bug#16711: 24.3.50; Error: pre-redisplay-function

bug#16711: 24.3.50; Error: pre-redisplay-function

[T.V Raman]

I've been bitten by this intermitently for the last few weeks; it
appears to be happening more often now.

Observed initially in W3 when rendering heavy-weight web pages; it also
shows up in eww.

You get a variable depth exeeds max eval depth error repeatedly --
turning on debug doesn't yield any additional info.


The fix appears to be to set pre-redisplay-function to nil --- looking
at the code, I've not figured out what that variable does 



In GNU Emacs 24.3.50.2 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.10)
 of 2014-02-08 on lapdog
System Description:	Ubuntu 12.04.1 LTS

Configured using:
 `configure --prefix=/usr/local --without-compress-install'

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Summary

Minor modes in effect:
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  semantic-mode: t
  ido-everywhere: t
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Recent input:
RET y 4 g RET y n C-e s C-e a C-e m ESC [ [ D 4 g C-e 
m ESC m ESC < ESC [ C ESC [ C <down-mouse-1> <mouse-1> 
C-n ESC < C-n ESC x r e o ESC DEL r e p o r TAB b TAB 
RET

Recent messages:
nnimap read 11k from imap.gmail.com
nnimap read 29k from imap.gmail.com
nnimap read 61k from imap.gmail.com
nnimap read 87k from imap.gmail.com
nnimap read 94k from imap.gmail.com
nnimap read 112k from imap.gmail.com
Reading active file via nndraft...done
Gnus is ready 
Auto-saving...
End of buffer  [2 times]

Load-path shadows:
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/home/raman/emacs/lisp/site-lisp/vm/lisp/tapestry hides /home/raman/emacs/lisp/emacspeak/lisp/tapestry
/home/raman/emacs/lisp/emacspeak/lisp/tetris hides /usr/local/share/emacs/24.3.50/lisp/play/tetris
/home/raman/.emacs.d/elpa/js2-mode-20131119.116/.dir-locals hides /usr/local/share/emacs/24.3.50/lisp/gnus/.dir-locals

Features:
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move-toolbar gtk x-toolkit x multi-tty emacs)

-- 

bug#16711: 24.3.50; Error: pre-redisplay-function

[Stefan Monnier]

> I've been bitten by this intermitently for the last few weeks; it
> appears to be happening more often now.
> Observed initially in W3 when rendering heavy-weight web pages; it also
> shows up in eww.
> You get a variable depth exeeds max eval depth error repeatedly --

Hmm.. can you come up with a recipe to reproduce it?

> turning on debug doesn't yield any additional info.

Indeed, pre-redisplay-function is run at a time where we can't
conveniently redisplay, I think, so we can't drop into the debugger.

> The fix appears to be to set pre-redisplay-function to nil

That's obviously just a workaround.

> --- looking at the code, I've not figured out what that variable does

The variable doesn't do anything, it's just a hook.
Its default value is used to implement the highlighting of the active region.


        Stefan

bug#16711: 24.3.50; Error: pre-redisplay-function

[T. V. Raman]

loading something like cnn.com in eww appears to trigger it. But
the problem is that it doesn't *always* trigger it 
>>>>> "Stefan" == Stefan Monnier <monnier@iro.umontreal.ca> writes:
    >> I've been bitten by this intermitently for the last few
    >> weeks; it appears to be happening more often now. Observed
    >> initially in W3 when rendering heavy-weight web pages; it
    >> also shows up in eww. You get a variable depth exeeds max
    >> eval depth error repeatedly --
    Stefan> 
    Stefan> Hmm.. can you come up with a recipe to reproduce it?
    Stefan> 
    >> turning on debug doesn't yield any additional info.
    Stefan> 
    Stefan> Indeed, pre-redisplay-function is run at a time where
    Stefan> we can't conveniently redisplay, I think, so we can't
    Stefan> drop into the debugger.
    Stefan> 
    >> The fix appears to be to set pre-redisplay-function to nil
    Stefan> 
    Stefan> That's obviously just a workaround.
    Stefan> 
    >> --- looking at the code, I've not figured out what that
    >> variable does
    Stefan> 
    Stefan> The variable doesn't do anything, it's just a
    Stefan> hook. Its default value is used to implement the
    Stefan> highlighting of the active region.
    Stefan> 
    Stefan> 
    Stefan>         Stefan

bug#16711: 24.3.50; Error: pre-redisplay-function

[Lars Ingebrigtsen]

"T. V. Raman" <tv.raman.tv@gmail.com> writes:

> loading something like cnn.com in eww appears to trigger it. But
> the problem is that it doesn't *always* trigger it 

Are you still seeing this problem?  I'm unable to reproduce it.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#16711: 24.3.50; Error: pre-redisplay-function

[T. V. Raman]

1. This may not have been eww specific though eww triggered it
regularly.
My work-around was to set that var to nil -- and it's not bitten since.
>>>>> "Lars" == Lars Ingebrigtsen <larsi@gnus.org> writes:
    Lars> "T. V. Raman" <tv.raman.tv@gmail.com> writes:
    >> loading something like cnn.com in eww appears to trigger
    >> it. But the problem is that it doesn't *always* trigger it
    Lars> 
    Lars> Are you still seeing this problem? I'm unable to
    Lars> reproduce it.
    Lars> 
    Lars> -- (domestic pets only, the antidote for overdose,
    Lars> milk.) bloggy blog: http://lars.ingebrigtsen.no

bug#16711: 24.3.50; Error: pre-redisplay-function

[Lars Ingebrigtsen]

"T. V. Raman" <tv.raman.tv@gmail.com> writes:

> 1. This may not have been eww specific though eww triggered it
> regularly.
> My work-around was to set that var to nil -- and it's not bitten since.

Can you give a recipe for reproducing the bug starting from "emacs -Q"?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#16711: 24.3.50; Error: pre-redisplay-function

[T. V. Raman]

Lars, Starting from emacs -q is well-nigh impossible  for me --
as the Emacspeak Press Release says --"Once Emacspeak is
uninstalled, the user  stops functioning altogether"
>>>>> "Lars" == Lars Ingebrigtsen <larsi@gnus.org> writes:
    Lars> "T. V. Raman" <tv.raman.tv@gmail.com> writes:
    >> 1. This may not have been eww specific though eww
    >> triggered it regularly. My work-around was to set that var
    >> to nil -- and it's not bitten since.
    Lars> 
    Lars> Can you give a recipe for reproducing the bug starting
    Lars> from "emacs -Q"?
    Lars> 
    Lars> -- (domestic pets only, the antidote for overdose,
    Lars> milk.) bloggy blog: http://lars.ingebrigtsen.no

bug#16711: 24.3.50; Error: pre-redisplay-function

[Stefan Monnier]

> I've been bitten by this intermitently for the last few weeks; it
> appears to be happening more often now.
> Observed initially in W3 when rendering heavy-weight web pages; it also
> shows up in eww.

That's a problem that needs fixing.

> You get a variable depth exeeds max eval depth error repeatedly --
> turning on debug doesn't yield any additional info.

That's not very surprising: since pre-redisplay-function is run during
redisplay, running redisplay (e.g. to show a backtrace) from within it
would require extra care to try and avoid inf-looping.

Maybe we should re-introduce stack-trace-on-error, or something
equivalent, for those cases.

In the mean time, can you run Emacs within GDB and set a breakpoint on
maybe_call_debugger?


        Stefan

bug#16711: 24.3.50; Error: pre-redisplay-function

[Lars Ingebrigtsen]

"T. V. Raman" <tv.raman.tv@gmail.com> writes:

> Lars, Starting from emacs -q is well-nigh impossible  for me --
> as the Emacspeak Press Release says --"Once Emacspeak is
> uninstalled, the user  stops functioning altogether"

Yeah, I can see how that would be a problem.  :-)

eww does some funky stuff in `after-change-functions' -- could that be
interfering with something in Emacspeak, perhaps?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#16711: 24.3.50; Error: pre-redisplay-function

[T. V. Raman]

Possible -- though I am not sure. Note -- at the time I reported
this, eww wasn't the only  thing that caused it -- it just
tickled it a lot more. 
>>>>> "Lars" == Lars Ingebrigtsen <larsi@gnus.org> writes:
    Lars> "T. V. Raman" <tv.raman.tv@gmail.com> writes:
    >> Lars, Starting from emacs -q is well-nigh impossible for
    >> me -- as the Emacspeak Press Release says --"Once
    >> Emacspeak is uninstalled, the user stops functioning
    >> altogether"
    Lars> 
    Lars> Yeah, I can see how that would be a problem. :-)
    Lars> 
    Lars> eww does some funky stuff in `after-change-functions'
    Lars> -- could that be interfering with something in
    Lars> Emacspeak, perhaps?
    Lars> 
    Lars> -- (domestic pets only, the antidote for overdose,
    Lars> milk.) bloggy blog: http://lars.ingebrigtsen.no

bug#16711: 24.3.50; Error: pre-redisplay-function

[Stefan Kangas]

"T. V. Raman" <tv.raman.tv@gmail.com> writes:

> Possible -- though I am not sure. Note -- at the time I reported
> this, eww wasn't the only  thing that caused it -- it just
> tickled it a lot more.

That was 5 years ago.

It seems like that an acceptable workaround was found here, and no one
else has been able to reproduce this since.  It therefore seems unlikely
that we'll make any more progress here.

I'm therefore closing this bug report.  Let's hope that if this bothers
anyone else they will report it again and we can then see about finding
a better solution.

If this conclusion is incorrect or anyone disagrees, please reply to
this email (use "Reply to all" in your email client) and we can reopen
the bug report.

bug#16711: 24.3.50; Error: pre-redisplay-function

[Stefan Monnier]

> Possible -- though I am not sure. Note -- at the time I reported
> this, eww wasn't the only  thing that caused it -- it just
> tickled it a lot more. 

Indeed, AFAIK the `pre-redisplay-function` doesn't run any code from EWW
(nor from Emacspeak), so the problem is likely elsewhere.

If you can still reproduce the problem, the best course of action might
be to go to GDB (from outside that Emacs session), attach to the Emacs
session and set a break point in `maybe_call_debugger` and then look at
the Lisp backtrace with `xbt`.


        Stefan


>>>>>> "Lars" == Lars Ingebrigtsen <larsi@gnus.org> writes:
>     Lars> "T. V. Raman" <tv.raman.tv@gmail.com> writes:
>     >> Lars, Starting from emacs -q is well-nigh impossible for
>     >> me -- as the Emacspeak Press Release says --"Once
>     >> Emacspeak is uninstalled, the user stops functioning
>     >> altogether"
>     Lars> 
>     Lars> Yeah, I can see how that would be a problem. :-)
>     Lars> 
>     Lars> eww does some funky stuff in `after-change-functions'
>     Lars> -- could that be interfering with something in
>     Lars> Emacspeak, perhaps?
>     Lars> 
>     Lars> -- (domestic pets only, the antidote for overdose,
>     Lars> milk.) bloggy blog: http://lars.ingebrigtsen.no