Re: [PATCH 3/3] ath9k: fix 'side effect in macro' smatch warning

[Ben Greear <greearb@candelatech.com>]

On 06/21/2012 12:07 PM, Rajkumar Manoharan wrote:
> On Thu, Jun 21, 2012 at 11:42:53AM -0700, Ben Greear wrote:
>> On 06/21/2012 11:31 AM, Rajkumar Manoharan wrote:
>>> ath9k_get_et_stats() warn: side effect in macro
>>> 'AWDATA' doing 'i++'
>>>
>>> Cc: Ben Greear<greearb@candelatech.com>
>>> Signed-off-by: Rajkumar Manoharan<rmanohar@qca.qualcomm.com>
>>> ---
>>>   drivers/net/wireless/ath/ath9k/main.c | 9 +++++----
>>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
>>> index 85f9ab4..32474b0 100644
>>> --- a/drivers/net/wireless/ath/ath9k/main.c
>>> +++ b/drivers/net/wireless/ath/ath9k/main.c
>>> @@ -2003,10 +2003,11 @@ static int ath9k_get_et_sset_count(struct ieee80211_hw *hw,
>>>   #define PR_QNUM(_n) (sc->tx.txq_map[_n]->axq_qnum)
>>>   #define AWDATA(elem)							\
>>>   	do {								\
>>> -		data[i++] = sc->debug.stats.txstats[PR_QNUM(WME_AC_BE)].elem; \
>>> -		data[i++] = sc->debug.stats.txstats[PR_QNUM(WME_AC_BK)].elem; \
>>> -		data[i++] = sc->debug.stats.txstats[PR_QNUM(WME_AC_VI)].elem; \
>>> -		data[i++] = sc->debug.stats.txstats[PR_QNUM(WME_AC_VO)].elem; \
>>> +		data[i+0] = sc->debug.stats.txstats[PR_QNUM(WME_AC_BE)].elem; \
>>> +		data[i+1] = sc->debug.stats.txstats[PR_QNUM(WME_AC_BK)].elem; \
>>> +		data[i+2] = sc->debug.stats.txstats[PR_QNUM(WME_AC_VI)].elem; \
>>> +		data[i+3] = sc->debug.stats.txstats[PR_QNUM(WME_AC_VO)].elem; \
>>> +		i += 4; \
>>>   	} while (0)
>>
>> The macro is still changing i.  So, whatever smatch is, seems it
>> should still warn, or it's broken :P
>>
> No it is not. The warning message is a hint. The smatch assumes that replacing
> the macro 'i++' might cause unexpected behaviour like 5++ in each statement.

Well, my opinion is that your patch only adds un-needed code and that
smatch is either currently giving false-positives, or that it is
missing a warning when you add your patch.

But, not a big deal either way.

Thanks,
Ben

>
> -Rajkumar


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com