bug#5185: 23.1; Elusive *cvs* buffer.

[Sergey Organov <sorganov@gmail.com>]

Stefan Kangas <stefan@marxist.se> writes:

> Sergei Organov <osv@javad.com> writes:
>
>> This bug is not in fact 23.1-specific. It is there, say, in 22.2.1 as
>> well.
>>
>> The cvs-update command from PCL-CVS somehow manages to create and show
>> *cvs* buffer that is not recorded in the buffer-list frame
>> parameter. I.e., the buffer *cvs*, when first created and made current
>> by cvs-update, becomes current in the only visible window in the only
>> frame, yet it is not there in the frame parameter 'buffer-list. This
>> does not happen when there are multiple windows visible in the frame. As
>> cvs-update doesn't seem to touch 'buffer-list directly, there should be
>> a bug in core emacs functions somewhere, I believe.
>>
>> To reproduce the bug one can invoke `cvs-update' over some
>> CVS-controlled directory when single window is visible, then open
>> another frame, switch to *scratch* there, and evaluate
>>
>>   (frame-parameter (next-frame) 'buffer-list)
>>
>> The result won't contain *cvs* buffer visible in the original frame.
>> Switching back to original frame and then once again to the new frame
>> will put *cvs* buffer into the list (evaluate the above once again to
>> see it). You can see this in the automatically recorded "Recent
>> messages:" at the end of this bug-report:
>>
>> (#<buffer frame-parameter.el> #<buffer  *Minibuf-1*> #<buffer *scratch*>)
>> (#<buffer *cvs*> #<buffer frame-parameter.el> #<buffer  *Minibuf-1*> #<buffer *scratch*>)
>>
>> are these two consecutive results of evaluation with switching back and
>> force between those two frames in-between.
>>
>> Even switching to mini-buffer will record *cvs* buffer into 'buffer-list
>> parameter, so one can't even use "M-x eval-expression" to see the
>> problem.
>>
>> This bug, for example, breaks the following function that is intended
>> to always switch between two recent buffers:
>>
>>   (defun switch-to-previous-buffer ()
>>     "Switch to the previous buffer."
>>     (interactive)
>>     (switch-to-buffer (other-buffer (current-buffer))))
>>
>> When this function is assigned to a key, e.g.:
>>
>>   (global-set-key [(control meta ?l)] 'switch-to-previous-buffer)
>>
>> then pressing this key twice will restore the original buffer, except
>> in case of such elusive *cvs* buffer, as first invocation of this
>> function makes *cvs* the last buffer in the list of buffers, and the
>> next invocation doesn't select it back.
>
> That was 10 years ago, and unfortunately went unanswered at the time.
> Are you still seeing this on a modern version of Emacs?  I can't
> reproduce the issue here.

No, I can't reproduce it in GNU Emacs 24.4.1 either, so the problem is
gone somewhere between 23.2.1 and 24.4.1.

I don't use CVS anymore, so didn't notice the problem disappeared. 

Best Regards,
Sergey Organov.