# $(call cc-option, -W...) handles gcc -W.. options which
# are not supported by all versions of the compiler
ifdef KBUILD_ENABLE_EXTRA_GCC_CHECKS
+warning- := $(empty)
+
warning-1 := -Wextra -Wunused -Wno-unused-parameter
warning-1 += -Wmissing-declarations
warning-1 += -Wmissing-format-attribute
warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
warning-3 += $(call cc-option, -Wvla)
-warning := $(warning-$(KBUILD_ENABLE_EXTRA_GCC_CHECKS))
+warning := $(warning-$(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
+warning += $(warning-$(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
+warning += $(warning-$(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
-ifeq ("$(warning)","")
+ifeq ("$(strip $(warning))","")
$(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
endif