforge.net>
Date: Tue, 22 Jan 2013 16:28:58 +0000
Subject: [PATCH] 30993: fix parameter modifier crash with :wq on empty string

---
 ChangeLog              |  8 +++++++-
 Src/subst.c            | 10 +++++++++-
 Test/D04parameter.ztst |  7 +++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/Src/subst.c b/Src/subst.c
index 974a845..a4df256 100644
--- a/Src/subst.c
+++ b/Src/subst.c
@@ -3707,6 +3707,11 @@ paramsubst(LinkList l, LinkNode n, char **str, int qt, int pf_flags)
 	char *y;
 
 	x = val;
+	if (!x) {
+	    /* Shouldn't have got here with a NULL string. */
+	    DPUTS(1, "value is NULL in paramsubst");
+	    return NULL;
+	}
 	if (prenum || postnum)
 	    x = dopadding(x, prenum, postnum, preone, postone,
 			  premul, postmul
@@ -4021,7 +4026,10 @@ modify(char **str, char **ptr)
 		    all = tmp;
 		    t = e;
 		}
-		*str = all;
+		if (!all)
+		    *str = dupstring("");
+		else
+		    *str = all;
 
 	    } else {
 		switch (c) {
diff --git a/Test/D04parameter.ztst b/Test/D04parameter.ztst
index 01f8412..bea9459 100644
--- a/Test/D04parameter.ztst
+++ b/Test/D04parameter.ztst
@@ -1544,3 +1544,10 @@
 0:Regression test for shwordsplit with null or unset IFS and quoted array
 >abc
 >a b c
+
+   foo=
+   print ${foo:wq}
+   print ${:wq}
+0:Empty parameter shouldn't cause modifiers to crash the shell
+>
+>
-- 
1.8.1.5