Re: [PATCH v2] selftests/resctrl: fix clang build warnings related to abs(), labs() calls

[John Hubbard]

On 5/7/24 6:21 PM, Reinette Chatre wrote:
> Hi John,
..
> The following (what was in v1) looks good to me. What am I missing?
>
> diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c
> index a81f91222a89..05a241519ae8 100644
> --- a/tools/testing/selftests/resctrl/cmt_test.c
> +++ b/tools/testing/selftests/resctrl/cmt_test.c
> @@ -40,11 +40,11 @@ static int show_results_info(unsigned long sum_llc_val, int no_of_bits,
>   	int ret;
>   
>   	avg_llc_val = sum_llc_val / num_of_runs;
> -	avg_diff = (long)abs(cache_span - avg_llc_val);
> +	avg_diff = (long)(cache_span - avg_llc_val);

This deletes the abs() call, because I incorrectly let clang's warning
lead me to believe that the abs() call was a no-op. But both you and Ilpo
pointed out that the math breaks if you do that.

>   	diff_percent = ((float)cache_span - avg_llc_val) / cache_span * 100;
>   
>   	ret = platform && abs((int)diff_percent) > max_diff_percent &&
> -	      abs(avg_diff) > max_diff;
> +	      labs(avg_diff) > max_diff;

This hunk is OK.

>   
>   	ksft_print_msg("%s Check cache miss rate within %lu%%\n",
>   		       ret ? "Fail:" : "Pass:", max_diff_percent);
>
> Reinette

thanks,
--
John Hubbard
NVIDIA