TGT_CFLAGS += -mmcu=$(MCU) $(OPT) $(CSTD) -g
TGT_CFLAGS += $(ARCH_FLAGS)
-TGT_CFLAGS += -Wextra -Wshadow -Wimplicit-function-declaration
+TGT_CFLAGS += -Wextra -Wshadow -Wimplicit-function-declaration -Wimplicit-fallthrough=1
TGT_CFLAGS += -Wredundant-decls -Wstrict-prototypes
TGT_CFLAGS += -fshort-enums -funsigned-bitfields
TGT_CFLAGS += -fno-common -ffunction-sections -fdata-sections