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

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Message-ID: <07999b46-ec31-4284-8869-1ecbdc0c7104@linuxfoundation.org>
Date: Wed, 25 Sep 2024 09:13:12 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: jstultz@...gle.com
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 tglx@...utronix.de, shuah@...nel.org, sboyd@...nel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 1/2] selftests:timers: posix_timers: Fix
 warn_unused_result in __fatal_error()

On 9/24/24 09:56, Shuah Khan 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);
> +
>   }
>   
>   #define fatal_error(name, what)	__fatal_error(__func__, name, what)

Any comments on this patch John?

thanks,
-- Shuah