Subject: 26.2; save-buffer silently fails in winNT if buffer name has forbidden chars

From: Tino Calancha <[email-masked]>
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")

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
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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)
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 (buffers 992 11))