Re: Sigsegv on empty array intersection/subtraction

[Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>]

On Sat, 16 Nov 2013 21:48:26 +0000
Charles Daffern <seejay.11@xxxxxxxxx> wrote:
> ${:*}
> ${:|}
> 
> The missing first parameter in these expressions causes a segmentation
> fault. I'm using zsh 5.0.2 (x86_64-unknown-linux-gnu).

The following repeats a chunk in the other branch of the "if", but there
isn't an obvious common place to put it without the risk of subtle
changes of behaviour.

diff --git a/Src/subst.c b/Src/subst.c
index a4df256..1059508 100644
--- a/Src/subst.c
+++ b/Src/subst.c
@@ -2941,6 +2941,14 @@ paramsubst(LinkList l, LinkNode n, char **str, int qt, int pf_flags)
 		}
 	    }
 	}
+	if (vunset) {
+	    if (unset(UNSET)) {
+		*idend = '\0';
+		zerr("%s: parameter not set", idbeg);
+		return NULL;
+	    }
+	    val = dupstring("");
+	}
     } else {			/* no ${...=...} or anything, but possible modifiers. */
 	/*
 	 * Handler ${+...}.  TODO: strange, why do we handle this only
diff --git a/Test/D04parameter.ztst b/Test/D04parameter.ztst
index bea9459..f72a3d6 100644
--- a/Test/D04parameter.ztst
+++ b/Test/D04parameter.ztst
@@ -1551,3 +1551,12 @@
 0:Empty parameter shouldn't cause modifiers to crash the shell
 >
 >
+
+# This used to cause uncontrolled behaviour, but at best
+# you got the wrong output so the check is worth it.
+   args() { print $#; }
+   args ${:*}
+   args ${:|}
+0:Intersection and disjunction with empty parameters
+>0
+>0

-- 
Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/