linux-kernel - Re: [PATCH] selftests/harness: fix many "format string is empty" warnings

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Message-ID: <20240501151343.GA1018661@dev-arch.thelio-3990X>
Date: Wed, 1 May 2024 08:13:43 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: John Hubbard <jhubbard@...dia.com>
Cc: Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Valentin Obst <kernel@...entinobst.de>,
	Kees Cook <keescook@...omium.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Bill Wendling <morbo@...gle.com>
Subject: Re: [PATCH] selftests/harness: fix many "format string is empty"
 warnings

Hi John,

On Tue, Apr 30, 2024 at 07:08:13PM -0700, John Hubbard wrote:
> In order to build with clang at all, in order to see these symptoms, one
> must first apply Valentin Obst's build fix for LLVM [1]. Once that is
> done, then when building with clang, via:
> 
>     make LLVM=1 -C tools/testing/selftests
> 
> ...clang emits a "format string is empty" warning. (gcc also emits a
> similar warning.)

The warning you are describing here sounds like the same exact one that
commit caed8eba2215 ("selftests: kselftest_harness: fix Clang warning
about zero-length format") should have addressed in 6.9-rc5. Is this
patch actually necessary?

> Fix by passing NULL, instead of "", for the msg argument to

Because this text is describing what was done in caed8eba2215...

> ksft_test_result_code(). This removes dozens of warnings and a few
> errors (some tests have -Werror set).
>
> [1] https://lore.kernel.org/all/20240329-selftests-libmk-llvm-rfc-v1-1-2f9ed7d1c49f@valentinobst.de/
> 
> Cc: Valentin Obst <kernel@...entinobst.de>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> Cc: Nathan Chancellor <nathan@...nel.org>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Justin Stitt <justinstitt@...gle.com>
> Cc: Bill Wendling <morbo@...gle.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
>  tools/testing/selftests/kselftest_harness.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
> index d98702b6955d..456b8694e678 100644
> --- a/tools/testing/selftests/kselftest_harness.h
> +++ b/tools/testing/selftests/kselftest_harness.h
> @@ -1207,8 +1207,10 @@ void __run_test(struct __fixture_metadata *f,
>  	else
>  		diagnostic = "unknown";
>  
> -	ksft_test_result_code(t->exit_code, test_name,
> -			      diagnostic ? "%s" : NULL, diagnostic);
> +	if (diagnostic)
> +		ksft_test_result_code(t->exit_code, test_name, "%s", diagnostic);
> +	else
> +		ksft_test_result_code(t->exit_code, test_name, NULL);

but this diff is not doing that because it is based on a tree that has
caed8eba2215; instead, it appears to be a completely identical
transformation?

Cheers,
Nathan

>  	free(test_name);
>  }
>  
> 
> base-commit: 18daea77cca626f590fb140fc11e3a43c5d41354
> prerequisite-patch-id: b901ece2a5b78503e2fb5480f20e304d36a0ea27
> -- 
> 2.45.0
>