linux-kernel - [PATCH 2/4] drivers/thermal: decrement sizeof size in strncmp

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Date:	Thu, 12 Nov 2009 08:49:04 +0100 (CET)
From:	Julia Lawall <julia@...u.dk>
To:	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 2/4] drivers/thermal: decrement sizeof size in strncmp

From: Julia Lawall <julia@...u.dk>

As observed by Joe Perches, sizeof of a constant string includes the
trailing 0.  If what is wanted is to check the initial characters of
another string, this trailing 0 should not be taken into account.  If an
exact match is wanted, strcmp should be used instead.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression foo;
constant char *abc;
@@

strncmp(foo, abc, 
- sizeof(abc)
+ sizeof(abc)-1
 )
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>

---
 drivers/thermal/thermal_sys.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -u -p a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
--- a/drivers/thermal/thermal_sys.c
+++ b/drivers/thermal/thermal_sys.c
@@ -147,9 +147,9 @@ mode_store(struct device *dev, struct de
 	if (!tz->ops->set_mode)
 		return -EPERM;
 
-	if (!strncmp(buf, "enabled", sizeof("enabled")))
+	if (!strncmp(buf, "enabled", sizeof("enabled") - 1))
 		result = tz->ops->set_mode(tz, THERMAL_DEVICE_ENABLED);
-	else if (!strncmp(buf, "disabled", sizeof("disabled")))
+	else if (!strncmp(buf, "disabled", sizeof("disabled") - 1))
 		result = tz->ops->set_mode(tz, THERMAL_DEVICE_DISABLED);
 	else
 		result = -EINVAL;
--
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