linux-kernel - Re: [PATCH v6 2/2] scripts: checkpatch: check unused parameters for function-like macro

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Date: Fri, 26 Apr 2024 17:54:00 +0800
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org, linux-doc@...r.kernel.org, 
	workflows@...r.kernel.org, joe@...ches.com
Cc: apw@...onical.com, broonie@...nel.org, chenhuacai@...ngson.cn, 
	chris@...kel.net, corbet@....net, dwaipayanray1@...il.com, 
	herbert@...dor.apana.org.au, linux-kernel@...r.kernel.org, linux@...ck-us.net, 
	lukas.bulwahn@...il.com, mac.xxn@...look.com, sfr@...b.auug.org.au, 
	v-songbaohua@...o.com, Max Filippov <jcmvbkbc@...il.com>, 
	Jeff Johnson <quic_jjohnson@...cinc.com>, Charlemagne Lasse <charlemagnelasse@...il.com>
Subject: Re: [PATCH v6 2/2] scripts: checkpatch: check unused parameters for
 function-like macro

Hi Joe,
any further comment for this ? May this patch get your reviewed / acked?

On Thu, Apr 4, 2024 at 6:43 AM Barry Song <21cnbao@...il.com> wrote:
>
> From: Xining Xu <mac.xxn@...look.com>
>
> If function-like macros do not utilize a parameter, it might result in a
> build warning.  In our coding style guidelines, we advocate for utilizing
> static inline functions to replace such macros.  This patch verifies
> compliance with the new rule.
>
> For a macro such as the one below,
>
>  #define test(a) do { } while (0)
>
> The test result is as follows.
>
>  WARNING: Argument 'a' is not used in function-like macro
>  #21: FILE: mm/init-mm.c:20:
>  +#define test(a) do { } while (0)
>
>  total: 0 errors, 1 warnings, 8 lines checked
>
> Signed-off-by: Xining Xu <mac.xxn@...look.com>
> Tested-by: Barry Song <v-songbaohua@...o.com>
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
> Cc: Chris Zankel <chris@...kel.net>
> Cc: Huacai Chen <chenhuacai@...ngson.cn>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Andy Whitcroft <apw@...onical.com>
> Cc: Dwaipayan Ray <dwaipayanray1@...il.com>
> Cc: Joe Perches <joe@...ches.com>
> Cc: Jonathan Corbet <corbet@....net>
> Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>
> Cc: Max Filippov <jcmvbkbc@...il.com>
> Cc: Jeff Johnson <quic_jjohnson@...cinc.com>
> Cc: Charlemagne Lasse <charlemagnelasse@...il.com>
> ---
>  Documentation/dev-tools/checkpatch.rst | 14 ++++++++++++++
>  scripts/checkpatch.pl                  |  6 ++++++
>  2 files changed, 20 insertions(+)
>
> diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
> index 127968995847..a9fac978a525 100644
> --- a/Documentation/dev-tools/checkpatch.rst
> +++ b/Documentation/dev-tools/checkpatch.rst
> @@ -906,6 +906,20 @@ Macros, Attributes and Symbols
>
>      See: https://lore.kernel.org/lkml/1399671106.2912.21.camel@joe-AO725/
>
> +  **MACRO_ARG_UNUSED**
> +    If function-like macros do not utilize a parameter, it might result
> +    in a build warning. We advocate for utilizing static inline functions
> +    to replace such macros.
> +    For example, for a macro such as the one below::
> +
> +      #define test(a) do { } while (0)
> +
> +    there would be a warning like below::
> +
> +      WARNING: Argument 'a' is not used in function-like macro.
> +
> +    See: https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl
> +
>    **SINGLE_STATEMENT_DO_WHILE_MACRO**
>      For the multi-statement macros, it is necessary to use the do-while
>      loop to avoid unpredictable code paths. The do-while loop helps to
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 9c4c4a61bc83..9895d7e38a9f 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6040,6 +6040,12 @@ sub process {
>                                         CHK("MACRO_ARG_PRECEDENCE",
>                                             "Macro argument '$arg' may be better as '($arg)' to avoid precedence issues\n" . "$herectx");
>                                 }
> +
> +# check if this is an unused argument
> +                               if ($define_stmt !~ /\b$arg\b/) {
> +                                       WARN("MACRO_ARG_UNUSED",
> +                                               "Argument '$arg' is not used in function-like macro\n" . "$herectx");
> +                               }
>                         }
>
>  # check for macros with flow control, but without ## concatenation
> --
> 2.34.1
>

Thanks
Barry