Patch "kbuild: move -Wunused-const-variable to W=1 warning level" has been added to the 4.6-stable tree

This is a note to let you know that I've just added the patch titled

kbuild: move -Wunused-const-variable to W=1 warning level

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kbuild-move-wunused-const-variable-to-w-1-warning-level.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnd Bergmann <[email protected]>
Date: Tue, 10 May 2016 23:30:01 +0200
Subject: kbuild: move -Wunused-const-variable to W=1 warning level

From: Arnd Bergmann <[email protected]>

commit c9c6837d39311b0cc14cdbe7c18e815ab44aefb1 upstream.

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.

---
 Makefile                   |    5 +++--
 scripts/Makefile.extrawarn |    1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

@@ -697,9 +697,10 @@ KBUILD_CFLAGS += $(call cc-option, -mno-
 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

@@ -24,6 +24,7 @@ warning-1 += $(call cc-option, -Wmissing
 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)
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.6/kbuild-move-wunused-const-variable-to-w-1-warning-level.patch queue-4.6/signal-move-generic-copy_siginfo-to-signal.h.patch