linux-stable/scripts/Makefile.extrawarn
Arnd Bergmann c9c6837d39 kbuild: move -Wunused-const-variable to W=1 warning level
gcc-6 started warning by default about variables that are not
used anywhere and that are marked 'const', generating many
false positives in an allmodconfig build, e.g.:

arch/arm/mach-davinci/board-da830-evm.c:282:20: warning: 'da830_evm_emif25_pins' defined but not used [-Wunused-const-variable=]
arch/arm/plat-omap/dmtimer.c:958:34: warning: 'omap_timer_match' defined but not used [-Wunused-const-variable=]
drivers/bluetooth/hci_bcm.c:625:39: warning: 'acpi_bcm_default_gpios' defined but not used [-Wunused-const-variable=]
drivers/char/hw_random/omap-rng.c:92:18: warning: 'reg_map_omap4' defined but not used [-Wunused-const-variable=]
drivers/devfreq/exynos/exynos5_bus.c:381:32: warning: 'exynos5_busfreq_int_pm' defined but not used [-Wunused-const-variable=]
drivers/dma/mv_xor.c:1139:34: warning: 'mv_xor_dt_ids' defined but not used [-Wunused-const-variable=]

This is similar to the existing -Wunused-but-set-variable warning
that was added in an earlier release and that we disable by default
now and only enable when W=1 is set, so it makes sense to do
the same here. Once we have eliminated the majority of the
warnings for both, we can put them back into the default list.

We probably want this in backport kernels as well, to allow building
them with gcc-6 without introducing extra warnings.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Lee Jones <lee.jones@linaro.org>
Cc: stable@vger.kernel.org
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-05-11 13:05:40 +02:00

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# ==========================================================================
#
# make W=... settings
#
# W=1 - warnings that may be relevant and does not occur too often
# W=2 - warnings that occur quite often but may still be relevant
# W=3 - the more obscure warnings, can most likely be ignored
#
# $(call cc-option, -W...) handles gcc -W.. options which
# are not supported by all versions of the compiler
# ==========================================================================
ifeq ("$(origin W)", "command line")
export KBUILD_ENABLE_EXTRA_GCC_CHECKS := $(W)
endif
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-1 += $(call cc-option, -Wmissing-prototypes)
warning-1 += -Wold-style-definition
warning-1 += $(call cc-option, -Wmissing-include-dirs)
warning-1 += $(call cc-option, -Wunused-but-set-variable)
warning-1 += $(call cc-option, -Wunused-const-variable)
warning-1 += $(call cc-disable-warning, missing-field-initializers)
warning-1 += $(call cc-disable-warning, sign-compare)
warning-2 := -Waggregate-return
warning-2 += -Wcast-align
warning-2 += -Wdisabled-optimization
warning-2 += -Wnested-externs
warning-2 += -Wshadow
warning-2 += $(call cc-option, -Wlogical-op)
warning-2 += $(call cc-option, -Wmissing-field-initializers)
warning-2 += $(call cc-option, -Wsign-compare)
warning-3 := -Wbad-function-cast
warning-3 += -Wcast-qual
warning-3 += -Wconversion
warning-3 += -Wpacked
warning-3 += -Wpadded
warning-3 += -Wpointer-arith
warning-3 += -Wredundant-decls
warning-3 += -Wswitch-default
warning-3 += $(call cc-option, -Wpacked-bitfield-compat)
warning-3 += $(call cc-option, -Wvla)
warning := $(warning-$(findstring 1, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
warning += $(warning-$(findstring 2, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
warning += $(warning-$(findstring 3, $(KBUILD_ENABLE_EXTRA_GCC_CHECKS)))
ifeq ("$(strip $(warning))","")
$(error W=$(KBUILD_ENABLE_EXTRA_GCC_CHECKS) is unknown)
endif
KBUILD_CFLAGS += $(warning)
else
ifeq ($(cc-name),clang)
KBUILD_CFLAGS += $(call cc-disable-warning, initializer-overrides)
KBUILD_CFLAGS += $(call cc-disable-warning, unused-value)
KBUILD_CFLAGS += $(call cc-disable-warning, format)
KBUILD_CFLAGS += $(call cc-disable-warning, unknown-warning-option)
KBUILD_CFLAGS += $(call cc-disable-warning, sign-compare)
KBUILD_CFLAGS += $(call cc-disable-warning, format-zero-length)
KBUILD_CFLAGS += $(call cc-disable-warning, uninitialized)
endif
endif