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

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

[Giorgos Keramidas]

Something seems to have changed in the way string-match works with its
second argument is nil.  By typing `M-x help RET' I expected to see the
same prompt that is displayed by <f1>, but instead of that a snapshot of
Emacs built from the Git mirror of the repository throws me into the
debugger at:

    Debugger entered--Lisp error: (wrong-type-argument stringp nil)
      string-match("%THIS-KEY%" nil)
      help()
      call-interactively(help t nil)
      execute-extended-command(nil)
      call-interactively(execute-extended-command nil nil)

The last changeset I have in my local Git clone is:

    commit f6829d72c1b405d6c43caa554c2123f41917e358
    Author: Chong Yidong <cyd@stupidchicken.com>
    Date:   Fri Sep 25 22:04:07 2009 +0000

        * files.el (safe-local-eval-forms): Allow time-stamp in
        before-save-hook (Bug#4554).

I'm updating a local mirror of the CVS repository now to check if this
is an artifact of the Git mirror.  In the meantime, does this seem like
a bug in `M-x help' or like something we recently changed in the
behavior of `string-match'?

In GNU Emacs 23.1.50.1 (i386-unknown-freebsd9.0, GTK+ Version 2.16.6)
 of 2009-09-26 on kobe
configured using `configure  '--prefix=/opt/emacs' '--with-x' '--with-x-toolkit=gtk' '--with-xpm' '--with-jpeg' '--with-tiff' '--with-gif' '--with-png''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: el_GR.ISO8859-7
  value of $LC_CTYPE: el_GR.ISO8859-7
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: C
  value of $XMODIFIERS: nil
  locale-coding-system: greek-iso-8bit-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  erc-list-mode: t
  erc-menu-mode: t
  erc-button-mode: t
  erc-netsplit-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-match-mode: t
  erc-notify-mode: t
  erc-autojoin-mode: t
  erc-services-mode: t
  erc-networks-mode: t
  erc-pcomplete-mode: t
  erc-ring-mode: t
  erc-log-mode: t
  erc-stamp-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  iswitchb-mode: t
  cua-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
RET C-x C-b s a RET C-x b d e m o RET C-x b n u x RET
C-x b d a r k RET C-l C-x b n u x RET C-x b s c r a
RET ESC x t o g g TAB d e b u TAB e TAB RET ESC x h
e l p RET ESC O A ESC [ 1 ; 2 B ESC [ 1 ; 2 B ESC [
1 ; 2 B ESC [ 1 ; 2 B ESC [ 1 ; 2 B ESC [ 1 ; 2 B ESC
[ 1 ; 2 B ESC w C-] RET C-y RET ESC x r e p o r t -
TAB b u TAB RET

Recent messages:
#Linux modes: +nc
#Linux was created on Tuesday 1999/03/30 04:13:13
Updating buffer list...
Formats have changed, recompiling...done
Updating buffer list...done
Commands: m, u, t, RET, g, k, S, D, Q; q to quit; h for help
Debug on Error enabled globally
Entering debugger...
Quit
Mark set

Load-path shadows:
None found.

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

[Stefan Monnier]

> 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)
 
 \f

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

[Emacs bug Tracking System]

[-- Attachment #1: Type: text/plain, Size: 953 bytes --]

Your message dated Sun, 27 Sep 2009 14:56:12 -0400
with message-id <jwvske8b4k0.fsf-monnier+emacsbugreports@gnu.org>
and subject line Re: bug#4560: 23.1.50; (string-match "string" nil) error when typing `M-x help RET'
has caused the Emacs bug report #4560,
regarding 23.1.50; (string-match "string" nil) error when typing `M-x help RET'
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what this
message is talking about, this may indicate a serious mail system
misconfiguration somewhere. Please contact owner@emacsbugs.donarmstrong.com
immediately.)


-- 
4560: http://emacsbugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=4560
Emacs Bug Tracking System
Contact owner@emacsbugs.donarmstrong.com with problems

[-- Attachment #2: Type: message/rfc822, Size: 6648 bytes --]

From: Giorgos Keramidas <keramida@ceid.upatras.gr>
To: emacs-pretest-bug@gnu.org
Subject: 23.1.50; (string-match "string" nil) error when typing `M-x help RET'
Date: Sat, 26 Sep 2009 10:52:29 +0300
Message-ID: <87ws3mjg76.fsf@kobe.laptop>

Something seems to have changed in the way string-match works with its
second argument is nil.  By typing `M-x help RET' I expected to see the
same prompt that is displayed by <f1>, but instead of that a snapshot of
Emacs built from the Git mirror of the repository throws me into the
debugger at:

    Debugger entered--Lisp error: (wrong-type-argument stringp nil)
      string-match("%THIS-KEY%" nil)
      help()
      call-interactively(help t nil)
      execute-extended-command(nil)
      call-interactively(execute-extended-command nil nil)

The last changeset I have in my local Git clone is:

    commit f6829d72c1b405d6c43caa554c2123f41917e358
    Author: Chong Yidong <cyd@stupidchicken.com>
    Date:   Fri Sep 25 22:04:07 2009 +0000

        * files.el (safe-local-eval-forms): Allow time-stamp in
        before-save-hook (Bug#4554).

I'm updating a local mirror of the CVS repository now to check if this
is an artifact of the Git mirror.  In the meantime, does this seem like
a bug in `M-x help' or like something we recently changed in the
behavior of `string-match'?

In GNU Emacs 23.1.50.1 (i386-unknown-freebsd9.0, GTK+ Version 2.16.6)
 of 2009-09-26 on kobe
configured using `configure  '--prefix=/opt/emacs' '--with-x' '--with-x-toolkit=gtk' '--with-xpm' '--with-jpeg' '--with-tiff' '--with-gif' '--with-png''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: el_GR.ISO8859-7
  value of $LC_CTYPE: el_GR.ISO8859-7
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: C
  value of $XMODIFIERS: nil
  locale-coding-system: greek-iso-8bit-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  erc-list-mode: t
  erc-menu-mode: t
  erc-button-mode: t
  erc-netsplit-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-match-mode: t
  erc-notify-mode: t
  erc-autojoin-mode: t
  erc-services-mode: t
  erc-networks-mode: t
  erc-pcomplete-mode: t
  erc-ring-mode: t
  erc-log-mode: t
  erc-stamp-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  iswitchb-mode: t
  cua-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
RET C-x C-b s a RET C-x b d e m o RET C-x b n u x RET
C-x b d a r k RET C-l C-x b n u x RET C-x b s c r a
RET ESC x t o g g TAB d e b u TAB e TAB RET ESC x h
e l p RET ESC O A ESC [ 1 ; 2 B ESC [ 1 ; 2 B ESC [
1 ; 2 B ESC [ 1 ; 2 B ESC [ 1 ; 2 B ESC [ 1 ; 2 B ESC
[ 1 ; 2 B ESC w C-] RET C-y RET ESC x r e p o r t -
TAB b u TAB RET

Recent messages:
#Linux modes: +nc
#Linux was created on Tuesday 1999/03/30 04:13:13
Updating buffer list...
Formats have changed, recompiling...done
Updating buffer list...done
Commands: m, u, t, RET, g, k, S, D, Q; q to quit; h for help
Debug on Error enabled globally
Entering debugger...
Quit
Mark set

Load-path shadows:
None found.


[-- Attachment #3: Type: message/rfc822, Size: 2091 bytes --]

From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Giorgos Keramidas <keramida@ceid.upatras.gr>
Subject: Re: bug#4560: 23.1.50; (string-match "string" nil) error when typing `M-x help RET'
Date: Sun, 27 Sep 2009 14:56:12 -0400
Message-ID: <jwvske8b4k0.fsf-monnier+emacsbugreports@gnu.org>

>>> 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,
> Thanks!  This seems to have fixed the bug :-)

Thank you for confirming,


        Stefan