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

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Message-ID: <c1e834d6-266d-d8bb-4e85-cdc440ddcb31@linux.intel.com>
Date: Fri, 10 May 2024 12:06:02 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: John Hubbard <jhubbard@...dia.com>
cc: Shuah Khan <shuah@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
    Nick Desaulniers <ndesaulniers@...gle.com>, 
    Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
    Fenghua Yu <fenghua.yu@...el.com>, 
    Reinette Chatre <reinette.chatre@...el.com>, 
    Valentin Obst <kernel@...entinobst.de>, linux-kselftest@...r.kernel.org, 
    LKML <linux-kernel@...r.kernel.org>, llvm@...ts.linux.dev
Subject: Re: [PATCH] selftests/resctrl: fix clang build warnings related to
 abs(), labs() calls

On Wed, 8 May 2024, John Hubbard wrote:

> When building with clang, via:
> 
>     make LLVM=1 -C tools/testing/selftests
> 
> ...two types of warnings occur:
> 
>     warning: absolute value function 'abs' given an argument of type
>     'long' but has parameter of type 'int' which may cause truncation of
>     value
> 
>     warning: taking the absolute value of unsigned type 'unsigned long'
>     has no effect
> 
> Fix these by:
> 
> a) using labs() in place of abs(), when long integers are involved, and
> 
> b) Change to use signed integer data types, in places where subtraction
>    is used (and could end up with negative values).
> 
> c) Remove a duplicate abs() call in cmt_test.c.

In general, instead of filename, it's better to refer to the actual 
function in this kind of description. And in this particular case, 
cmt_test.c could be replaced with "the CMT selftest" which is more 
descriptive and still unambiguous.

> Cc: Reinette Chatre <reinette.chatre@...el.com>
> Cc: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>

Thank you.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.

> ---
>  tools/testing/selftests/resctrl/cmt_test.c | 4 ++--
>  tools/testing/selftests/resctrl/mba_test.c | 2 +-
>  tools/testing/selftests/resctrl/mbm_test.c | 2 +-
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> 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);
>  	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;
>  
>  	ksft_print_msg("%s Check cache miss rate within %lu%%\n",
>  		       ret ? "Fail:" : "Pass:", max_diff_percent);
> diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
> index 7946e32e85c8..5fffbc9ff6a4 100644
> --- a/tools/testing/selftests/resctrl/mba_test.c
> +++ b/tools/testing/selftests/resctrl/mba_test.c
> @@ -60,7 +60,7 @@ static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
>  	/* Memory bandwidth from 100% down to 10% */
>  	for (allocation = 0; allocation < ALLOCATION_MAX / ALLOCATION_STEP;
>  	     allocation++) {
> -		unsigned long avg_bw_imc, avg_bw_resc;
> +		long avg_bw_imc, avg_bw_resc;
>  		unsigned long sum_bw_imc = 0, sum_bw_resc = 0;
>  		int avg_diff_per;
>  		float avg_diff;
> diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
> index d67ffa3ec63a..a4c3ea49b0e8 100644
> --- a/tools/testing/selftests/resctrl/mbm_test.c
> +++ b/tools/testing/selftests/resctrl/mbm_test.c
> @@ -17,7 +17,7 @@
>  static int
>  show_bw_info(unsigned long *bw_imc, unsigned long *bw_resc, size_t span)
>  {
> -	unsigned long avg_bw_imc = 0, avg_bw_resc = 0;
> +	long avg_bw_imc = 0, avg_bw_resc = 0;
>  	unsigned long sum_bw_imc = 0, sum_bw_resc = 0;
>  	int runs, ret, avg_diff_per;
>  	float avg_diff = 0;
> 
> base-commit: 45db3ab70092637967967bfd8e6144017638563c
> prerequisite-patch-id: b901ece2a5b78503e2fb5480f20e304d36a0ea27
> prerequisite-patch-id: 8d96c4b8c3ed6d9ea2588ef7f594ae0f9f83c279
>