(make-auto-save-file-name): Convert slashes to \! and double the backslashes.

1 files changed, 20 insertions, 7 deletions

diff --git a/lisp/files.el b/lisp/files.el
index b0aabd9eebf..b46b2294d05 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1950,14 +1950,27 @@ See also `auto-save-file-name-p'."
               "#"
               (file-name-nondirectory buffer-file-name)
               "#")
-    ;; For non-file bfr, use bfr name and Emacs pid.
-    ;; Don't allow slashes, though; auto-save would try to interpret it
-    ;; as a pathname, and it might not exist.
+
+    ;; Deal with buffers that don't have any associated files.  (Mail
+    ;; mode tends to create a good number of these.)
+
     (let ((buffer-name (buffer-name))
-          (save-match-data (match-data)))
-      (while (string-match "/" buffer-name)
-        (aset buffer-name (match-beginning 0) ?-))
-      (store-match-data save-match-data)
+          (limit 0))
+      ;; Use technique from Sebastian Kremer's auto-save
+      ;; package to turn slashes into \\!.  This ensures that
+      ;; the auto-save buffer name is unique.
+
+      (while (string-match "[/\\]" buffer-name limit)
+        (setq buffer-name (concat (substring buffer-name 0 (match-beginning 0))
+                        (if (string= (substring buffer-name
+                                                (match-beginning 0)
+                                                (match-end 0))
+                                     "/")
+                            "\\!"
+                          "\\\\")
+                        (substring buffer-name (match-end 0))))
+        (setq limit (1+ (match-end 0))))
+
       (expand-file-name (format "#%s#%s#" buffer-name (make-temp-name ""))))))
 
 (defun auto-save-file-name-p (filename)