(regexp-opt-group): Sort the strings when extracting a suffix.

diff --git a/lisp/emacs-lisp/regexp-opt.el b/lisp/emacs-lisp/regexp-opt.el
index de36f1d5446927614965cd90156b9837d2a0ae84..e849cd60b96095c70ff3a190bd33df677e32fef7 100644 (file)
--- a/lisp/emacs-lisp/regexp-opt.el
+++ b/lisp/emacs-lisp/regexp-opt.el
@@ -205,7 +205,10 @@ so we can use character sets rather than grouping parenthesis."
            (if (> (length xiffus) 0)
                ;; common suffix: take it and recurse on the prefixes.
                (let* ((n (- (length xiffus)))
-                      (prefixes (mapcar (lambda (s) (substring s 0 n)) strings)))
+                      (prefixes
+                       ;; Sorting is necessary in cases such as ("ad" "d").
+                       (sort (mapcar (lambda (s) (substring s 0 n)) strings)
+                             'string-lessp)))
                  (concat open-group
                          (regexp-opt-group prefixes t t)
                          (regexp-quote