bug#81481: 31.0.91; dired-test-filename-with-newline failures on 32-bit Solaris sparc

On Mon, 27 Jul 2026 00:42:06 +0200 Stephen Berman <[email protected]> wrote:

> On Sun, 26 Jul 2026 10:45:53 -0700 Paul Eggert <[email protected]> wrote:
>
>> On 2026-07-26 02:17, Stephen Berman wrote:
>>
>>> files, if you visit the directory in Dired, move with `n' to the entry
>>> `a b' (so the cursor is on "a") and evaluate
>>> `(dired-move-to-end-of-filename)', where is point now?  I'd guess
>>> between "a" and the space.
>>
>> No, it's after the 'b'.
>>
>> However, it is indeed after the 'a' for the file name that is 'a' followed by
>> newline followed by 'b'.
>>
>>>If instead point is after "b" (as it is with> GNU `ls'), then I have no idea
>> why the search fails.
>>
>> Without looking at the Emacs code I can intuitively see why it works for 'a b'
>> but not for 'a' newline 'b'. In the former, there's no other way to interpret
>> the line. In the latter there is.
>
> Oops, I had blinders on before: when I looked at the test code after
> seeing your report I was only paying attention to the fact that
> searching backward for a string containing a space fails, but ignoring
> where point is when `search-backward' was called, namely, where
> `dired-move-to-end-of-filename' put it, which, on Solaris where `ls'
> lacks the --dired switch, is just before the newline in the filename, as
> you have just confirmed.  But in the test the part of the file name with
> the space is after the newline, so of course the search fails!
>
>>> If you run just `dired-test-filename-with-newline-1' on
>>> Solaris in a fresh Emacs session where Dired has not yet been used, I
>>> would expect you to see this message.
>>
>> Yes, I see the message "ls does not support --dired -N; see
>> `dired-use-ls-dired' for more details.". If I then visit a directory
>> containing an entry that has a newline a *Warnings* buffer appears that says
>> the following:
>>
>> Warning (dired): Literal newline in file name.
>> This Dired buffer displays a file name containing a literal newline character.
>> Executing Dired operations on files displayed this way may fail and signal an
>> error.  To avoid this you can temporarily change the display for all Dired
>> buffers, so that newlines in file names appear as "\n", by typing `M-:' and
>> entering `(setopt dired-auto-toggle-b-switch t)' in the minibuffer.  To change
>> the display only for this Dired buffer click or press RETURN `here'. See
>> `(emacs) Dired Enter' for other alternatives and more information.
>
> Right, this is because the test for whether a file name in a directory
> contains a newline uses the primitive function `directory-files'; how
> Dired (or `ls') displays file names plays no role in that test.
> However, displaying the warning also depends on Dired using an `ls' that
> supports the -b switch.  This condition was added in abde2d1ed3b due to
> a report of the same Dired tests failing as you have reported; but in
> that case, the `ls' used by Dired supported neither --dired nor -b, and
> I concluded that only testing for -b support was sufficient
> (https://debbugs.gnu.org/cgi/bugreport.cgi?bug=80499#190).  But your
> report shows that conclusion was mistaken.  Moreover, what the above
> warning says to do to avoid problems in Dired with a literal newline in
> a file name does not work on Solaris, since -b there does not do what -b
> in GNU `ls' does; so showing the warning in Solaris is not really
> appropriate.
>
>>> If so, then skipping the test on
>>> Solaris would be appropriate.
>
> I think this is correct, but I think the fix, both for the test failures
> and for deciding whether to display the warning and suggest changing the
> the Dired display, is to use `dired-use-ls-dired', as was considered
> earlier on in that other bug report
> (https://debbugs.gnu.org/cgi/bugreport.cgi?bug=80499#145), instead
> testing for ls support of -b.  I'll post a patch later.

The patch is attached.  If I made no mistake, the tests
dired-test-filename-with-newline-1 and
dired-test-filename-with-newline-2 should now be skipped on platforms
using an `ls' that does not support the --dired switch, and on such
platforms no warning should be displayed when visiting in Dired a
directory listing a file name containing a newline with
`dired-auto-toggle-b-switch' set to nil (the default), and setting this
user option to t should have no effect on such platforms.  Paul, can you
confirm for Solaris, and John Muhl (Cc'd), can you confirm for Alpine,
and Eli, can you confirm for MS-Windows?  (On platforms with an `ls'
that supports --dired, the behavior with the patch should be unchanged
from the behavior with the current code; I've confirmed this for my
GNU/Linux system.)

Eli, if you, Paul and John confirm as requested, can this patch go into
emacs-31?  The bug report of the test failures was against emacs-31, and
the the only substantive change is that where previously we tested
whether `ls' supports a -b switch, now with the patch we test whether
`ls' supports the --dired switch.

Steve Berman

diff --git a/lisp/dired.el b/lisp/dired.el
index 53ec6779061..237d4bbd69b 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -1492,7 +1492,10 @@ dired-internal-noselect
                 (dired-switches-escape-p dired-listing-switches)
                 (dired-switches-escape-p dired-actual-switches))
       (when (and (dired--filename-with-newline-p)
-                 (dired--ls-accept-b-switch-p))
+                 ;; Can't use `dired-use-ls-dired' because users could
+                 ;; set it to `t' even though their `ls' does not
+                 ;; support "--dired".
+                 (dired--check-use-ls-dired))
         (dired--display-filename-with-newline-warning buffer)))
     (set-buffer old-buf)
     buffer))
@@ -1782,6 +1785,10 @@ dired-switches-recursive-p
   "Return non-nil if the string SWITCHES contains -R or --recursive."
   (dired-check-switches switches "R" "recursive"))
 
+(defun dired--check-use-ls-dired ()
+  "Return non-nil if `ls' supports the \"--dired\" switch."
+  (eq 0 (call-process insert-directory-program nil nil nil "--dired" "-N")))
+
 (defun dired-insert-directory (dir switches &optional file-list wildcard hdr)
   "Insert a directory listing of DIR, Dired style.
 Use SWITCHES to make the listings.
@@ -1801,11 +1808,7 @@ dired-insert-directory
          (not (bound-and-true-p eshell-ls-use-in-dired))
 	 (or remotep
              (if (eq dired-use-ls-dired 'unspecified)
-		 ;; Check whether "ls --dired" gives exit code 0, and
-		 ;; save the answer in `dired-use-ls-dired'.
-		 (or (setq dired-use-ls-dired
-			   (eq 0 (call-process insert-directory-program
-                                               nil nil nil "--dired" "-N")))
+		 (or (setq dired-use-ls-dired (dired--check-use-ls-dired))
 		     (progn
 		       (message "ls does not support --dired -N; \
 see `dired-use-ls-dired' for more details.")
@@ -4066,10 +4069,6 @@ dired--filename-with-newline-p
 a literal newline or as \"\\n\")."
   (directory-files default-directory nil "\n"))
 
-(defun dired--ls-accept-b-switch-p ()
-  "Return non-nil if the `ls' used by Dired accepts the `b' switch."
-  (eq 0 (call-process insert-directory-program nil nil nil "-b")))
-
 (defun dired--remove-b-switch ()
   "Remove all variants of the `b' switch from `dired-actual-switches'.
 This removes not only all occurrences of the short form `-b' but also
@@ -4104,7 +4103,10 @@ dired--toggle-b-switch
 (defun dired--set-auto-toggle-b-switch (symbol value)
   "The :set function for user option `dired-auto-toggle-b-switch'."
   (custom-set-default symbol value)
-  (when (dired--ls-accept-b-switch-p)
+  (when
+      ;; Can't use `dired-use-ls-dired' because users could set it to
+      ;; `t' even though their `ls' does not support "--dired".
+      (dired--check-use-ls-dired)
     (if value
         (add-hook 'post-command-hook #'dired--toggle-b-switch nil t)
       (remove-hook 'post-command-hook #'dired--toggle-b-switch t))
diff --git a/test/lisp/dired-tests.el b/test/lisp/dired-tests.el
index 65ca58cc705..47ead6a30b3 100644
--- a/test/lisp/dired-tests.el
+++ b/test/lisp/dired-tests.el
@@ -660,10 +660,9 @@ dired-test-hide-absolute-location-disabled
 
 (ert-deftest dired-test-filename-with-newline-1 () ; bug#79528, bug#80499
   "Test handling of file name with literal embedded newline."
-  ;; File names with embedded newlines are not allowed on MS-Windows and
-  ;; MS-DOS.
-  (skip-when (memq system-type '(windows-nt ms-dos)))
-  (skip-unless (dired--ls-accept-b-switch-p))
+  ;; The handling of file names with embedded newlines requires an `ls'
+  ;; that supports the "--dired" switch.
+  (skip-unless (dired--check-use-ls-dired))
   (with-current-buffer "*Messages*"
     (let ((inhibit-read-only t))
       (erase-buffer)))
@@ -696,10 +695,9 @@ dired-test-filename-with-newline-1
 
 (ert-deftest dired-test-filename-with-newline-2 () ; bug#79528, bug#80499
   "Test handling of file name with embedded newline using `b' switch."
-  ;; File names with embedded newlines are not allowed on MS-Windows and
-  ;; MS-DOS.
-  (skip-when (memq system-type '(windows-nt ms-dos)))
-  (skip-unless (dired--ls-accept-b-switch-p))
+  ;; The handling of file names with embedded newlines requires an `ls'
+  ;; that supports the "--dired" switch.
+  (skip-unless (dired--check-use-ls-dired))
   (with-current-buffer "*Messages*"
     (let ((inhibit-read-only t))
       (erase-buffer)))