bug#58954: 28.2; ibuffer.el out of range error on lots of buffers?

bug#58954: 28.2; ibuffer.el out of range error on lots of buffers?

[Chris Hecker]

I was getting Args out of range: #<buffer *Ibuffer*>, 51267, 51313
when hitting C-x C-b with a ton of buffers open, lots of tramp buffers,
some eww buffers, etc.

  722 buffers    86533321   669 files, 2 processes

It's too much for me to try to repro for me right now with emacs -Q, but
hopefully this will help:

I debugged it to line 1980 in release 28.2 ibuffer.el in function
ibuffer-map-lines:

    (delete-region (line-beginning-position)
        (1+ (line-end-position)))

(line-end-position) evaluated to the end of the buffer, so 1+'ing it
made delete-region error.  Changing it to:

    (delete-region (line-beginning-position)
        (min (point-max) (1+ (line-end-position))))

made ibuffer work again.  I didn't look to closely to know if this was
the result of some logic error earlier in the function, or if this 
should have a
min guard on it normally or what.

Thanks,
Chris



In GNU Emacs 28.2 (build 2, x86_64-w64-mingw32)
  of 2022-09-13 built on AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.19044
System Description: Microsoft Windows 10 Home (v10.0.2009.19044.2130)

Configured using:
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bug#58954: 28.2; ibuffer.el out of range error on lots of buffers?

[Stefan Kangas]

"Chris Hecker" <checker@d6.com> writes:

> I was getting Args out of range: #<buffer *Ibuffer*>, 51267, 51313
> when hitting C-x C-b with a ton of buffers open, lots of tramp
> buffers, some eww buffers, etc.
>
>   722 buffers 86533321 669 files, 2 processes

I can't reproduce that here.

> It's too much for me to try to repro for me right now with emacs -Q,
> but hopefully this will help:
>
> I debugged it to line 1980 in release 28.2 ibuffer.el in function
> ibuffer-map-lines:
>
>     (delete-region (line-beginning-position)
>         (1+ (line-end-position)))
>
> (line-end-position) evaluated to the end of the buffer, so 1+'ing it
> made delete-region error.  Changing it to:
>
>     (delete-region (line-beginning-position)
>         (min (point-max) (1+ (line-end-position))))
>
> made ibuffer work again.  I didn't look to closely to know if this was
> the result of some logic error earlier in the function, or if this
> should have a min guard on it normally or what.

The fix looks simple enough, but I'm uneasy about it.

`ibuffer-map-lines' seems to be mapping over buffers in *Ibuffer*, but
the last line in that buffer is not a buffer.  I have:

     600 buffers 44145326 489 files, 1 process

So my question is why `ibuffer-map-lines' is mapping over that last line
in your case?  Could you perhaps try stepping through this function
using edebug to figure out what might be going on?