bug#35448: 26.2; save-buffer silently fails in winNT if buffer name has forbidden chars

bug#35448: 26.2; save-buffer silently fails in winNT if buffer name has forbidden chars

[Tino Calancha]

emacs -Q
;; Do the following recipe in an empty directory

C-x b  schrodinger:cat RET
Miauuuu!!!
C-x C-s RET
;; A message in the minibuffer confirms the name of the file writen to disk.
;; Apparentely, the base name of such a file matches the buffer name.
M-: (file-exists-p buffer-file-name)
=> t
M-: (string= (file-name-nondirectory buffer-file-name) (buffer-name))
=> t


;; In fact, no file matches the buffer name in the directory
M-: (directory-files default-directory nil (buffer-name))
=> nil

;; There is an _empty_ file with name, the buffer name upto the colon
M-: (directory-files default-directory nil "schrod")
=> ("schrodinger")

M-: (with-temp-buffer
      (insert-file-contents "schrodinger")
      (buffer-size))
=> 0

--8<-----------------------------cut here---------------start------------->8---
diff --git a/lisp/files.el b/lisp/files.el
index c05d70a00e..93600d2edb 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -5106,6 +5106,9 @@ basic-save-buffer
                          (expand-file-name
                           (read-file-name "File to save in: "
                                           nil (expand-file-name (buffer-name))))))
+                    (when (and (eq 'windows-nt system-type)
+                               (string-match-p "[:*?\"<>]" (file-name-nondirectory filename)))
+                      (error "A file name cannot contain any of the following characters: :*?\"<>"))
                     (if (file-exists-p filename)
                         (if (file-directory-p filename)
                             ;; Signal an error if the user specified the name of an

--8<-----------------------------cut here---------------end--------------->8---


In GNU Emacs 26.2 (build 1, x86_64-w64-mingw32)
 of 2019-04-13 built on CIRROCUMULUS
Repository revision: fd1b34bfba8f3f6298df47c8e10b61530426f749
Windowing system distributor 'Microsoft Corp.', version 10.0.17763
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS THREADS LCMS2

Important settings:
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  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
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emacs)

Memory information:
((conses 16 97250 8162)
 (symbols 48 20206 1)
 (miscs 40 40 94)
 (strings 32 29729 1209)
 (string-bytes 1 773709)
 (vectors 16 14066)
 (vector-slots 8 496277 12810)
 (floats 8 51 284)
 (intervals 56 250 17)
 (buffers 992 11))

bug#35448: 26.2; save-buffer silently fails in winNT if buffer name has forbidden chars

[Eli Zaretskii]

> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Sat, 27 Apr 2019 18:36:14 +0900
> 
> 
> emacs -Q
> ;; Do the following recipe in an empty directory
> 
> C-x b  schrodinger:cat RET
> Miauuuu!!!
> C-x C-s RET
> ;; A message in the minibuffer confirms the name of the file writen to disk.
> ;; Apparentely, the base name of such a file matches the buffer name.
> M-: (file-exists-p buffer-file-name)
> => t
> M-: (string= (file-name-nondirectory buffer-file-name) (buffer-name))
> => t
> 
> 
> ;; In fact, no file matches the buffer name in the directory
> M-: (directory-files default-directory nil (buffer-name))
> => nil
> 
> ;; There is an _empty_ file with name, the buffer name upto the colon
> M-: (directory-files default-directory nil "schrod")
> => ("schrodinger")

It's a feature.  See

  https://en.wikipedia.org/wiki/NTFS#Alternate_data_streams_(ADS)
  http://www.flexhex.com/docs/articles/alternate-streams.phtml

Whether we should allow this in Emacs is a different matter, but this
was supported since day one, FWIW.

bug#35448: 26.2; save-buffer silently fails in winNT if buffer name has forbidden chars

[Eli Zaretskii]

> Date: Sat, 27 Apr 2019 13:05:05 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 35448@debbugs.gnu.org
> 
> > M-: (directory-files default-directory nil "schrod")
> > => ("schrodinger")
> 
> It's a feature.  See
> 
>   https://en.wikipedia.org/wiki/NTFS#Alternate_data_streams_(ADS)
>   http://www.flexhex.com/docs/articles/alternate-streams.phtml

And to see that your cat's meow is not lost, try this:

  C-u M-! streams schrodinger RET

bug#35448: 26.2; save-buffer silently fails in winNT if buffer name has forbidden chars

[Eli Zaretskii]

> Date: Sat, 27 Apr 2019 14:14:35 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 35448@debbugs.gnu.org
> 
> >   https://en.wikipedia.org/wiki/NTFS#Alternate_data_streams_(ADS)
> >   http://www.flexhex.com/docs/articles/alternate-streams.phtml
> 
> And to see that your cat's meow is not lost, try this:
> 
>   C-u M-! streams schrodinger RET

Even better, kill the buffer and then "C-x C-f schrodinger:cat RET".
(A program such as 'cat' will also show the text.)

bug#35448: 26.2; save-buffer silently fails in winNT if buffer name has forbidden chars

[Tino Calancha]

Eli Zaretskii <eliz@gnu.org> writes:

I saw the cat meow.
Since this is a feature I wasn't aware of, not a bug, then I am closing this bug.
>> >   https://en.wikipedia.org/wiki/NTFS#Alternate_data_streams_(ADS)
>> >   http://www.flexhex.com/docs/articles/alternate-streams.phtml
>> 
>> And to see that your cat's meow is not lost, try this:
>> 
>>   C-u M-! streams schrodinger RET
>
> Even better, kill the buffer and then "C-x C-f schrodinger:cat RET".
> (A program such as 'cat' will also show the text.)