Check FROM arg to substring in icomplete-completions

See: http://debbugs.gnu.org/10850

2 files changed, 8 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index cc5851373b0..629b5b19d93 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2012-02-20  Leo Liu  <sdl.web@gmail.com>
+
+        * icomplete.el (icomplete-completions): Check FROM arg before
+        passing to substring (Bug#10850).
+
 2012-02-19  Chong Yidong  <cyd@gnu.org>
 
         * comint.el: Require ansi-color.
diff --git a/lisp/icomplete.el b/lisp/icomplete.el
index 80a0bf1435b..a9719651957 100644
--- a/lisp/icomplete.el
+++ b/lisp/icomplete.el
@@ -347,7 +347,9 @@ are exhibited within the square braces.)"
             (setq prospects nil)
           (while (and comps (not limit))
             (setq comp
-                  (if prefix-len (substring (car comps) prefix-len) (car comps))
+                  (if (and prefix-len (<= prefix-len (length (car comps))))
+                      (substring (car comps) prefix-len)
+                    (car comps))
                   comps (cdr comps))
             (cond ((string-equal comp "") (setq most-is-exact t))
                   ((member comp prospects))