bug#21808: 24.3; tramp sorting with regular expression crashes whole dir listing

[Piotr Wasik <piotr.wasik@gmail.com>]

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hi,

I try to set up tramp with adb to access nexus. Its root directory contains
a protected file called factory and directory listing returns: "lstat
'//factory' failed: Permission denied" as one of files.

it crashes with the following backtrace
;; Debugger entered--Lisp error: (args-out-of-range "lstat '//factory'
failed: Permission denied" 55 43)
;;   tramp-adb-ls-output-name-less-p("lstat '//factory' failed: Permission
denied" "lrwxrwxrwx root     root            0 2015-11-01 13:49 etc ->
/system/etc")
;;   sort(("drwxr-xr-x root     root            0 2015-11-01 13:49 acct"
"drwxrwx--- system   cache           0 2015-11-01 15:03 cache" "lrwxrwxrwx
root     root            0 1970-01-01 01:00 charger -> /sbin/healthd"
"dr-x------ root     root            0 2015-11-01 13:49 config" "lrwxrwxrwx
root     root            0 2015-11-01 13:49 d -> /sys/kernel/debug")
tramp-adb-ls-output-name-less-p)
;;   tramp-adb-sh-fix-ls-output()
;;   tramp-adb-handle-directory-files-and-attributes("/adb::/")
;;   eval((tramp-adb-handle-directory-files-and-attributes "/adb::/") nil)
;;   eval-last-sexp-1(t)
;;   eval-last-sexp(t)
;;   eval-print-last-sexp()
;;   call-interactively(eval-print-last-sexp nil nil)

I suggest a fix:

(defun tramp-adb-ls-output-name-less-p (a b)
  "Sort \"ls\" output by name, ascending."
  (let (posa posb matched-a matched-b)
    (setq matched-a (string-match dired-move-to-filename-regexp a))
    (setq posa (match-end 0))
    (setq matched-b (string-match dired-move-to-filename-regexp b))
    (setq posb (match-end 0))
    (string-lessp (substring a (if matched-a a 0)) (substring b (if
matched-b b 0)))))

I added matched-a and matched-b variables so even if directory listing
returns something unexpected, sorting completes normally.

Cheers,
Piotr

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