From d41b89cca5f26bbafb496a93c4a48cdf282833ee Mon Sep 17 00:00:00 2001 From: Dimitry Andric Date: Sun, 23 Nov 2014 18:31:55 +0000 Subject: [PATCH] Fix the following -Werror warning from clang 3.5.0, while building the ath kernel module: sys/dev/ath/ath_hal/ar5212/ar5212_reset.c:2642:7: error: taking the absolute value of unsigned type 'unsigned int' has no effect [-Werror,-Wabsolute-value] if (abs(lp[0] * EEP_SCALE - target) < EEP_DELTA) { ^ sys/dev/ath/ah_osdep.h:74:18: note: expanded from macro 'abs' #define abs(_a) __builtin_abs(_a) ^ sys/dev/ath/ath_hal/ar5212/ar5212_reset.c:2642:7: note: remove the call to '__builtin_abs' since unsigned values cannot be negative sys/dev/ath/ah_osdep.h:74:18: note: expanded from macro 'abs' #define abs(_a) __builtin_abs(_a) ^ 1 error generated. This warning occurs because both lp[0] and target are unsigned, so the subtraction expression is also unsigned, and calling abs() is a no-op. However, the intention was to look at the absolute difference between the two unsigned quantities. Introduce a small static function to clarify what we're doing, and call that instead. Reviewed by: adrian MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D1212 --- sys/dev/ath/ath_hal/ar5212/ar5212_reset.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c b/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c index eca2e1f36571..ccdccb611094 100644 --- a/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c +++ b/sys/dev/ath/ath_hal/ar5212/ar5212_reset.c @@ -2605,6 +2605,12 @@ ar5212GetTargetPowers(struct ath_hal *ah, const struct ieee80211_channel *chan, powInfo[ixlo].twicePwr54, powInfo[ixhi].twicePwr54); } +static uint32_t +udiff(uint32_t u, uint32_t v) +{ + return (u >= v ? u - v : v - u); +} + /* * Search a list for a specified value v that is within * EEP_DELTA of the search values. Return the closest @@ -2639,7 +2645,7 @@ ar5212GetLowerUpperValues(uint16_t v, uint16_t *lp, uint16_t listSize, * If value is close to the current value of the list * then target is not between values, it is one of the values */ - if (abs(lp[0] * EEP_SCALE - target) < EEP_DELTA) { + if (udiff(lp[0] * EEP_SCALE, target) < EEP_DELTA) { *vlo = *vhi = lp[0]; return; }