From 2f3b67c9e060366c9018efa96f6bd4f3aef0bf43 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Wed, 19 Mar 2014 14:13:47 +0100
Subject: [PATCH] nitpicker: Fix implementation of Mode interface

The generalization of nitpicker's graphic backend changed the interface
of 'Mode::forget', which is a (non-pure) virtual function implemented
by 'User_state::forget'. Unfortunately, the signature change was not
applied to 'User_state::forget' so that the actual implementation was
no longer called. This inconsistency remained unnoticed because there
is a default implementation of the virtual function.

The effect of the omission of the 'User_state::forget' call was a
dangling pointer ('User_state::_pointed_view').

Lesson learned: Always annotate functions with the C++11 'override' when
implementing virtual functions.
---
 os/src/server/nitpicker/mode.h        | 3 ++-
 os/src/server/nitpicker/user_state.cc | 2 +-
 os/src/server/nitpicker/user_state.h  | 2 +-
 os/src/server/nitpicker/view_stack.cc | 2 +-
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/os/src/server/nitpicker/mode.h b/os/src/server/nitpicker/mode.h
index 1b95fe56b..a6e645760 100644
--- a/os/src/server/nitpicker/mode.h
+++ b/os/src/server/nitpicker/mode.h
@@ -15,6 +15,7 @@
 #define _MODE_H_
 
 class View;
+class Canvas_base;
 
 class Mode
 {
@@ -53,7 +54,7 @@ class Mode
 		/**
 		 * Discard all references to specified view
 		 */
-		virtual void forget(View const &v) {
+		virtual void forget(Canvas_base &, View const &v) {
 			if (&v == _focused_view) _focused_view = 0; }
 };
 
diff --git a/os/src/server/nitpicker/user_state.cc b/os/src/server/nitpicker/user_state.cc
index 8b854a50b..7ee395c46 100644
--- a/os/src/server/nitpicker/user_state.cc
+++ b/os/src/server/nitpicker/user_state.cc
@@ -281,7 +281,7 @@ void User_state::handle_event(Input::Event ev, Canvas_base &canvas)
 void User_state::forget(Canvas_base &canvas, View const &view)
 {
 	if (focused_view() == &view) {
-		Mode::forget(view);
+		Mode::forget(canvas, view);
 		_menubar.state(Menubar_state(*this, "", "", BLACK));
 		update_all_views(canvas);
 	}
diff --git a/os/src/server/nitpicker/user_state.h b/os/src/server/nitpicker/user_state.h
index 4d9d38a32..5c412c319 100644
--- a/os/src/server/nitpicker/user_state.h
+++ b/os/src/server/nitpicker/user_state.h
@@ -89,7 +89,7 @@ class User_state : public Mode, public View_stack
 		/**
 		 * Mode interface
 		 */
-		void forget(Canvas_base &, View const &);
+		void forget(Canvas_base &, View const &) override;
 };
 
 #endif
diff --git a/os/src/server/nitpicker/view_stack.cc b/os/src/server/nitpicker/view_stack.cc
index a72e2343e..89230750a 100644
--- a/os/src/server/nitpicker/view_stack.cc
+++ b/os/src/server/nitpicker/view_stack.cc
@@ -315,7 +315,7 @@ void View_stack::remove_view(Canvas_base &canvas, View const &view, bool redraw)
 	 * the current one, resulting in a dangling pointer right after the view
 	 * gets destructed by the caller of 'removed_view'.
 	 */
-	_mode.forget(view);
+	_mode.forget(canvas, view);
 
 	/* redraw area where the view was visible */
 	if (redraw)