Thanks. I suggest also adding a simple "version" to the cache. Whenever you
make an incompatible change in the future, bump this version. And also make
Tramp automatically discard all cached values when they come from a
different (earlier or even a later) version. Otherwise something like this
will certainly happen again sooner or later and will cost both the person
bumping into it and you or whoever responds to the bugreport a lot of time
again.

Paul

On Fri, 30 Sept 2022 at 21:58, Michael Albinus <michael.albinus@gmx.de>
wrote:

> Version: 29.1
>
> Michael Albinus <michael.albinus@gmx.de> writes:
>
> Hi Paul,
>
> >> Yes, that fixes the problem. Does that mean I somehow have a mixup of
> >> sources from different commits (not sure how) or that the cache is
> >> persistent and can survive long times? Note that I also run Emacs 28
> >> from time to time. Could it be that 29 reuses cache created by 28 that
> >> contains no-longer-compatible values?
> >
> > Could be the latter, yes. "tmpdir" is the only cache value I know of
> > which has changed its meaning(*). Perhaps I shall add a test that it
> > ignores cached "tmpdir" values if they are remote. But hmm, it has
> > changed its meaning also in Tramp 2.5.3.2, which is distributed via GNU
> > ELPA.
>
> Pushed this change to the emacs-28 branch, it will appear in the master
> branch after merge.
>
> It will also be contained in the upcoming Tramp 2.5.3.4 on GNU
> ELPA. Closing the bug.
>
> >> Paul
>
> Best regards, Michael.
>