Re: C-g while exiting the minibuffer

[martin rudalics]

> Now I wonder what should be the best way to fix this.  I can just switch
> the above two code blocks, which will fix the immediate problem (a C-g
> will not prevent canceling the frame-focus redirected), but I think this
> points to a larger problem of hitting C-g while processing unwind forms.
> Of course binding inhibit-quit during processing of unwind forms could
> be a source of problem in itself (if those forms fail to terminate).

I still have hare/tortoise implementations of Fset_window_prev_buffers
and Fset_window_next_buffers (for pure curiosity I attach the
corresponding part of a larger patch here).  Chong didn't want to
install them then because he considered it overengineering.  Installing
them means select_window could safely modify these lists with quitting
inhibited.

Calling `buffer-list-update-hook' would have to be deferred until the
end of `set-window-configuration' - no great deal IMHO.

Do you see any more problems?

martin

=== modified file 'src/window.c'
--- src/window.c        2012-02-23 17:40:33 +0000
+++ src/window.c        2012-02-27 07:43:06 +0000
@@ -51,7 +51,7 @@
 #endif
 
 Lisp_Object Qwindowp, Qwindow_live_p;
-static Lisp_Object Qwindow_configuration_p, Qrecord_window_buffer;
+static Lisp_Object Qwindow_configuration_p;
 static Lisp_Object Qwindow_deletable_p, Qdelete_window, Qdisplay_buffer;
 static Lisp_Object Qreplace_buffer_in_windows, Qget_mru_window;
 static Lisp_Object Qwindow_resize_root_window, 
Qwindow_resize_root_window_vertically;
@@ -1647,15 +1647,41 @@
 
 DEFUN ("set-window-prev-buffers", Fset_window_prev_buffers,
        Sset_window_prev_buffers, 2, 2, 0,
-       doc: /* Set WINDOW's previous buffers to PREV-BUFFERS.
+       doc:         /* Set WINDOW's previous buffers to PREV-BUFFERS.
 WINDOW must be a live window and defaults to the selected one.
 
 PREV-BUFFERS should be a list of elements (BUFFER WINDOW-START POS),
 where BUFFER is a buffer, WINDOW-START is the start position of the
 window for that buffer, and POS is a window-specific point value.  */)
-     (Lisp_Object window, Lisp_Object prev_buffers)
+  (Lisp_Object window, Lisp_Object prev_buffers)
 {
-  return decode_window (window)->prev_buffers = prev_buffers;
+  register struct window *w = decode_window (window);
+
+  if (NILP (prev_buffers))
+    return w->prev_buffers = Qnil;
+  else if (!CONSP (prev_buffers))
+    return w->prev_buffers;
+  else
+    {
+      /* Run cycle detection on prev_buffers.  */
+      Lisp_Object tortoise, hare;
+
+      hare = tortoise = prev_buffers;
+      while (CONSP (hare))
+       {
+         hare = XCDR (hare);
+         if (!CONSP (hare))
+           break;
+
+         hare = XCDR (hare);
+         tortoise = XCDR (tortoise);
+
+         if (EQ (hare, tortoise))
+           return w->prev_buffers;
+       }
+
+      return w->prev_buffers = prev_buffers;
+    }
 }
 
 DEFUN ("window-next-buffers", Fwindow_next_buffers, Swindow_next_buffers,
@@ -1674,7 +1700,33 @@
 NEXT-BUFFERS should be a list of buffers.  */)
      (Lisp_Object window, Lisp_Object next_buffers)
 {
-  return decode_window (window)->next_buffers = next_buffers;
+  register struct window *w = decode_window (window);
+
+  if (NILP (next_buffers))
+    return w->next_buffers = Qnil;
+  else if (!CONSP (next_buffers))
+    return w->next_buffers;
+  else
+    {
+      /* Run cycle detection on next_buffers.  */
+      Lisp_Object tortoise, hare;
+
+      hare = tortoise = next_buffers;
+      while (CONSP (hare))
+       {
+         hare = XCDR (hare);
+         if (!CONSP (hare))
+           break;
+
+         hare = XCDR (hare);
+         tortoise = XCDR (tortoise);
+
+         if (EQ (hare, tortoise))
+           return w->next_buffers;
+       }
+
+      return w->next_buffers = next_buffers;
+    }
 }