* Change in backup-buffer: how to interpret?
@ 2002-12-30 20:53 Kai Großjohann
2002-12-30 20:58 ` Kai Großjohann
2003-01-01 16:46 ` Richard Stallman
0 siblings, 2 replies; 3+ messages in thread
From: Kai Großjohann @ 2002-12-30 20:53 UTC (permalink / raw)
Cc: Michael.Albinus
Between Emacs 21.2.93 and the current CVS, I see the following change
in backup-buffer. (Actually, more stuff has changed.)
@@ -2147,13 +2356,17 @@
(defun backup-buffer ()
"Make a backup of the disk file visited by the current buffer, if appropriate.
This is normally done before saving the buffer the first time.
-If the value is non-nil, it is the result of `file-modes' on the original
-file; this means that the caller, after saving the buffer, should change
-the modes of the new file to agree with the old modes.
A backup may be done by renaming or by copying; see documentation of
variable `make-backup-files'. If it's done by renaming, then the file is
-no longer accessible under its old name."
+no longer accessible under its old name.
+
+The value is non-nil after a backup was made by renaming.
+It has the form (MODES . BACKUPNAME).
+MODES is the result of `file-modes' on the original
+file; this means that the caller, after saving the buffer, should change
+the modes of the new file to agree with the old modes.
+BACKUPNAME is the backup file name, which is the old file renamed."
(if (and make-backup-files (not backup-inhibited)
(not buffer-backed-up)
(file-exists-p buffer-file-name)
@@ -2179,12 +2392,15 @@
(or (eq delete-old-versions t) (eq delete-old-versions nil))
(or delete-old-versions
(y-or-n-p (format "Delete excess backup versions of %s? "
- real-file-name))))))
+ real-file-name)))))
+ (modes (file-modes buffer-file-name)))
;; Actually write the back up file.
(condition-case ()
(if (or file-precious-flag
; (file-symlink-p buffer-file-name)
backup-by-copying
+ ;; Don't rename a suid or sgid file.
+ (< 0 (logand modes #o6000))
(and backup-by-copying-when-linked
(> (file-nlinks real-file-name) 1))
(and (or backup-by-copying-when-mismatch
As you can see, `modes' is the result of (file-modes
buffer-file-name), and later on (logand modes #o6000) is then
invoked.
I think that file-modes can return nil. (Ange-FTP always returns
nil.) Then the logand will fail.
So is it a bug in the current code (which should deal with a nil
return value of file-modes), or is it a bug in Ange-FTP (which
returns nil)?
--
Ambibibentists unite!
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Change in backup-buffer: how to interpret?
2002-12-30 20:53 Change in backup-buffer: how to interpret? Kai Großjohann
@ 2002-12-30 20:58 ` Kai Großjohann
2003-01-01 16:46 ` Richard Stallman
1 sibling, 0 replies; 3+ messages in thread
From: Kai Großjohann @ 2002-12-30 20:58 UTC (permalink / raw)
kai.grossjohann@uni-duisburg.de (Kai Großjohann) writes:
> So is it a bug in the current code (which should deal with a nil
> return value of file-modes), or is it a bug in Ange-FTP (which
> returns nil)?
I think it would be a good idea to augment the documentation for
filename handlers. Each operation should say what a filename handler
should do when it doesn't know.
Eg, I think that file-attributes is supposed to return -1 as a
don't-know value for uid and gid, and (0 0) as a don't-know value for
access, modification, and status change time. But maybe I'm wrong --
that's even more of a reason for documentation ;-)
--
Ambibibentists unite!
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Change in backup-buffer: how to interpret?
2002-12-30 20:53 Change in backup-buffer: how to interpret? Kai Großjohann
2002-12-30 20:58 ` Kai Großjohann
@ 2003-01-01 16:46 ` Richard Stallman
1 sibling, 0 replies; 3+ messages in thread
From: Richard Stallman @ 2003-01-01 16:46 UTC (permalink / raw)
Cc: emacs-devel
I think that file-modes can return nil. (Ange-FTP always returns
nil.) Then the logand will fail.
So is it a bug in the current code (which should deal with a nil
return value of file-modes), or is it a bug in Ange-FTP (which
returns nil)?
It's a bug in my change. Thanks for reporting it--I will fix it.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2002-12-30 20:53 Change in backup-buffer: how to interpret? Kai Großjohann
2002-12-30 20:58 ` Kai Großjohann
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