linux-kernel - Re: [PATCH v5 2/2] scripts: checkpatch: check unused parameters for function-like macro

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Message-ID: <f5bb12d8602a03d28b2a8aeaffd8f74f001d692d.camel@perches.com>
Date: Sun, 31 Mar 2024 19:37:09 -0700
From: Joe Perches <joe@...ches.com>
To: Barry Song <21cnbao@...il.com>, akpm@...ux-foundation.org, 
	linux-doc@...r.kernel.org, workflows@...r.kernel.org
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 v5 2/2] scripts: checkpatch: check unused parameters for
 function-like macro

On Mon, 2024-04-01 at 14:21 +1300, Barry Song 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.
> 
>  ERROR: Parameter 'a' is not used in function-like macro, please use static
>  inline instead
>  #21: FILE: mm/init-mm.c:20:
>  +#define test(a) do { } while (0)

This is no longer true.
Please update the ERROR->WARN and message as below

Ideally, this would have an update to
Documentation/dev-tools/checkpatch.rst

to describe the new --verbose message type

> diff --git 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");
> +				}