probably safer: ConvertValue

stepmania/src/LightsManager.cpp

@@ -426,7 +426,7 @@ void LightsManager::ChangeTestCabinetLight( int iDir )
 	m_iControllerTestManualCycleCurrent = -1;
 
 	m_clTestManualCycleCurrent = (CabinetLight)(m_clTestManualCycleCurrent+iDir);
-	wrap( UnionCast(m_clTestManualCycleCurrent), NUM_CabinetLight );
+	wrap( *ConvertValue<int>(&m_clTestManualCycleCurrent), NUM_CabinetLight );
 }
 
 void LightsManager::ChangeTestGameButtonLight( int iDir )

stepmania/src/Profile.cpp

@@ -1161,7 +1161,7 @@ void Profile::LoadGeneralDataFromNode( const XNode* pNode )
 	pNode->GetChildValue( "TotalGameplaySeconds",			m_iTotalGameplaySeconds );
 	pNode->GetChildValue( "CurrentCombo",				m_iCurrentCombo );
 	pNode->GetChildValue( "TotalCaloriesBurned",			m_fTotalCaloriesBurned );
-	pNode->GetChildValue( "GoalType",				UnionCast(m_GoalType) );
+	pNode->GetChildValue( "GoalType",				*ConvertValue<int>(&m_GoalType) );
 	pNode->GetChildValue( "GoalCalories",				m_iGoalCalories );
 	pNode->GetChildValue( "GoalSeconds",				m_iGoalSeconds );
 	pNode->GetChildValue( "LastPlayedMachineGuid",			m_sLastPlayedMachineGuid );

stepmania/src/RageUtil.h

@@ -135,6 +135,40 @@ int &UnionCast( T &e )
         return CastSimilarTypes<int,T>(e);
 }
 
+/* Helper for ConvertValue(). */
+template<typename TO, typename FROM>
+struct ConvertValueHelper
+{
+	explicit ConvertValueHelper( FROM *pVal ): m_pFromValue(pVal)
+	{
+		m_ToValue = static_cast<TO>( *m_pFromValue );
+	}
+
+	~ConvertValueHelper()
+	{
+		*m_pFromValue = static_cast<FROM>( m_ToValue );
+	}
+
+	TO &operator *() { return m_ToValue; }
+	operator TO *() { return &m_ToValue; }
+
+private:
+	FROM *m_pFromValue;
+	TO m_ToValue;
+};
+
+/*
+ * Safely temporarily convert between types.  For example,
+ *
+ * float f = 10.5;
+ * *ConvertValue<int>(&f) = 12;
+ */
+template<typename TO, typename FROM>
+ConvertValueHelper<TO, FROM> ConvertValue( FROM *pValue )
+{
+	return ConvertValueHelper<TO, FROM>( pValue );
+}
+
 /*
  * Safely add an integer to an enum.
  *
@@ -154,7 +188,7 @@ int &UnionCast( T &e )
 template<typename T>
 static inline void enum_add( T &val, int iAmt )
 {
-	UnionCast( val ) += iAmt;
+	*ConvertValue<int>(&val) += iAmt;
 }
 
 template<typename T>

stepmania/src/ScreenTextEntry.cpp

@@ -406,7 +406,7 @@ void ScreenTextEntryVisual::MoveY( int iDir )
 	do
 	{
 		m_iFocusY = enum_add2( m_iFocusY,  +iDir );
-		wrap( UnionCast(m_iFocusY), NUM_KeyboardRow );
+		wrap( *ConvertValue<int>(&m_iFocusY), NUM_KeyboardRow );
 
 		// HACK: Round to nearest option so that we always stop 
 		// on KEYBOARD_ROW_SPECIAL.