bug in pop3.el?

[Vladimir Volovich <vvv@vvv.vsu.ru>]

The following message is a courtesy copy of an article
that has been posted to gnu.emacs.gnus as well.

Hi!

i use pop3 to fetch mail from our POP3 server. when i happen to
receive mail with content-transfer-encoding=8bit, and there are
certain combinations of bytes in the message being received, i get an
annoying warning:

"The target text contains the following non ASCII character(s):" and
i'm asked to select a coding system to use to encode them. This often
happens e.g. for messages in utf-8 encoding.

Evidently, something is going wrong here, as pop3.el MUST NOT bother
with encoding of characters in message bodies: it should just put
everything AS IS, byte by byte; it is gnus' previewer which should
bother with encoding of raw 8-bit bytes in message bodies to certain
coding systems according to message headers!

i've set debug-on-entry for select-safe-coding-system and here is a
backtrace:

Entering:
* select-safe-coding-system(1 747 cyrillic-iso-8bit)
  write-region(1 747 "~/.emacs-mail-crash-box" t nomesg)
  pop3-movemail("~/.emacs-mail-crash-box")
  mail-source-fetch-pop((pop :server "..." :user "..." :port "pop3" :password "...") (lambda (file orig-file) (nnmail-split-incoming file (quote nnmbox-save-mail) (quote #[nil "..." [in-buf nnmbox-mbox-buffer nnmbox-group-alist nnmbox-active-file insert-buffer-substring nnmbox-save-active] 3]) (nnmail-get-split-group orig-file source) (quote nnmbox-active-number))))
  funcall(mail-source-fetch-pop (pop :server "..." :user "..." :port "pop3" :password "...") (lambda (file orig-file) (nnmail-split-incoming file (quote nnmbox-save-mail) (quote #[nil "..." [in-buf nnmbox-mbox-buffer nnmbox-group-alist nnmbox-active-file insert-buffer-substring nnmbox-save-active] 3]) (nnmail-get-split-group orig-file source) (quote nnmbox-active-number))))
  mail-source-fetch((pop :server "..." :user "..." :port "pop3" :password "...") (lambda (file orig-file) (nnmail-split-incoming file (quote nnmbox-save-mail) (quote #[nil "..." [in-buf nnmbox-mbox-buffer nnmbox-group-alist nnmbox-active-file insert-buffer-substring nnmbox-save-active] 3]) (nnmail-get-split-group orig-file source) (quote nnmbox-active-number))))
  nnmail-get-new-mail(nnmbox #[nil "..." [nnmbox-mbox-buffer nnmbox-save-buffer] 1] "/home/vvv/" nil #[nil "..." [in-buf nnmbox-mbox-buffer nnmbox-group-alist nnmbox-active-file insert-buffer-substring nnmbox-save-active] 3])
  nnmbox-request-scan(nil "")
  gnus-request-scan(nil (nnmbox ""))
  gnus-read-active-file-1((nnmbox "") nil)
  gnus-read-active-file()
  gnus-group-get-new-news(nil)
  call-interactively(gnus-group-get-new-news)

Best,
v.