Re: [PATCH] selftests/resctrl: fix clang build warnings related to abs(), labs() calls

[John Hubbard <jhubbard@nvidia.com>]

On 5/3/24 1:00 AM, Ilpo Järvinen wrote:
> On Thu, 2 May 2024, John Hubbard wrote:
...
>> diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
>> index d67ffa3ec63a..c873793d016d 100644
>> --- a/tools/testing/selftests/resctrl/mbm_test.c
>> +++ b/tools/testing/selftests/resctrl/mbm_test.c
>> @@ -33,7 +33,7 @@ show_bw_info(unsigned long *bw_imc, unsigned long *bw_resc, size_t span)
>>   
>>   	avg_bw_imc = sum_bw_imc / 4;
>>   	avg_bw_resc = sum_bw_resc / 4;
>> -	avg_diff = (float)labs(avg_bw_resc - avg_bw_imc) / avg_bw_imc;
>> +	avg_diff = (float)(avg_bw_resc - avg_bw_imc) / avg_bw_imc;
>>   	avg_diff_per = (int)(avg_diff * 100);
>>   
>>   	ret = avg_diff_per > MAX_DIFF_PERCENT;
> 
> But how are these two cases same after your change when you ended up
> removing taking the absolute value entirely?

All of the arguments are unsigned integers, so all arithmetic results
are interpreted as unsigned, so taking the absolute value of that is
always a no-op.

thanks,
-- 
John Hubbard
NVIDIA