1 files changed, 38 insertions, 3 deletions

diff --git a/lisp/progmodes/compile.el b/lisp/progmodes/compile.el
index 9114266570e..53237cafb13 100644
--- a/lisp/progmodes/compile.el
+++ b/lisp/progmodes/compile.el
@@ -553,10 +553,28 @@ While grep runs asynchronously, you can use the \\[next-error] command
 to find the text that grep hits refer to.
 
 This command uses a special history list for its arguments, so you can
-easily repeat a grep command."
+easily repeat a grep command.
+
+A prefix argument says to default the argument based upon the current
+tag the cursor is over."
   (interactive
-   (list (read-from-minibuffer "Run grep (like this): "
-                               grep-command nil nil 'grep-history)))
+   (let (grep-default)
+     (when (and current-prefix-arg grep-history)
+       (let* ((tag-default
+               (funcall (or find-tag-default-function
+                            (get major-mode 'find-tag-default-function)
+                            ;; We use grep-tag-default instead of
+                            ;; find-tag-default, to avoid loading etags.
+                            'grep-tag-default))))
+         (setq grep-default (car grep-history))
+         ;; Replace the thing matching for with that around cursor
+         (if (string-match "[^ ]+\\s +\\(-[^ ]+\\)*\\s *\\(\"[^\"]+\"\\|[^ ]+\\)" grep-default)
+             (setq grep-default (replace-match tag-default t t
+                                               grep-default 2)))))
+     (list (read-from-minibuffer "Run grep (like this): "
+                                 (or grep-default grep-command)
+                                 nil nil 'grep-history))))
+
   ;; Setting process-setup-function makes exit-message-function work
   ;; even when async processes aren't supported.
   (let* ((compilation-process-setup-function 'grep-process-setup)
@@ -567,6 +585,23 @@ easily repeat a grep command."
                                 ;; Give it a simpler regexp to match.
                                 nil grep-regexp-alist)))))
 
+;; This is a copy of find-tag-default from etags.el.
+(defun grep-tag-default ()
+  (save-excursion
+    (while (looking-at "\\sw\\|\\s_")
+      (forward-char 1))
+    (when (or (re-search-backward "\\sw\\|\\s_"
+                                  (save-excursion (beginning-of-line) (point))
+                                  t)
+              (re-search-forward "\\(\\sw\\|\\s_\\)+"
+                                 (save-excursion (end-of-line) (point))
+                                 t))
+      (goto-char (match-end 0))
+      (buffer-substring (point)
+                        (progn (forward-sexp -1)
+                               (while (looking-at "\\s'")
+                                 (forward-char 1))
+                               (point))))))
 
 ;;;###autoload
 (defun grep-find (command-args)