linux-kernel - Re: [PATCH 1/2] selftests: timens: use 'llabs()' over 'abs()'

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Date:   Fri, 5 Nov 2021 13:26:49 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Anders Roxell <anders.roxell@...aro.org>
Cc:     shuah@...nel.org, nathan@...nel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 1/2] selftests: timens: use 'llabs()' over 'abs()'

On Fri, Nov 5, 2021 at 9:31 AM Anders Roxell <anders.roxell@...aro.org> wrote:
>
> When building selftests/timens with clang, the compiler warn about the
> function abs() see below:
>
> timerfd.c:64:7: error: absolute value function 'abs' given an argument of type 'long long' but has parameter of type 'int' which may cause truncation of value [-Werror,-Wabsolute-value]
>                 if (abs(elapsed - 3600) > 60) {
>                     ^
> timerfd.c:64:7: note: use function 'llabs' instead
>                 if (abs(elapsed - 3600) > 60) {
>                     ^~~
>                     llabs
>
> The note indicates what to do, Rework to use the function 'llabs()'.
>
> Signed-off-by: Anders Roxell <anders.roxell@...aro.org>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  tools/testing/selftests/timens/timer.c   | 2 +-
>  tools/testing/selftests/timens/timerfd.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/timens/timer.c b/tools/testing/selftests/timens/timer.c
> index 5e7f0051bd7b..5b939f59dfa4 100644
> --- a/tools/testing/selftests/timens/timer.c
> +++ b/tools/testing/selftests/timens/timer.c
> @@ -56,7 +56,7 @@ int run_test(int clockid, struct timespec now)
>                         return pr_perror("timerfd_gettime");
>
>                 elapsed = new_value.it_value.tv_sec;
> -               if (abs(elapsed - 3600) > 60) {
> +               if (llabs(elapsed - 3600) > 60) {
>                         ksft_test_result_fail("clockid: %d elapsed: %lld\n",
>                                               clockid, elapsed);
>                         return 1;
> diff --git a/tools/testing/selftests/timens/timerfd.c b/tools/testing/selftests/timens/timerfd.c
> index 9edd43d6b2c1..a4196bbd6e33 100644
> --- a/tools/testing/selftests/timens/timerfd.c
> +++ b/tools/testing/selftests/timens/timerfd.c
> @@ -61,7 +61,7 @@ int run_test(int clockid, struct timespec now)
>                         return pr_perror("timerfd_gettime(%d)", clockid);
>
>                 elapsed = new_value.it_value.tv_sec;
> -               if (abs(elapsed - 3600) > 60) {
> +               if (llabs(elapsed - 3600) > 60) {
>                         ksft_test_result_fail("clockid: %d elapsed: %lld\n",
>                                               clockid, elapsed);
>                         return 1;
> --
> 2.33.0
>


-- 
Thanks,
~Nick Desaulniers