linux-kernel - Re: [PATCH] checksyscalls: ignore -Wunused-macros

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Date:   Mon, 25 Apr 2022 15:17:29 +0900
From:   Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] checksyscalls: ignore -Wunused-macros

Hi Nathan,

Thanks for the comments!

On Mon. 25 Apr 2022 at 07:17, Nathan Chancellor <nathan@...nel.org> wrote:
> Hi Vincent,
>
> On Sat, Apr 23, 2022 at 12:17:25AM +0900, Vincent Mailhol wrote:
> > The macros defined in this file are for testing only and are purposely
> > not used. When compiled with W=2, both gcc and clang yield some
> > -Wunused-macros warnings. Ignore them.
> >
> > Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
>
> The change itself looks fine but a couple of comments:
>
> 1. Nick and I do not pick up patches, we rely on others to do so.
>    Additionally, this is not really something within our domain, despite
>    what get_maintainer.pl might say. This change should be sent to
>    either
>
>    Masahiro Yamada <masahiroy@...nel.org>
>    linux-kbuild@...r.kernel.org
>
>    or
>
>    Andrew Morton <akpm@...ux-foundation.org>
>
>    so that it can be applied by one of them.

Ack. As you pointed out, I indeed just followed get_maintainer.pl.
I will resend a v2 to the people you pointed out (and exclude you).

> 2. I am not sure that silencing warnings from W=2 is that useful, as
>    they are unlikely to be real issues. Not to discourage you by any
>    means but it might be more useful to focus on cleaning up warnings
>    from W=1 and getting those promoted to regular build warnings.

Normally I agree, but there is one reason to fix this W=2: this
warning appears when building other files.

Example:
| $ make W=2 drivers/net/dummy.o
|   CALL    scripts/checksyscalls.sh
| <stdin>:21: warning: macro "__IGNORE_stat64" is not used [-Wunused-macros]
| <stdin>:22: warning: macro "__IGNORE_lstat64" is not used [-Wunused-macros]
| <stdin>:75: warning: macro "__IGNORE_llseek" is not used [-Wunused-macros]
| <stdin>:159: warning: macro "__IGNORE_madvise1" is not used [-Wunused-macros]
(rest of the output redacted).

When I run W=2, I want to only see the warnings of the file I am
working on. So I find it useful to fix the W=2 warnings which
show up when building other files to not get spammed by
irrelevant issues and to simplify the triage.

My initial message lacked the rationale. I will add additional
explanations in the v2 of this patch.

Yours sincerely,
Vincent Mailhol