From 263a523d18bca306016d75f5c8d5c57c37fe52fb Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@roeck-us.net>
Date: Tue, 18 Sep 2012 20:42:31 -0700
Subject: [PATCH] linux/kernel.h: Fix warning seen with W=1 due to change in
DIV_ROUND_CLOSEST
After commit b6d86d3d (Fix DIV_ROUND_CLOSEST to support negative dividends),
the following warning is seen if the kernel is compiled with W=1 (-Wextra):
warning: comparison of unsigned expression >= 0 is always true
The warning is due to the test '((typeof(x))-1) >= 0', which is used to detect
if the variable type is unsigned. Research on the web suggests that the warning
disappears if '>' instead of '>=' is used for the comparison.
Tests after changing the macro along that line show that the warning is gone,
and that the result is still correct:
i=-4: DIV_ROUND_CLOSEST(i, 2)=-2
i=-3: DIV_ROUND_CLOSEST(i, 2)=-2
i=-2: DIV_ROUND_CLOSEST(i, 2)=-1
i=-1: DIV_ROUND_CLOSEST(i, 2)=-1
i=0: DIV_ROUND_CLOSEST(i, 2)=0
i=1: DIV_ROUND_CLOSEST(i, 2)=1
i=2: DIV_ROUND_CLOSEST(i, 2)=1
i=3: DIV_ROUND_CLOSEST(i, 2)=2
i=4: DIV_ROUND_CLOSEST(i, 2)=2
Code size is the same as before.
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Jean Delvare <khali@linux-fr.org>
---
include/linux/kernel.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 594b419b7d20..2451f1f7a1d9 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -91,7 +91,7 @@
{ \
typeof(x) __x = x; \
typeof(divisor) __d = divisor; \
- (((typeof(x))-1) >= 0 || (__x) >= 0) ? \
+ (((typeof(x))-1) > 0 || (__x) > 0) ? \
(((__x) + ((__d) / 2)) / (__d)) : \
(((__x) - ((__d) / 2)) / (__d)); \
} \
--
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