Back trace and theory for long standing foreign server bug.

[Jan Vroonhof <vroonhof@math.ethz.ch>]

Lars,

This has been bugging me since 5.2.x or so. The symptom used to be
empty summary buffers, but now I get a true error.  I guess it is time
to post a backtrace, since I heard you are still puzzeled about it.

The version: 5.6.1
The background: I have a rlogin nttp server , rloginning to host
	rulil0.leidenunv.nl, group made with G m ages ago.
The Paramters:
 (nntp "rulil0.leidenuniv.nl"
      (nntp-open-server-function nntp-open-rlogin)
      (nntp-open-connection-function nntp-open-rlogin))
The action:
   Visiting a subscribed group from this server the first time in this 
   session, causing it to open the server.

The symptoms [note, possible cause below]:

Signaling: (wrong-type-argument number-char-or-marker-p nil)
  gnus-summary-limit-children(([1214 "Re: Stolen Sex video of Pamela Anderson, download it free here !!!!!!" "karel@earthwithoutspam.net (´¯`·.¸¸. Karel .¸¸.·´¯`)" "Sat, 14 Mar 1998 18:49:17 GMT" "<350a99e1.739765@news.worldonline.nl>" "<6edu5e$6o4$2@news.worldonline.nl>" 2104 22 "Xref: highway.leidenuniv.nl nl.markt.overig:14867 nl.markt.vervoer:3920 nl.markt.wonen:4608 nl.media.krant:4136 nl.media.radio:10791 nl.media.tv:17006 nl.misc:93691 nl.motorfiets:51169 nl.muziek:32662 nl.naturisme:1705 nl.newsgroups:28069 nl.o+w.aio:1214 nl.onderwijs.nieuwe-media:141 nl.politiek:49923 "]))
  #<compiled-function (from "gnus-sum.elc") (node) "...(50)" [node nil thread nodes gnus-thread-expunge-below gnus-thread-total-score gnus-expunge-thread gnus-summary-limit-children] 3>(<6edu5e$6o4$2@news\.worldonline\.nl>)
  mapatoms(#<compiled-function (from "gnus-sum.elc") (node) "...(50)" [node nil thread nodes gnus-thread-expunge-below gnus-thread-total-score gnus-expunge-thread gnus-summary-limit-children] 3> [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ...])
  gnus-summary-initial-limit(nil)
  gnus-summary-read-group-1("nntp+rulil0.leidenuniv.nl:nl.o+w.aio" nil t nil nil)
  gnus-summary-read-group("nntp+rulil0.leidenuniv.nl:nl.o+w.aio" nil t nil nil)
  gnus-group-read-group(nil t)
  gnus-group-select-group(nil)
  gnus-topic-select-group(nil)
  call-interactively(gnus-topic-select-group)

Further info:

Stepping through with edebug (I tried this around 5.2.x time but then
edebug got confused by the heavy use of cl macros) learned that the
error comes from line 6290 in gnus-summary.el:

 (incf gnus-newsgroup-expunged-tally)

Now if I change the defvar default value for this variable from nil to 
0 then the crash goes away but the first summary buffer comes up empty 
just like I used to have before. Now this is silly since
gnus-newsgroup-expunged-tally is not really used anywhere. However
this is probably a clue.

C-h v gives 
	`gnus-newsgroup-expunged-tally' is a variable declared in Lisp.
	-- loaded from "gnus-sum"

	Value: 0

	This value is specific to the current buffer.

	Default-value: 2

Now there actualy were 2 articles expunged from this particular
newsgroup. Somehow the wrong value was set.

The theory:

For some reason (to do with rlogin servers?) gnus-summary-limit
children (and may be other critical functions are run with the wrong
current buffer.

ciao,

Jan