(fill-context-prefix): Match the two prefixes

differently to avoid pathological exponential-time case.

diff --git a/lisp/textmodes/fill.el b/lisp/textmodes/fill.el
index 34fa1f544bba2746ddce01445b83dccfd50200dc..e4545021cc245edae82ac57f627d93a3072157ea 100644 (file)
--- a/lisp/textmodes/fill.el
+++ b/lisp/textmodes/fill.el
@@ -237,18 +237,14 @@ act as a paragraph-separator."
                ;; just use it (this subsumes the 2 previous checks).
                ;; Used when first line is `/* ...' and second-line is
                ;; ` * ...'.
-               (save-excursion
-                 (goto-char firstline)
-                 (looking-at
-                  (apply 'concat
-                         (mapcar (lambda (c)
-                                   (if (memq c '(?\t ?\ ))
-                                       ;; The number of chars might not
-                                       ;; match up if there's a mix of
-                                       ;; tabs and spaces.
-                                       "\\([ \t]*\\|.\\)"
-                                     (regexp-quote (string c))))
-                                 second-line-prefix))))
+               (string-match
+                (concat "\\`"
+                        (mapconcat
+                         (lambda (c) (regexp-quote (string c)))
+                         (replace-regexp-in-string "[ \t]+" "" first-line-prefix)
+                         "?")
+                        "?\\'")
+                (replace-regexp-in-string "[ \t]+" "" second-line-prefix))
                second-line-prefix
 
              ;; Use the longest common substring of both prefixes,