bug#2370: 23.0.90; decode-coding-region make emacs crash

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

gunzip yyy.gz and eval following:

(with-temp-buffer
  (insert-file-contents-literally "~/yyy")
  (decode-coding-region (point-min) (point-max) 'undecided))


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'.
If you would like to further debug the crash, please read the file
/usr/local/share/emacs/23.0.90/etc/DEBUG for instructions.

(gdb) bt full
#0  0x28ccba07 in kill () from /lib/libc.so.7
No symbol table info available.
#1  0x0811c7e4 in fatal_error_signal (sig=11) at emacs.c:403
No locals.
#2  <signal handler called>
No symbol table info available.
#3  Fdecode_coding_region (start=Cannot access memory at address 0xbf0a2329
) at coding.c:8639
No locals.
Previous frame inner to this frame (corrupt stack?)
(gdb) xbacktrace
"decode-coding-region" (0xbfbfe070)
"progn" (0xbfbfe134)
"unwind-protect" (0xbfbfe1d4)
"save-current-buffer" (0xbfbfe284)
"with-current-buffer" (0xbfbfe304)
"let" (0xbfbfe3e4)
"with-temp-buffer" (0xbfbfe464)
"eval" (0xbfbfe508)
"eval-last-sexp-1" (0xbfbfe634)
"eval-last-sexp" (0xbfbfe7b4)
"call-interactively" (0xbfbfe974)

In GNU Emacs 23.0.90.1 (i386-unknown-freebsd7.1, GTK+ Version 2.14.7)
 of 2009-02-16 on sea.sakura.ad.jp
Windowing system distributor `Colin Harrison', version 11.0.70400002
configured using `configure  '--without-freetype' '--without-xft''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: ja_JP.eucJP
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  value of $XMODIFIERS: nil
  locale-coding-system: japanese-iso-8bit-unix
  default-enable-multibyte-characters: t

Major mode: Group

Minor modes in effect:
  gnus-topic-mode: t
  gnus-undo-mode: t
  auto-insert-mode: t
  iswitchb-mode: t
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-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
  line-number-mode: t
  transient-mark-mode: t

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