I tried and the bug can happen with breakpoint set. Haven't got a backtrace
though.

I have several questions.

1. I am not familiar with GDB. I set the breakpoint by "b signal_or_quit",
is that right?

2. When I reached the breakpoint, "p current_buffer" gives me "No symbol
"current_buffer" in current context." How should I get the point position
in current window?

3. When the bug happens, the cursor doesn't jump before hitting the
breakpoint, but immediately after I continue using "c". Does this seem
right? (I guess so)

Printing the backtrace is so slow that it freezes my desktop for a long
time (and I don't know if that's forever). I need a way to tell if the bug
happens before I print the backtrace (I think that's the 2nd question
above), so I can make sure I am getting the right backtrace and leave my PC
there for a while.

在 2021年8月15日星期日，Eli Zaretskii gnu.org> 写道：

> > From: Amai Kinono <amaikinono@gmail.com>
> > Date: Sun, 15 Aug 2021 20:12:26 +0800
> > Cc: 44448@debbugs.gnu.org
> >
> > I'm on the latest commit (55772baee1627571c0814cf2d666fb3b963ff591) now.
> > Unfortunately the bug can still be reproduced on my side.
>
> If you can still reproduce it, show me the backtrace from
> signal_or_quit when the buffer is scrolled from EOB to BOB.  That
> backtrace should tell us which code still needs to be fixed.
>
> That is, set a breakpoint in signal_or_quit with the following
> commands:
>
>   backtrace
>   print current_buffer->pt
>   continue
>   end
>
> then run your recipe and press C-g until you see the problem happen.
> Then post the last few backtraces here.
>
> I can no longer reproduce the problem on my system, so I cannot do
> this myself.
>