Subject: Re: bug#10906: 24.0.94; `c-mark-function' does set the mark well

From: Alan Mackenzie <[email-masked]>
Date: Mon, 5 Mar 2012 18:41:33 +0000

Hello, Dani.

On Fri, Mar 02, 2012 at 12:03:48AM +0100, Dani Moncayo wrote:

> >> > Regarding bug#10906, I think `c-mark-function' should be rewritten
> >> > to follow the logic of `mark-defun'.

> > Any chance of a quick summary of how c-mark-function differs from
> > mark-defun?

> AFAIK, they differ at least in two things:

> 1. `mark-defun' saves the original point location in the mark ring,
> whereas `c-mark-function' does not.  IMO, the point should be saved,
> because in large defuns it may jump to a remote location and you may
> want to return back to the original position.  This bug report is
> about this inconsistency, as you can see in the original post.

> 2. Successive interactive invocations of `mark-defun' extend the
> region to the next defuns (which I find useful), whereas
> `c-mark-function' does not have this feature.  Bug #5525 is a request
> to remove this inconsistency, as you can see in the corresponding
> thread.

> >> Agreed, and BTW, if `c-mark-function' is going to be revised, please,
> >> take also this problem into account:

> >> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=5525

Here is a patch which should fix these problems.  The logic around
transient-mark-mode is somewhat complicated, so I would be grateful if
you would check the patch does the Right Thing.  I haven't amended the
doc string yet.  Thanks!

diff -r f6961b0b1c51 cc-cmds.el
--- a/cc-cmds.el	Fri Mar 02 21:25:40 2012 +0000
+++ b/cc-cmds.el	Mon Mar 05 18:35:18 2012 +0000
@@ -1966,8 +1966,20 @@
 
     (if (not decl-limits)
 	(error "Cannot find any declaration")
-      (goto-char (car decl-limits))
-      (push-mark (cdr decl-limits) nil t))))
+      (let* ((extend-region-p
+	      (or (and (eq this-command 'c-mark-function)
+		       (eq last-command 'c-mark-function))))
+	     (push-mark-p (and (eq this-command 'c-mark-function)
+			       (not extend-region-p)
+			       (not (and transient-mark-mode mark-active)))))
+	(if push-mark-p (push-mark (point)))
+	(if extend-region-p
+	    (progn
+	      (exchange-point-and-mark)
+	      (goto-char (cdr (c-declaration-limits t)))
+	      (exchange-point-and-mark))
+	  (goto-char (car decl-limits))
+	  (push-mark (cdr decl-limits) nil t))))))
 
 (defun c-cpp-define-name ()
   "Return the name of the current CPP macro, or NIL if we're not in one."

> -- 
> Dani Moncayo

-- 
Alan Mackenzie (Nuremberg, Germany).