Messages in this thread Patch in this message | | | From | Guenter Roeck <> | Subject | [PATCH] linux/kernel.h: Fix warning seen with W=1 due to change in DIV_ROUND_CLOSEST | Date | Tue, 18 Sep 2012 21:00:09 -0700 |
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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> --- 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 594b419..2451f1f 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)); \ } \ -- 1.7.9.7
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