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

[John Hubbard <jhubbard@nvidia.com>]

On 5/1/24 8:13 AM, Nathan Chancellor wrote:
> 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?

Apparently not!

> 
>> Fix by passing NULL, instead of "", for the msg argument to
> 
> Because this text is describing what was done in caed8eba2215...

Yes. I took a while between discovering the issue, and posting a fix, I
think that's why.

> 
>> 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@valentinobst.de>
>> Cc: Kees Cook <keescook@chromium.org>
>> Cc: Nick Desaulniers <ndesaulniers@google.com>
>> Cc: Nathan Chancellor <nathan@kernel.org>
>> Cc: Shuah Khan <shuah@kernel.org>
>> Cc: Justin Stitt <justinstitt@google.com>
>> Cc: Bill Wendling <morbo@google.com>
>> Signed-off-by: John Hubbard <jhubbard@nvidia.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?
> 

It's nice to see that someone else had the same fix, anyway. Sorry
about the noise, and yes let's please just drop this one.

thanks,
-- 
John Hubbard
NVIDIA