linux-kernel - [PATCH] input: appletouch: shut up -Wmaybe-uninitialized warning

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Message-Id: <20200107204300.1365789-1-arnd@arndb.de>
Date:   Tue,  7 Jan 2020 21:42:45 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Oleksandr Natalenko <oleksandr@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Richard Fontana <rfontana@...hat.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] input: appletouch: shut up -Wmaybe-uninitialized warning

Building with -O3 introduces a false-positive warning in this file:

In file included from include/linux/compiler_types.h:68,
                 from <command-line>:
drivers/input/mouse/appletouch.c: In function 'atp_complete_geyser_3_4':
include/linux/compiler-gcc.h:71:45: error: 'x_z' may be used uninitialized in this function [-Werror=maybe-uninitialized]
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
                                             ^~~~~~~~~~~~
drivers/input/mouse/appletouch.c:657:12: note: 'x_z' was declared here
  int x, y, x_z, y_z, x_f, y_f;
            ^~~
In file included from include/linux/compiler_types.h:68,
                 from <command-line>:
drivers/input/mouse/appletouch.c: In function 'atp_complete_geyser_1_2':
include/linux/compiler-gcc.h:71:45: error: 'x_z' may be used uninitialized in this function [-Werror=maybe-uninitialized]
 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
                                             ^~~~~~~~~~~~
drivers/input/mouse/appletouch.c:517:12: note: 'x_z' was declared here
  int x, y, x_z, y_z, x_f, y_f;
            ^~~

The variables are not actually used here since the only usage
happens when both 'x' and 'y' are non-zero, but this is something
that gcc fails to track.

Fixes: mmtom ("init/Kconfig: enable -O3 for all arches")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/input/mouse/appletouch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/mouse/appletouch.c b/drivers/input/mouse/appletouch.c
index 3f06e8a495d8..ec2139c43fcd 100644
--- a/drivers/input/mouse/appletouch.c
+++ b/drivers/input/mouse/appletouch.c
@@ -330,7 +330,7 @@ static void atp_reinit(struct work_struct *work)
 			retval);
 }
 
-static int atp_calculate_abs(struct atp *dev, int offset, int nb_sensors,
+static noinline int atp_calculate_abs(struct atp *dev, int offset, int nb_sensors,
 			     int fact, int *z, int *fingers)
 {
 	int i, pass;
-- 
2.20.0