bug#26126: 26.0.50; file-notify-rm-watch removes arbitrary watches

[Michael Albinus]

Andreas Politz <politza@hochschule-trier.de> writes:

Hi Andreas,

> Michael Albinus <michael.albinus@gmx.de> writes:
>
>> With the returned descriptors, it cannot be decided which watch has to
>> be removed, because both descriptors are equal. So we could decide
>> either to remove all watches for a given file if such a descriptor is
>> passed to `file-notify-rm-watch', or we must adapt
>> `file-notify-add-watch' to return different descriptors. I'm undecided
>> yet.
>
> Surely, we want the ability of two or more different packages being able
> to watch the same file, without interfering with each other.  Why are
> you undecided ?

I need to dig into inotify.c. IIRC, it wasn't simple to achieve this;
that's why we have this crude solution. Maybe it could be solved only on
filenotify.el level, don't remember the details.

> I could try and find a solution, if you don't have time or anything.

I don't have time, indeed. If you want to work on this, I would
appreciate. You could always ping me if you have questions.

Pls don't forget, whatever you propose must work for at least 6
different backends: inotify, kqueue, gfilenotify, w32notify and the
remote gvfs-monitor-dir and inotifywait. Heavy tests, always.

> -ap

Best regards, Michael.