Subject: 23.2; M-x help throws an error
From: Aidan Kehoe <[email-masked]>
To: [email-masked]
Date: Wed, 29 Sep 2010 00:03:05 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

This bug report will be sent to the Free Software Foundation,
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Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the [email-masked] mailing list,
and to the gnu.emacs.bug news group.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug.  If you can, give
a recipe starting from `emacs -Q':

Recipe is as follows:

1) emacs -Q
2) M-x help RET
3) Observe error giving following backtrace: 

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 issue seems to be make-help-screen in help-macro.el, which assumes
that (documentation FNAME) gives non-nil, something not true for
#'help. It would probably be sufficient to change the string-match call
like so:

  (if (and help-screen (string-match "%THIS-KEY%" help-screen))
      ...)

and an insert further down like so:

  (insert (or help-screen ""))

If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
For information about debugging Emacs, please read the file
/usr/share/emacs/23.2/etc/DEBUG.

In GNU Emacs 23.2.1 (i686-pc-cygwin, GTK+ Version 2.18.6)
 of 2010-05-08 on laptop
configured using `configure  '--srcdir=/usr/src/emacs-23.2-1/src/emacs-23.2' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--libexecdir=/usr/lib' '--datadir=/usr/share' '--localstatedir=/var' '--sysconfdir=/etc' '--datarootdir=/usr/share' '--docdir=/usr/share/doc/emacs' 'CPPFLAGS=-I/usr/include/ncursesw' 'LDFLAGS=-L/usr/lib/ncursesw' 'CC=gcc' 'CFLAGS=-O2 -pipe ' 'LIBS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: C.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
RET k C-a C-k C-x b * B A TAB C-b C-k a TAB RET c q 
C-p C-n C-p C-n C-n C-p C-p C-n C-n C-n ESC x e h l 
p C-a C-k h e l p RET f C-g q C-x o C-x b RET C-s t 
h i s C-p C-p ESC < C-s s t r i n g - m a t c h C-a 
C-x b * B a c TAB C-g C-x o ESC x h e l p RET q ESC 
x h e l p RET v C-g q ESC [ [ A v h e l p - s c r e 
e n RET C-g ESC x h e l p RET f d o c C-g q ESC [ [ 
A f d o c u m e n t a t i o n RET C-x o C-x o C-n C-n 
C-n RET RET C-p ( d o s C-b C-k c u m e n t a t i o 
n SPC ' ESC [ [ A f h e l p RET ESC [ [ A f h e l p 
- f o r - h e l p RET C-a C-e h e l p - f o r - h e 
l p - i n t e r n a l ) C-j ESC x r e p o r t - e m 
a c s - b u g RET M x - DEL DEL - x SPC h e l p SPC 
d DEL f a i l s C-b C-b C-b C-b C-b C-k R E T C-g ESC 
x h e l p RET q C-a ESC x h e ESC p ESC p RET

Recent messages:
Proceeding, will debug on next eval or call.
Entering debugger...
Continuing.
Entering debugger...
Quit
Back to top level.
Type C-x 4 C-o RET to restore the other window.
Quit
Entering debugger...
Back to top level.

Load-path shadows:
None found.

Features:
(shadow sort mail-extr message idna sendmail regexp-opt ecomplete rfc822
mml mml-sec password-cache mm-decode mm-bodies mm-encode mailcap
mail-parse rfc2231 rfc2047 rfc2045 qp ietf-drums mailabbrev nnheader
gnus-util netrc time-date mm-util mail-prsvr gmm-utils wid-edit
mailheader canlock sha1 hex-util hashcash mail-utils emacsbug byte-opt
disass bytecomp byte-compile multi-isearch find-func debug two-column cl
cl-19 help-mode easymenu view help-fns tooltip ediff-hook vc-hooks
lisp-float-type mwheel x-win x-dnd font-setting tool-bar dnd fontset
image fringe lisp-mode register page menu-bar rfn-eshadow timer select
scroll-bar mldrag mouse jit-lock font-lock syntax facemenu font-core
frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help
simple abbrev loaddefs button minibuffer faces cus-face files
text-properties overlay md5 base64 format env code-pages mule custom
widget hashtable-print-readable backquote make-network-process
font-render-setting gtk x-toolkit x multi-tty emacs)

-- 
“Apart from the nine-banded armadillo, man is the only natural host of
Mycobacterium leprae, although it can be grown in the footpads of mice.”
  -- Kumar & Clark, Clinical Medicine, summarising improbable leprosy research