bug#37095: [PATCH] Save match data in ucs-normalize-region

[Lars Ingebrigtsen]

Akinori MUSHA <knu@iDaemons.org> writes:

> A patch generated by git format-patch is attached below, which simply
> wraps `ucs-normalize-region` with `save-match-data`.
>
> I'm a user of the Emacs Mac port by mituharu was investigating a bug
> where dired fails to open a certain local directory on macOS.  The
> error was raised at `replace-match` in the `insert-directory`
> function:
>
> ```
>               (when (re-search-forward "^ *\\(total\\)" nil t)
>                 (let ((available (get-free-disk-space ".")))
>                   (when available
>                     ;; Replace "total" with "used", to avoid confusion.
>                     (replace-match "total used in directory" nil nil nil 1)
> ```
>
> And it turned out the match data changed after returning from
> `get-free-disk-space` and that was why `replace-match` failed.

You don't say what Emacs version you're reporting this bug for, but the
following patch was applied in February 2018 to the Emacs trunk, so I
think this problem has been fixed by now:

diff --git a/lisp/files.el b/lisp/files.el
index 91aa95d631..75d3b7b1e7 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -6473,9 +6473,10 @@ get-free-disk-space
 space (normally, the number of free 1KB blocks).
 
 If DIR's free space cannot be obtained, this function returns nil."
-  (let ((avail (nth 2 (file-system-info dir))))
-    (if avail
-       (format "%.0f" (/ avail 1024)))))
+  (save-match-data
+    (let ((avail (nth 2 (file-system-info dir))))
+      (if avail
+         (format "%.0f" (/ avail 1024))))))
 
 ;; The following expression replaces `dired-move-to-filename-regexp'.
 (defvar directory-listing-before-filename-regexp


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