bug#46397: 27.1; Cannot delete buffer pointing to a file in a path that includes a file

[Paul Eggert <eggert@cs.ucla.edu>]

On 2/11/21 2:14 PM, Matt Armstrong wrote:

> The issue isn't confined to exiting Emacs. It appears that once in a
> "tricky situation where the file can't be unlocked for whatever reason"
> Emacs will refuse to kill the buffer because unlock_file() signals an
> error.

kill-buffer already asks the user something like "Buffer XXX modified; 
kill anyway? (yes or no)" when killing a buffer that's been changed 
without being saved. Perhaps it should also ask "File XXX cannot be 
unlocked; kill buffer anyway? (yes or no)" if the file can't be unlocked.

> Note that shut_down_emacs() calls Fdo_auto_save() just before
> unlock_all_files() and that call succeeds. Fdo_auto_save() also calls
> report_file_errno, throwing an errno 13 (Permission denied), but that
> recovers and continues.

Presumably shut_down_emacs should recover and continue if 
unlock_all_files fails when it directly calls unlock_all_files.