std::underlying_type is not supported by the g++ 4.6 used by CI server

src/modules/systemlib/mixer/mixer.h

@@ -447,7 +447,8 @@ private:
  *
  * Values are generated by the multi_tables script and placed to mixer_multirotor.generated.h
  */
-enum class MultirotorGeometry : unsigned int;
+using MultirotorGeometryUnderlyingType = unsigned int;
+enum class MultirotorGeometry : MultirotorGeometryUnderlyingType;
 
 /**
  * Multi-rotor mixer for pre-defined vehicle geometries.

src/modules/systemlib/mixer/mixer_multirotor.cpp

@@ -78,8 +78,6 @@ float constrain(float val, float min, float max)
 }
 }
 
-using GeometryType = typename std::underlying_type<MultirotorGeometry>::type;
-
 MultirotorMixer::MultirotorMixer(ControlCallback control_cb,
 				 uintptr_t cb_handle,
 				 MultirotorGeometry geometry,
@@ -92,8 +90,8 @@ MultirotorMixer::MultirotorMixer(ControlCallback control_cb,
 	_pitch_scale(pitch_scale),
 	_yaw_scale(yaw_scale),
 	_idle_speed(-1.0f + idle_speed * 2.0f),	/* shift to output range here to avoid runtime calculation */
-	_rotor_count(_config_rotor_count[(GeometryType)geometry]),
-	_rotors(_config_index[(GeometryType)geometry])
+	_rotor_count(_config_rotor_count[(MultirotorGeometryUnderlyingType)geometry]),
+	_rotors(_config_index[(MultirotorGeometryUnderlyingType)geometry])
 {
 }
 

src/modules/systemlib/mixer/multi_tables

@@ -151,7 +151,7 @@ tables = [quad_x, quad_plus, quad_v, quad_wide, hex_x, hex_plus, hex_cox, octa_x
 
 
 def printEnum():
-    print "enum class MultirotorGeometry : unsigned int {"
+    print "enum class MultirotorGeometry : MultirotorGeometryUnderlyingType {"
     for table in tables:
         print "\t{},".format(variableName(table).upper())