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From: Arnd Bergmann <arnd@arndb.de>
To: Michal Marek <mmarek@suse.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Peter Oberparleiter <oberpar@linux.vnet.ibm.com>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH 2/5] Kbuild: disable 'maybe-uninitialized' warning for CONFIG_PROFILE_ALL_BRANCHES
Date: Fri, 12 Feb 2016 17:06:19 +0100	[thread overview]
Message-ID: <1455293187-179811-3-git-send-email-arnd@arndb.de> (raw)
In-Reply-To: <1455293187-179811-1-git-send-email-arnd@arndb.de>

CONFIG_PROFILE_ALL_BRANCHES confuses gcc-5.x to the degree that it prints
incorrect warnings about a lot of variables that it thinks can be used
uninitialized, e.g.:

i2c/busses/i2c-diolan-u2c.c: In function 'diolan_usb_xfer':
i2c/busses/i2c-diolan-u2c.c:391:16: warning: 'byte' may be used uninitialized in this function
iio/gyro/itg3200_core.c: In function 'itg3200_probe':
iio/gyro/itg3200_core.c:213:6: warning: 'val' may be used uninitialized in this function
leds/leds-lp55xx-common.c: In function 'lp55xx_update_bits':
leds/leds-lp55xx-common.c:350:6: warning: 'tmp' may be used uninitialized in this function
misc/bmp085.c: In function 'show_pressure':
misc/bmp085.c:363:10: warning: 'pressure' may be used uninitialized in this function
power/ds2782_battery.c: In function 'ds2786_get_capacity':
power/ds2782_battery.c:214:17: warning: 'raw' may be used uninitialized in this function

These are all false positives that either rob someone's time when trying
to figure out whether they are real, or they get people to send wrong
patches to shut up the warnings.

Nobody normally wants to run a CONFIG_PROFILE_ALL_BRANCHES kernel in
production, so disabling the whole class of warnings for this configuration
has no serious downsides either.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 Makefile | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 9092c16fa6cf..352f55ccc54e 100644
--- a/Makefile
+++ b/Makefile
@@ -617,7 +617,11 @@ KBUILD_CFLAGS	+= $(call cc-option,-fno-delete-null-pointer-checks,)
 ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
 KBUILD_CFLAGS	+= -Os $(call cc-disable-warning,maybe-uninitialized,)
 else
-KBUILD_CFLAGS	+= -O2
+ifdef CONFIG_PROFILE_ALL_BRANCHES
+KBUILD_CFLAGS	+= -O2 $(call cc-disable-warning,maybe-uninitialized,)
+else
+KBUILD_CFLAGS   += -O2
+endif
 endif
 
 # Tell gcc to never replace conditional load with a non-conditional one
-- 
2.7.0

WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/5] Kbuild: disable 'maybe-uninitialized' warning for CONFIG_PROFILE_ALL_BRANCHES
Date: Fri, 12 Feb 2016 17:06:19 +0100	[thread overview]
Message-ID: <1455293187-179811-3-git-send-email-arnd@arndb.de> (raw)
In-Reply-To: <1455293187-179811-1-git-send-email-arnd@arndb.de>

CONFIG_PROFILE_ALL_BRANCHES confuses gcc-5.x to the degree that it prints
incorrect warnings about a lot of variables that it thinks can be used
uninitialized, e.g.:

i2c/busses/i2c-diolan-u2c.c: In function 'diolan_usb_xfer':
i2c/busses/i2c-diolan-u2c.c:391:16: warning: 'byte' may be used uninitialized in this function
iio/gyro/itg3200_core.c: In function 'itg3200_probe':
iio/gyro/itg3200_core.c:213:6: warning: 'val' may be used uninitialized in this function
leds/leds-lp55xx-common.c: In function 'lp55xx_update_bits':
leds/leds-lp55xx-common.c:350:6: warning: 'tmp' may be used uninitialized in this function
misc/bmp085.c: In function 'show_pressure':
misc/bmp085.c:363:10: warning: 'pressure' may be used uninitialized in this function
power/ds2782_battery.c: In function 'ds2786_get_capacity':
power/ds2782_battery.c:214:17: warning: 'raw' may be used uninitialized in this function

These are all false positives that either rob someone's time when trying
to figure out whether they are real, or they get people to send wrong
patches to shut up the warnings.

Nobody normally wants to run a CONFIG_PROFILE_ALL_BRANCHES kernel in
production, so disabling the whole class of warnings for this configuration
has no serious downsides either.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 Makefile | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 9092c16fa6cf..352f55ccc54e 100644
--- a/Makefile
+++ b/Makefile
@@ -617,7 +617,11 @@ KBUILD_CFLAGS	+= $(call cc-option,-fno-delete-null-pointer-checks,)
 ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
 KBUILD_CFLAGS	+= -Os $(call cc-disable-warning,maybe-uninitialized,)
 else
-KBUILD_CFLAGS	+= -O2
+ifdef CONFIG_PROFILE_ALL_BRANCHES
+KBUILD_CFLAGS	+= -O2 $(call cc-disable-warning,maybe-uninitialized,)
+else
+KBUILD_CFLAGS   += -O2
+endif
 endif
 
 # Tell gcc to never replace conditional load with a non-conditional one
-- 
2.7.0

  parent reply	other threads:[~2016-02-12 16:07 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-12 16:06 [PATCH 0/5] gcov fixes and maybe-uninitialized warnings Arnd Bergmann
2016-02-12 16:06 ` Arnd Bergmann
2016-02-12 16:06 ` [PATCH 1/5] Kbuild: change CC_OPTIMIZE_FOR_SIZE definition Arnd Bergmann
2016-02-12 16:06   ` Arnd Bergmann
2016-02-12 16:06 ` Arnd Bergmann [this message]
2016-02-12 16:06   ` [PATCH 2/5] Kbuild: disable 'maybe-uninitialized' warning for CONFIG_PROFILE_ALL_BRANCHES Arnd Bergmann
2016-02-15 17:46   ` Steven Rostedt
2016-02-15 17:46     ` Steven Rostedt
2016-02-12 16:06 ` [PATCH 3/5] gcov: disable for COMPILE_TEST Arnd Bergmann
2016-02-12 16:06   ` Arnd Bergmann
2016-02-15 14:23   ` Peter Oberparleiter
2016-02-15 14:23     ` Peter Oberparleiter
2016-02-12 16:06 ` [PATCH 4/5] gcov: disable tree-loop-im to reduce stack usage Arnd Bergmann
2016-02-12 16:06   ` Arnd Bergmann
2016-02-15 14:34   ` Peter Oberparleiter
2016-02-15 14:34     ` Peter Oberparleiter
2016-02-12 16:06 ` [PATCH 5/5] gcov: disable -Wmaybe-uninitialized warning Arnd Bergmann
2016-02-12 16:06   ` Arnd Bergmann
2016-02-15 14:35   ` Peter Oberparleiter
2016-02-15 14:35     ` Peter Oberparleiter
2016-04-25 15:35 [RESEND PATCH 0/5] gcov fixes and maybe-uninitialized warnings Arnd Bergmann
2016-04-25 15:35 ` [PATCH 2/5] Kbuild: disable 'maybe-uninitialized' warning for CONFIG_PROFILE_ALL_BRANCHES Arnd Bergmann
2016-04-25 15:35   ` Arnd Bergmann

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