bug#34093: auto-save prevents quitting emacs on read-only filesystem

[Stefan Kangas]

tags 34093 + patch
thanks

Leonard Lausen <leonard@lausen.nl> writes:

> Recently my filesystem had to be emergency remounted as read-only. I
> observed that I could not kill-emacs anymore. The following showed up in
> my log upon trying to quit emacs:
>
> ```
> company-statistics--save: Opening output file: Read-only file system, 
> /home/leonard/.emacs.d/.cache/company-statistics-cache.el
> Error running timer ‘savehist-autosave’: (file-error "Opening output file" 
> "Read-only file system" "/home/leonard/.emacs.d/.cache/savehist")
> ```
>
> This prevented quitting emacs.
>
> I am not sure if `company-statistics--save` prevented the shutdown, or
> just warned about the read-only file system. Possibly the behavior of
> `company-statistics--save` is sane and only `savehist-autosave` is at
> fault. Maybe both are at fault?
>
> The expected behavior is that emacs may warn about or ignore that it
> cannot write the savehist file. Calling kill-emacs should still quit
> emacs.

I can reproduce this under "emacs -Q" by evaluating:

(progn (savehist-mode)
       (setq savehist-file "/usr/foo")
       (confirm-exit-emacs))

I have attached a patch which fixes this bug by showing a warning if
this file is not readable.

Best regards,
Stefan Kangas

0001-Fix-exiting-Emacs-when-savehist-file-not-writable.patch
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