bug#991: Emacs crashes when working with unapplied diff/patch file

[Michal Kovarik <mkov01@autokelly.cz>]

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In GNU Emacs 21.4.1 (i486-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2007-06-19 on ninsei, modified by Debian
configured using `configure  '--build=i486-linux-gnu' '--host=i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' '--with-x=yes' '--with-x-toolkit=athena' 'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2''
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: en_US.UTF-8
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

I created diff/patch file (using the cvs diff) and reversed the diff afterwards, but when I opened the unapplied diff and did <enter> on the line to be added, it crashed (Segmentation fault)


Recent input:
<down-mouse-5> <mouse-5> <double-down-mouse-5> <double-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <triple-down-mouse-5> <triple-mouse-5> 
<triple-down-mouse-5> <triple-mouse-5> <triple-down-mouse-5> 
<triple-mouse-5> <prior> <prior> <prior> <prior> <prior> 
<prior> <prior> <prior> <prior> <prior> <prior> <prior> 
<prior> <prior> <prior> <prior> <prior> <prior> <prior> 
<prior> <prior> <prior> <prior> <prior> <prior> <prior> 
C-f d i f f <f3> <f3> <f3> <f3> <f3> <f3> <f3> <f3> 
<f3> <f3> <f3> <f3> <f3> <f3> <f3> <f3> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<menu-bar> <help-menu> <report-emacs-bug>

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