bug#61940: 29.0.60; Occasional crash when moving point continously with visual line numbers

[Eli Zaretskii]

> Resent-To: bug-gnu-emacs@gnu.org
> From: Simon Pugnet <simon@polaris64.net>
> Date: Fri, 03 Mar 2023 13:08:42 +0000 (2 hours, 47 minutes, 40 seconds ago)
> 
> I've recently (within the last week) noticed that Emacs will crash
> when I'm scrolling, specifically when scrolling through a fairly large
> PHP source file using either `php-mode' or `web-mode'. I'm not sure
> however if this is related to those modes or not.
> 
> By "scrolling" I mean holding down a key to move the point up or down.
> I am using Evil so this is done by holding "j" or "k".
> 
> I'm aware that this isn't very helpful for reproducing the problem
> considering that I have so many packages loaded. I've yet to be able
> to reproduce this with a simpler configuration, but I'll be sure to
> send an update if I do. I am having trouble narrowing down the
> packages to find a culprit, but it could also be that my loaded
> packages exacerbate the core issue enough to cause a crash.
> 
> In addition to this I recently noticed that key presses would
> occasionally become out of order. I would start typing something like
> "hello world" and I'd notice Emacs pause briefly, then I'd see
> something like "llohe world". This was particularly evident when using
> Evil as normal state commands like "i" (insert state) would come out
> of order, meaning that "ihello" (insert, enter "hello") might become
> "lloihe" (move right, move right, new line below and enter insert,
> enter "ihe"). I'm not sure if this is related to the crashing bug but
> it also started happening at the same time.
> 
> The reason that I think it has something to do with visual line
> numbers is that the backtrace (below) seems to be within
> `display_count_lines_visually'. Also, I've changed the line numbering
> mode to relative and I haven't experienced the crash since (although
> it's still early days).
> 
> I got the following backtrace when attaching to a running instance of
> Emacs which crashed.

I'm not sure I understand what you mean by "attaching to a running
instance of Emacs which crashed".  If Emacs crashed, then it no longer
is running, so what exactly happens when Emacs "crashes", and how do
you attach GDB to such a "crashed" session?

> Continuing from this point seems to return to `XIfEvent' which then
> ends up back in `poll' (a loop).

This backtrace just says Emacs is reading input, and that you have an
X input method enabled.  I'm not sure it tells us anything about the
crash itself.  Please run Emacs under GDB to begin with, and then try
to reproduce the crash.  When it does crash, please type at the GDB
prompt:

   thread apply all bt

and post here the output.

Let me know if you need more detailed instructions for doing the
above, or if something is unclear.

Thanks.