Re: How do I debug this?

[Mark Geary]

On Wed, 6 Sep 2017, Michael Albinus wrote:

> Mark Geary <address@hidden> writes:
>
> > I gues there is another thing which isn't exactly a problem, but is an
> > annoyance. When I'm editing a file on the FreeBSD machine. I fequently
> > get messages [falsely] warning me that the file has changed on the
> > remote host. This happened with both Emacs 23.1.1 and now with 25.2. I
> > don't think I see this when connecting to any other machine.  How does
> > Tramp check this, and do you have any ideas why it might be reporting
> > false positives?
>
> Hard to say, needs to debug. Emacs checks permanently, whether the
> associated file of a buffer has been modified from external. This is
> done by verify-visited-file-modtime, one needs to follow this
> function.
>
> If you have time, on a rainy Friday afternoon, you might want to might
> call "M-x trace-function RET verify-visited-file-modtime RET" and follow
> what happens. Likely, you need also to trace other related functions as
> well.

I suppose there is more than one cause of the false positives. One
case is where the ssh connection drops. When I update emacs's local
copy of the file, Tramp re-creates the connection to the remote machine
and tries to check the file's stats. But Tramp doesn't always
re-create the tramp_perl_file_attributes shell function.

I've attached the relevant of the debug buffer. At the beginning Tramp
detects the connection has dropped. At the end, tramp tries to use
tramp_perl_file_attributes, which fails because it wasn't re-defined
after the re-connection.

There seem to be other cases where the false positive occurs which I
am still considering.

Mark Geary

--
Fifty-four Forty or Fight!

tramp-stat-error
Description: tramp-stat-error