From af7ef732bd497dd664b3cc97f9f1723545627593 Mon Sep 17 00:00:00 2001
From: Mark de Wever <koraq@xs4all.nl>
Date: Sat, 15 Oct 2011 18:06:24 +0000
Subject: [PATCH] Harden unit_movement_resetter class.

Add a warning regarding its usage and test whether the unit exists
before assigning to it. (Still a bit experimental, but initial tests
show no regressions.)
---
 src/unit.cpp |  8 ++++++++
 src/unit.hpp | 10 +++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/unit.cpp b/src/unit.cpp
index 73ebfaab401..af07a157299 100644
--- a/src/unit.cpp
+++ b/src/unit.cpp
@@ -2799,6 +2799,14 @@ unit_movement_resetter::unit_movement_resetter(unit &u, bool operate) :
 
 unit_movement_resetter::~unit_movement_resetter()
 {
+	assert(resources::units);
+
+	/*
+	 * This assert should be safe, but not 100% sure so if it fails need
+	 * some extra validation code in this function.
+	 */
+	assert(resources::units->has_unit(&u_));
+
 	u_.movement_ = moves_;
 }
 
diff --git a/src/unit.hpp b/src/unit.hpp
index c295399a2ec..81de17f2cc8 100644
--- a/src/unit.hpp
+++ b/src/unit.hpp
@@ -467,8 +467,16 @@ private:
 	void clear_visibility_cache() const { invisibility_cache_.clear(); }
 };
 
-/** Object which temporarily resets a unit's movement */
+/**
+ * Object which temporarily resets a unit's movement.
+ *
+ * @warning
+ * The unit whose movement is reset may not be deleted while a
+ * @ref unit_movement_resetter object 'holds'. So best use it only in a small
+ * scope.
+ */
 struct unit_movement_resetter
+	: private boost::noncopyable
 {
 	unit_movement_resetter(unit& u, bool operate=true);
 	~unit_movement_resetter();