AP_UAVCAN: silence function cast warning/error for Registry template

libraries/AP_UAVCAN/AP_UAVCAN.h

@@ -54,18 +54,31 @@ class TrafficReportCb;
 class ActuatorStatusCb;
 class ESCStatusCb;
 
+#if defined(__GNUC__) && (__GNUC__ > 8)
+#define DISABLE_W_CAST_FUNCTION_TYPE_PUSH \
+    _Pragma("GCC diagnostic push") \
+    _Pragma("GCC diagnostic ignored \"-Wcast-function-type\"")
+#define DISABLE_W_CAST_FUNCTION_TYPE_POP \
+    _Pragma("GCC diagnostic pop")
+#else
+#define DISABLE_W_CAST_FUNCTION_TYPE_PUSH
+#define DISABLE_W_CAST_FUNCTION_TYPE_POP
+#endif
+
 /*
     Frontend Backend-Registry Binder: Whenever a message of said DataType_ from new node is received,
     the Callback will invoke registery to register the node as separate backend.
 */
 #define UC_REGISTRY_BINDER(ClassName_, DataType_) \
-	class ClassName_ : public AP_UAVCAN::RegistryBinder<DataType_> { \
+    class ClassName_ : public AP_UAVCAN::RegistryBinder<DataType_> { \
         typedef void (*CN_Registry)(AP_UAVCAN*, uint8_t, const ClassName_&); \
-	    public: \
+        public: \
-	        ClassName_() : RegistryBinder() {} \
+            ClassName_() : RegistryBinder() {} \
-	        ClassName_(AP_UAVCAN* uc,  CN_Registry ffunc) : \
+            DISABLE_W_CAST_FUNCTION_TYPE_PUSH \
-				RegistryBinder(uc, (Registry)ffunc) {} \
+            ClassName_(AP_UAVCAN* uc,  CN_Registry ffunc) : \
-	}
+                RegistryBinder(uc, (Registry)ffunc) {} \
+            DISABLE_W_CAST_FUNCTION_TYPE_POP \
+    }
 
 class AP_UAVCAN : public AP_CANDriver {
 public: