linux-kernel - Re: [PATCH 1/2] selftests:timers: posix_timers: Fix warn_unused_result in __fatal

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Message-ID: <CANDhNCoC50Mhyo19O2drqXU7g-3j+wkFteTyi1jg1_5pCyzwYQ@mail.gmail.com>
Date: Wed, 25 Sep 2024 10:19:38 -0700
From: John Stultz <jstultz@...gle.com>
To: Shuah Khan <skhan@...uxfoundation.org>
Cc: tglx@...utronix.de, sboyd@...nel.org, shuah@...nel.org, 
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 1/2] selftests:timers: posix_timers: Fix
 warn_unused_result in __fatal_error()

On Tue, Sep 24, 2024 at 8:57 AM Shuah Khan <skhan@...uxfoundation.org> wrote:
>
> __fatal_error routine doesn't check strerror_r() return value,
> which results in the following compile time warning:
>
> posix_timers.c: In function ‘__fatal_error’:
> posix_timers.c:31:9: warning: ignoring return value of ‘strerror_r’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
>    31 |         strerror_r(errno, buf, sizeof(buf));
>
> Fix this by adding a check for return value and error handling appropriate
> for the GNU-specific strerror_r() in use in __fatal_error(). Check if
> return string is null and handle accordingly.
>
> From Linux strerror_r() manual page:
>
> "The GNU-specific strerror_r() returns a pointer to a string containing
> the error message. This may be either a pointer to a string that the
> function stores in buf, or a pointer to some (immutable) static string
> (in which case buf is unused). If the function stores a string in buf,
> then at most buflen bytes are stored (the string may be truncated if
> buflen is too small and errnum is unknown). The string always includes
> a terminating null byte."
>
> Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
> ---
>  tools/testing/selftests/timers/posix_timers.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
> index 16bd49492efa..ddb1cebc844e 100644
> --- a/tools/testing/selftests/timers/posix_timers.c
> +++ b/tools/testing/selftests/timers/posix_timers.c
> @@ -26,13 +26,17 @@
>  static void __fatal_error(const char *test, const char *name, const char *what)
>  {
>         char buf[64];
> +       char *ret_str = NULL;
>
> -       strerror_r(errno, buf, sizeof(buf));
> +       ret_str = strerror_r(errno, buf, sizeof(buf));
>
> -       if (name && strlen(name))
> -               ksft_exit_fail_msg("%s %s %s %s\n", test, name, what, buf);
> +       if (name && strlen(name) && ret_str)
> +               ksft_exit_fail_msg("%s %s %s %s\n", test, name, what, ret_str);
> +       else if (ret_str)
> +               ksft_exit_fail_msg("%s %s %s\n", test, what, ret_str);
>         else
> -               ksft_exit_fail_msg("%s %s %s\n", test, what, buf);
> +               ksft_exit_fail_msg("%s %s\n", test, what);
> +
>  }

Acked-by: John Stultz <jstultz@...gle.com>