On Tue, 10 May 2016, Arnd Bergmann wrote: > 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@xxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > --- > I had originally started testing with gcc-6 a while ago and turned off > this option in my build scripts because it was too noisy. I fixed all > the other warnings I got and forgot about it until Olof mentioned it > when he upgraded his build bot and the warnings started exploding. > > Makefile | 5 +++-- > scripts/Makefile.extrawarn | 1 + > 2 files changed, 4 insertions(+), 2 deletions(-) Works for me: Acked-by: Lee Jones <lee.jones@xxxxxxxxxx> OOI, we described W=1 as "warnings that we'd like to see fixed shortly, in order to obtain a clean W=1 build". By demoting 'sign-compare' to W=2 we reduced warnings from 25k to 3k, which is a more achievable target. How does this change effect the W=1 warning count? Does it place a clean W=1 build back out of the realms of possibility? > diff --git a/Makefile b/Makefile > index f7ccd8a40450..7934088c011b 100644 > --- a/Makefile > +++ b/Makefile > @@ -708,9 +708,10 @@ KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,) > KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior) > else > > -# This warning generated too much noise in a regular build. > -# Use make W=1 to enable this warning (see scripts/Makefile.build) > +# These warnings generated too much noise in a regular build. > +# Use make W=1 to enable them (see scripts/Makefile.build) > KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) > +KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) > endif > > ifdef CONFIG_FRAME_POINTER > diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn > index f9e47a70509c..53449a6ff6aa 100644 > --- a/scripts/Makefile.extrawarn > +++ b/scripts/Makefile.extrawarn > @@ -24,6 +24,7 @@ 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) > -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
