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bug#5924: 23.1; accept-process-output switching current-buffer
From: |
Uday S Reddy |
Subject: |
bug#5924: 23.1; accept-process-output switching current-buffer |
Date: |
Sun, 11 Apr 2010 13:22:22 +0100 |
Stefan Monnier writes:
> > Reading the elisp manual doesn't indicate anywhere that a call such as
> > (accept-process-output process)
> > should change the current-buffer.
>
> That depends on the code run during the wait. I.e. it depends on the
> code run by the process filters, sentinels, timers, ...
Yes, indeed! If there is code being run during accept-process-output
then the state can be changed by that code. But in the example that I
witnessed, there was *no code* being run.
Looking at the manual again, it says in "Accepting Output from
Processes":
"There are *two ways* to receive the output that a subprocess
writes to its standard output stream. The output can be inserted
in a buffer, which is called the associated buffer of the process,
or a function called the "filter function" can be called to act on
the output."
In the second "way" that is being talked about, we can reasonably
expect that current-buffer might change during the execution of the
filter function. But in the first "way", where Emacs is doing all the
work of accepting the process output, I don't think it should change
the current-buffer.
> We've already fixed several bugs where process filters changed
> current-buffer, but I think we should fix it not in the process filters
> but in the code that run them. At least, unless someone can come up
> with a scenario where a process filter, sentinel, or timer would need
> to change current-buffer.
I don't fully understand this, but let me say that I am just talking
about problem with the Elisp semantics, not Emacs libraries. If a
filter function changed the current-buffer, one would regard it as
buggy. But if Elisp itself changes the current-buffer...?
The other thing that concerns me is that the same behaviour persisted
even if I set the JUST-THIS-ONE flag to t. In that case, one would
expect that Elisp would ignore the output from all other processes.
So, it should have no reason to change the current-buffer to the other
process. But it did. I am not sure if the JUST-THIS-ONE flag is
doing anything at all.
Cheers,
Uday
PS I have been looking at the emacs-developers list lately. It is
quite amazing how much the guys talk, RMS included!