Subject: bug#4560: 23.1.50; (string-match "string" nil) error when typing `M-x help RET'

From: Stefan Monnier <[email-masked]>
Date: Sat, 26 Sep 2009 20:28:08 -0400

> Something seems to have changed in the way string-match works with its
> second argument is nil.

Actually, the problem was in help.el's use of make-help-screen.
I've installed the patch below, which should fix it,

        Stefan

--- lisp/help.el	14 Sep 2009 23:28:43 -0000	1.348
+++ lisp/help.el	27 Sep 2009 00:27:00 -0000
@@ -203,7 +203,9 @@
 ;; It can't find this, but nobody will look.
 (make-help-screen help-for-help-internal
   (purecopy "Type a help option: [abcCdefFgiIkKlLmnprstvw.] C-[cdefmnoptw] or ?")
-  (purecopy
+  ;; Don't purecopy this one, because it's not evaluated (it's
+  ;; directly used as a docstring in a function definition, so it'll
+  ;; be moved to the DOC file anyway: no need for purecopying it).
   "You have typed %THIS-KEY%, the help character.  Type a Help option:
 \(Use SPC or DEL to scroll through this text.  Type \\<help-map>\\[help-quit] to exit the Help command.)
 
@@ -248,7 +250,7 @@
 C-o         Emacs ordering and distribution information.
 C-p         Info about known Emacs problems.
 C-t         Emacs TODO list.
-C-w         Information on absence of warranty for GNU Emacs.")
+C-w         Information on absence of warranty for GNU Emacs."
   help-map)