waf: make implicit fallthroughs fatal

ArduCopter/mode_althold.cpp

@@ -55,7 +55,7 @@ void ModeAltHold::run()
 
     case AltHold_Landed_Ground_Idle:
         attitude_control->set_yaw_target_to_current_heading();
-        // FALLTHROUGH
+        FALLTHROUGH;
 
     case AltHold_Landed_Pre_Takeoff:
         attitude_control->reset_rate_controller_I_terms();

ArduCopter/mode_flowhold.cpp

@@ -283,7 +283,7 @@ void ModeFlowHold::run()
 
     case AltHold_Landed_Ground_Idle:
         attitude_control->set_yaw_target_to_current_heading();
-        // FALLTHROUGH
+        FALLTHROUGH;
 
     case AltHold_Landed_Pre_Takeoff:
         attitude_control->reset_rate_controller_I_terms();

ArduCopter/mode_loiter.cpp

@@ -151,7 +151,7 @@ void ModeLoiter::run()
 
     case AltHold_Landed_Ground_Idle:
         attitude_control->set_yaw_target_to_current_heading();
-        // FALLTHROUGH
+        FALLTHROUGH;
 
     case AltHold_Landed_Pre_Takeoff:
         attitude_control->reset_rate_controller_I_terms();

ArduCopter/mode_poshold.cpp

@@ -150,7 +150,7 @@ void ModePosHold::run()
         loiter_nav->init_target();
         loiter_nav->update();
         attitude_control->set_yaw_target_to_current_heading();
-        // FALLTHROUGH
+        FALLTHROUGH;
 
     case AltHold_Landed_Pre_Takeoff:
         attitude_control->reset_rate_controller_I_terms();

ArduCopter/mode_sport.cpp

@@ -103,7 +103,7 @@ void ModeSport::run()
 
     case AltHold_Landed_Ground_Idle:
         attitude_control->set_yaw_target_to_current_heading();
-        // FALLTHROUGH
+        FALLTHROUGH;
 
     case AltHold_Landed_Pre_Takeoff:
         attitude_control->reset_rate_controller_I_terms();

ArduCopter/mode_stabilize_heli.cpp

@@ -65,6 +65,7 @@ void ModeStabilize_Heli::run()
         if (!motors->limit.throttle_lower) {
             set_land_complete(false);
         }
+        break;
     case AP_Motors::SpoolState::SPOOLING_UP:
     case AP_Motors::SpoolState::SPOOLING_DOWN:
         // do nothing

Tools/ardupilotwaf/boards.py

@@ -94,6 +94,11 @@ def configure(self, cfg):
             cfg.srcnode.find_dir('libraries/AP_Common/missing').abspath()
         ])
 
+    def cc_version_gte(self, cfg, want_major, want_minor):
+        (major, minor, patchlevel) = cfg.env.CC_VERSION
+        return (int(major) > want_major or
+                (int(major) == want_major and int(minor) >= want_minor))
+
     def configure_env(self, cfg, env):
         # Use a dictionary instead of the convetional list for definitions to
         # make easy to override them. Convert back to list before consumption.
@@ -140,11 +145,16 @@ def configure_env(self, cfg, env):
                 '-Wno-inconsistent-missing-override',
                 '-Wno-mismatched-tags',
                 '-Wno-gnu-variable-sized-type-not-at-end',
+                '-Werror=implicit-fallthrough',
             ]
         else:
             env.CFLAGS += [
                 '-Wno-format-contains-nul',
             ]
+            if self.cc_version_gte(cfg, 7, 4):
+                env.CXXFLAGS += [
+                    '-Werror=implicit-fallthrough',
+                ]
 
         if cfg.env.DEBUG:
             env.CFLAGS += [
@@ -227,17 +237,21 @@ def configure_env(self, cfg, env):
                 '-Wno-gnu-designator',
                 '-Wno-mismatched-tags',
                 '-Wno-gnu-variable-sized-type-not-at-end',
+                '-Werror=implicit-fallthrough',
             ]
         else:
             env.CXXFLAGS += [
                 '-Wno-format-contains-nul',
                 '-Werror=unused-but-set-variable'
             ]
-            (major, minor, patchlevel) = cfg.env.CC_VERSION
-            if int(major) > 5 or (int(major) == 5 and int(minor) > 1):
+            if self.cc_version_gte(cfg, 5, 2):
                 env.CXXFLAGS += [
                     '-Werror=suggest-override',
                 ]
+            if self.cc_version_gte(cfg, 7, 4):
+                env.CXXFLAGS += [
+                    '-Werror=implicit-fallthrough',
+                ]
 
         if cfg.env.DEBUG:
             env.CXXFLAGS += [

libraries/AP_ADSB/AP_ADSB.cpp

@@ -938,6 +938,8 @@ void AP_ADSB::write_log(const adsb_vehicle_t &vehicle)
             if (!is_special_vehicle(vehicle.info.ICAO_address)) {
                 return;
             }
+            break;
+
         case logging::ALL:
             break;
 

libraries/AP_Airspeed/AP_Airspeed_SDP3X.cpp

@@ -205,7 +205,7 @@ float AP_Airspeed_SDP3X::_correct_pressure(float press)
     case AP_Airspeed::PITOT_TUBE_ORDER_NEGATIVE:
         press = -press;
         sign = -1.0f;
-    //FALLTHROUGH;
+        break;
     case AP_Airspeed::PITOT_TUBE_ORDER_POSITIVE:
         break;
     case AP_Airspeed::PITOT_TUBE_ORDER_AUTO:

libraries/AP_Baro/AP_Baro_BMP085.cpp

@@ -335,6 +335,7 @@ bool AP_Baro_BMP085::_data_ready()
         break;
     case BMP085_OVERSAMPLING_ULTRAHIGHRES:
         conversion_time_msec = 26;
+        break;
     default:
         break;
     }

libraries/AP_HAL/utility/dsm.cpp

@@ -281,6 +281,7 @@ dsm_decode(uint64_t frame_time, const uint8_t dsm_frame[16], uint16_t *values, u
 
 		case 2:
 			channel = 1;
+            break;
 
 		default:
 			break;

libraries/AP_RCProtocol/AP_RCProtocol_DSM.cpp

@@ -269,6 +269,7 @@ bool AP_RCProtocol_DSM::dsm_decode(uint32_t frame_time_ms, const uint8_t dsm_fra
 
         case 2:
             channel = 1;
+            break;
 
         default:
             break;