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From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Date: Fri, 10 May 2024 12:06:02 +0300 (EEST)
To: John Hubbard <jhubbard@nvidia.com>
cc: Shuah Khan <shuah@kernel.org>, Nathan Chancellor <nathan@kernel.org>, 
    Nick Desaulniers <ndesaulniers@google.com>, 
    Bill Wendling <morbo@google.com>, Justin Stitt <justinstitt@google.com>, 
    Fenghua Yu <fenghua.yu@intel.com>, 
    Reinette Chatre <reinette.chatre@intel.com>, 
    Valentin Obst <kernel@valentinobst.de>, linux-kselftest@vger.kernel.org, 
    LKML <linux-kernel@vger.kernel.org>, llvm@lists.linux.dev
Subject: Re: [PATCH] selftests/resctrl: fix clang build warnings related to
 abs(), labs() calls
In-Reply-To: <20240508190254.266892-1-jhubbard@nvidia.com>
Message-ID: <c1e834d6-266d-d8bb-4e85-cdc440ddcb31@linux.intel.com>
References: <20240508190254.266892-1-jhubbard@nvidia.com>
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On Wed, 8 May 2024, John Hubbard wrote:

> When building with clang, via:
>=20
>     make LLVM=3D1 -C tools/testing/selftests
>=20
> ...two types of warnings occur:
>=20
>     warning: absolute value function 'abs' given an argument of type
>     'long' but has parameter of type 'int' which may cause truncation of
>     value
>=20
>     warning: taking the absolute value of unsigned type 'unsigned long'
>     has no effect
>=20
> Fix these by:
>=20
> a) using labs() in place of abs(), when long integers are involved, and
>=20
> b) Change to use signed integer data types, in places where subtraction
>    is used (and could end up with negative values).
>=20
> c) Remove a duplicate abs() call in cmt_test.c.

In general, instead of filename, it's better to refer to the actual=20
function in this kind of description. And in this particular case,=20
cmt_test.c could be replaced with "the CMT selftest" which is more=20
descriptive and still unambiguous.

> Cc: Reinette Chatre <reinette.chatre@intel.com>
> Cc: Ilpo J=C3=A4rvinen <ilpo.jarvinen@linux.intel.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Thank you.

Reviewed-by: Ilpo J=C3=A4rvinen <ilpo.jarvinen@linux.intel.com>

--=20
 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(-)
>=20
> diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/s=
elftests/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_va=
l, int no_of_bits,
>  =09int ret;
> =20
>  =09avg_llc_val =3D sum_llc_val / num_of_runs;
> -=09avg_diff =3D (long)abs(cache_span - avg_llc_val);
> +=09avg_diff =3D (long)(cache_span - avg_llc_val);
>  =09diff_percent =3D ((float)cache_span - avg_llc_val) / cache_span * 100=
;
> =20
>  =09ret =3D platform && abs((int)diff_percent) > max_diff_percent &&
> -=09      abs(avg_diff) > max_diff;
> +=09      labs(avg_diff) > max_diff;
> =20
>  =09ksft_print_msg("%s Check cache miss rate within %lu%%\n",
>  =09=09       ret ? "Fail:" : "Pass:", max_diff_percent);
> diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/s=
elftests/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, unsign=
ed long *bw_resc)
>  =09/* Memory bandwidth from 100% down to 10% */
>  =09for (allocation =3D 0; allocation < ALLOCATION_MAX / ALLOCATION_STEP;
>  =09     allocation++) {
> -=09=09unsigned long avg_bw_imc, avg_bw_resc;
> +=09=09long avg_bw_imc, avg_bw_resc;
>  =09=09unsigned long sum_bw_imc =3D 0, sum_bw_resc =3D 0;
>  =09=09int avg_diff_per;
>  =09=09float avg_diff;
> diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/s=
elftests/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)
>  {
> -=09unsigned long avg_bw_imc =3D 0, avg_bw_resc =3D 0;
> +=09long avg_bw_imc =3D 0, avg_bw_resc =3D 0;
>  =09unsigned long sum_bw_imc =3D 0, sum_bw_resc =3D 0;
>  =09int runs, ret, avg_diff_per;
>  =09float avg_diff =3D 0;
>=20
> base-commit: 45db3ab70092637967967bfd8e6144017638563c
> prerequisite-patch-id: b901ece2a5b78503e2fb5480f20e304d36a0ea27
> prerequisite-patch-id: 8d96c4b8c3ed6d9ea2588ef7f594ae0f9f83c279
>=20
--8323328-1600665862-1715331962=:1562--