Gtk+ memory management

[Andrey Maklakov <anmaklakov gmail com>]

 Hello.
    Can you help me and answer some questions about memory management in Gtk+?

Look at next function:

  1 void
  2 tbar_makemenu (gint button)
  3 {
  4   const gchar *sid;
  5   GList *list = NULL;
  6
  7   tbar_widget.menu[button] = gtk_menu_new ();
  8   if (button == SID)
  9       fdir_getext (filesdir, &list);
....
 15   g_list_foreach (list, (GFunc) &list_menu_additem, &button);
 16   g_list_free_full (list, &g_free);
 17   gtk_widget_show_all (tbar_widget.menu[button]);
 18   gtk_menu_tool_button_set_menu (GTK_MENU_TOOL_BUTTON
(tbar_widget.button[button]), tbar_widget.menu[button]);
 19 }

  My questions:
1) line 7 creates new GtkMenu, its child of GInitiallyUnowned, so
refcount = 1, but it is floating reference. True?
2) line 18 reference this menu with GtkMenuToolButton, so refcount =
1, and it is now not floating. True?
3) When I call this function 2nd time, and reference toolbutton with
new menu in line 18, what will happen? Old menu will get refcount = 0
and will be destroyed, or it is memory leak?
4) Will be destroyed menu items of old menu (which created in call of
g_list_foreach on line 15)?