Re: gnus crashes on threads deeper than 333 articles

[Chong Yidong <cyd@stupidchicken.com>]

Chris Moore <christopher.ian.moore@gmail.com> writes:

> I just tried opening a mail folder using nnimap in gnus.
>
> One of the threads in the folder is 834 messages long, and each
> message in the thread is a reply to the previous one which results in
> the thread being 834 messages 'deep'.
>
> The definition of gnus-sort-threads in lisp/gnus/gnus-sum.el does
> this:
>     (let ((max-lisp-eval-depth 5000))
> but it doesn't increase max-specpdl-size.  Maybe it should?
>
> Or maybe it shouldn't impose fixed limits on the maximum allowable
> thread length at all.  A re-implementation using a loop instead of
> recursion should be able to get around this limit.  It's walking the
> thread tree, sorting as it goes.

The attached patch provides a reimplementation of gnus-sort-threads-1
that uses a loop instead of recursion.  It may be a little too
intricate a change to check into Emacs at this point, though.  What do
people think?

*** emacs/lisp/gnus/gnus-sum.el.~1.93.~	2006-11-24 14:49:06.000000000 -0500
--- emacs/lisp/gnus/gnus-sum.el	2006-12-03 15:25:31.000000000 -0500
***************
*** 4550,4560 ****
  	    (gnus-delete-line)))))))
  
  (defun gnus-sort-threads-1 (threads func)
!   (sort (mapcar (lambda (thread)
! 		  (cons (car thread)
! 			(and (cdr thread)
! 			     (gnus-sort-threads-1 (cdr thread) func))))
! 		threads) func))
  
  (defun gnus-sort-threads (threads)
    "Sort THREADS."
--- 4550,4569 ----
  	    (gnus-delete-line)))))))
  
  (defun gnus-sort-threads-1 (threads func)
!   (let* ((superthread (cons nil threads))
! 	 (stack (list (cons superthread threads)))
! 	 remaining-threads thread)
!     (while stack
!       (setq remaining-threads (cdr (car stack)))
!       (if remaining-threads
! 	  (progn (setq thread (car remaining-threads))
! 		 (setcdr (car stack) (cdr remaining-threads))
! 		 (if (cdr thread)
! 		     (push (cons thread (cdr thread)) stack)))
! 	(setq thread (caar stack))
! 	(setcdr thread (sort (cdr thread) func))
! 	(pop stack)))
!     (cdr superthread)))
  
  (defun gnus-sort-threads (threads)
    "Sort THREADS."