linux-kernel - Re: [PATCH v5 1/8] selftests: Add printf attribute to kselftest prints

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Message-ID: <4h2eu6yhodrujbvem24v7cwal5tnk2agsqulpxwi4myk7n35uq@phbxlajivrpq>
Date:   Thu, 12 Oct 2023 09:32:39 +0200
From:   Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>
To:     Shuah <shuah@...nel.org>
CC:     <ilpo.jarvinen@...ux.intel.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        <linux-kselftest@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/8] selftests: Add printf attribute to kselftest
 prints

On 2023-10-11 at 13:40:48 -0600, Shuah wrote:
>On 10/11/23 02:23, Maciej Wieczor-Retman wrote:
>> Kselftest header defines multiple variadic functions that use printf
>> along with other logic.
>> 
>> There is no format checking for the variadic functions that use
>> printing inside kselftest.h. Because of this the compiler won't
>> be able to catch instances of mismatched printf formats and debugging
>> tests might be more difficult.
>> 
>> Add the common __printf attribute macro to kselftest.h.
>> 
>> Add __printf attribute to every function using formatted printing with
>> variadic arguments.
>> 
>> Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>
>> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
>> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
>> ---
>> Changelog v4:
>> - Fix typo in patch subject. (Reinette)
>> - Add Reinette's reviewed-by tag.
>> 
>
>I still need information on how you found these problems. Please
>add it to change log for each of these patches.

Sure, I'll add notes on methodology to patches 2-8. I understand that
this patch (1/8) message doesn't need that addition since the problems
it exposes are in separate patches.

Or would you like me to also note here more specifically what effect it
has in the rest of the series?

>I am seeing checkpatch warning:
>
>WARNING: Prefer __printf(a, b) over __attribute__((format(printf, a, b)))
>#102: FILE: tools/testing/selftests/kselftest.h:81:
>+#define __printf(a, b)   __attribute__((format(printf, a, b)))

Running checkpatch.pl with --show-types shows the
PREFER_DEFINED_ATTRIBUTE_MACRO is raised. From looking at the error
message in the script it looks like a false positive:
	"Prefer $new over __attribute__(($orig_attr$params))\n"

Please correct me if my train of thought is wrong but I think checkpatch
sees __printf() macro defined and it sees it's raw version
"__attribute__((format(printf, a, b)))" which it wants to replace with
the macro. But since the raw version is found in the define line that is
obviously not possible.

>thanks,
>-- Shuah

-- 
Kind regards
Maciej Wieczór-Retman