this is from upstream. described by:

http://mx.gw.com/pipermail/tcsh-bugs/2015-September/000978.html

and fixed by:

https://github.com/tcsh-org/tcsh/commit/86f1ca6000f81be5b3401a2ec102521cb612a518

--- tcsh-6.19.00/tw.comp.c.orig	Wed Feb  3 14:07:50 2016
+++ tcsh-6.19.00/tw.comp.c	Wed Feb  3 14:08:18 2016
@@ -251,7 +251,7 @@
 tw_match(const Char *str, const Char *pat, int exact)
 {
     const Char *estr;
-    int rv = exact ? Gmatch(str, pat) : Gnmatch(str, pat, &estr);
+    int rv = exact ? Gmatch(estr = str, pat) : Gnmatch(str, pat, &estr);
 #ifdef TDEBUG
     xprintf("G%smatch(%s, ", exact ? "" : "n", short2str(str));
     xprintf("%s, ", short2str(pat));