[pull] master from beyond-all-reason:master

rts/Sim/MoveTypes/GroundMoveType.cpp

@@ -3322,8 +3322,9 @@ bool CGroundMoveType::UpdateDirectControl()
 		ChangeSpeed(0.0f, false, true);
 	}
 
-	if (unitCon.left ) { ChangeHeading(owner->heading + turnRate); turnSign =  1.0f; }
-	if (unitCon.right) { ChangeHeading(owner->heading - turnRate); turnSign = -1.0f; }
+	const short unitTurnRate = FloatToHeading(turnRate);
+	if (unitCon.left ) { ChangeHeading(owner->heading + unitTurnRate); turnSign =  1.0f; }
+	if (unitCon.right) { ChangeHeading(owner->heading - unitTurnRate); turnSign = -1.0f; }
 
 	// local client is controlling us
 	if (selfCon.GetControllee() == owner)

rts/Sim/Path/IPathController.cpp

@@ -79,7 +79,8 @@ short GMTDefaultPathController::GetDeltaHeading(
 	// add lookahead term to avoid overshooting target heading
 	// note that turnBrakeDist is always positive
 	const short brakeDistFactor = (absTurnSpeed >= maxTurnAccel);
-	const short stopTurnHeading = oldHeading + (turnBrakeDist * Sign(curTurnSpeed) * brakeDistFactor);
+	const short brakeDist = FloatToHeading(turnBrakeDist * Sign(curTurnSpeed));
+	const short stopTurnHeading = oldHeading + (brakeDist * brakeDistFactor);
 	const short curDeltaHeading = newHeading - stopTurnHeading;
 
 	if (brakeDistFactor == 0) {

rts/System/SpringMath.h

@@ -52,6 +52,7 @@ short int GetHeadingFromFacing(const int facing) _pure _warn_unused_result;
 int GetFacingFromHeading(const short int heading) _pure _warn_unused_result;
 float GetHeadingFromVectorF(const float dx, const float dz) _pure _warn_unused_result;
 short int GetHeadingFromVector(const float dx, const float dz) _pure _warn_unused_result;
+short int FloatToHeading(const float angle) _pure _warn_unused_result;
 shortint2 GetHAndPFromVector(const float3 vec) _pure _warn_unused_result; // vec should be normalized
 float2 GetHAndPFromVectorF(const float3 vec) _pure _warn_unused_result; // vec should be normalized
 float3 GetVectorFromHeading(const short int heading) _pure _warn_unused_result;

rts/System/SpringMath.inl

@@ -22,6 +22,17 @@ inline short int GetHeadingFromFacing(const int facing)
 	}
 }
 
+// headings are circular 16-bit integer angles, so sums of them are meant to wrap.
+// float->short is UB once out of range, so the float side has to be in range
+// already; the assert catches a caller that is not in debug builds.
+inline short int FloatToHeading(const float angle)
+{
+	assert(angle >= static_cast<float>(std::numeric_limits<short int>::min())
+		&& angle <= static_cast<float>(std::numeric_limits<short int>::max()));
+
+	return static_cast<short int>(angle);
+}
+
 inline int GetFacingFromHeading(const short int heading)
 {
 	if (heading >= 0) {