bug#45540: 27.1; symbolic links crash dired

bug#45540: 27.1; symbolic links crash dired

[Devon Sean McCullough]

Here's a fix.  I did NOT check this carefully.
Dired crashes when (< (length file-name) (length root))

diff -aBbdu --label 
/Applications/Emacs-27.1.app/Contents/Resources/lisp/files.el.gz --label 
\#\<buffer\ files.el.gz\> 
/var/folders/jv/9lctn91j0xqfv3f2kxc1lxx80000gn/T/jka-comtv7p5N 
/var/folders/jv/9lctn91j0xqfv3f2kxc1lxx80000gn/T/buffer-content-fatCkh
--- /Applications/Emacs-27.1.app/Contents/Resources/lisp/files.el.gz
+++ #<buffer files.el.gz>
@@ -4019,10 +4019,9 @@
    (let* ((file-name (or (buffer-file-name)
  			;; Handle non-file buffers, too.
  			(expand-file-name default-directory)))
-	 (sub-file-name (if (and file-name
+	 (sub-file-name (when (and file-name
                                   (file-name-absolute-p file-name))
-                            ;; FIXME: Why not use file-relative-name?
-			    (substring file-name (length root)))))
+			  (file-relative-name file-name root))))
      (condition-case err
          (dolist (entry class-variables variables)
            (let ((key (car entry)))

Diff finished.  Tue Dec 29 16:42:36 2020

bug#45540: 27.1; symbolic links crash dired

[Lars Ingebrigtsen]

Devon Sean McCullough <Emacs-hacker2018@jovi.net> writes:

> Here's a fix.  I did NOT check this carefully.
> Dired crashes when (< (length file-name) (length root))

The patch looks reasonable -- but do you have a test case that
reproduces this bug (starting from "emacs -Q") so that we can verify the
bug and the fix?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#45540: 27.1; symbolic links crash dired

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Devon Sean McCullough <Emacs-hacker2018@jovi.net> writes:
>
>> Here's a fix.  I did NOT check this carefully.
>> Dired crashes when (< (length file-name) (length root))
>
> The patch looks reasonable -- but do you have a test case that
> reproduces this bug (starting from "emacs -Q") so that we can verify the
> bug and the fix?

I tried various link scenarios to come up with a case where file-name
was shorter than root, and I was unable to.  Do you have a test case for
such a setup?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#45540: 27.1; symbolic links crash dired

[Lars Ingebrigtsen]

(Please keep the debbugs address in the CC header; otherwise the mail
won't reach the bug tracker.)

Devon Sean McCullough <Emacs-hacker2018@jovi.net> writes:

> Before I patched it, dired was constantly crashing.
> I've unpatched it and (setq directory-abbrev-alist nil)
> but still no crash, mystery.  I'll keep digging.

Thanks.

bug#45540: 27.1; symbolic links crash dired

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> I tried various link scenarios to come up with a case where file-name
> was shorter than root, and I was unable to.  Do you have a test case for
> such a setup?

More information was requested, but no response was given within a
month, so I'm closing this bug report.  If the problem still exists,
please respond to this email and we'll reopen the bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no