linux-kernel - Re: [PATCH v2 07/10] selftests/nolibc: avoid unused arguments warnings

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Date:   Tue,  1 Aug 2023 18:15:08 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     linux@...ssschuh.net
Cc:     falcon@...ylab.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, shuah@...nel.org,
        tanyuan@...ylab.org, w@....eu
Subject: Re: [PATCH v2 07/10] selftests/nolibc: avoid unused arguments warnings

Hi, Thomas

> On 2023-08-01 10:07:28+0200, Willy Tarreau wrote:
> > On Tue, Aug 01, 2023 at 07:30:14AM +0200, Thomas Weißschuh wrote:
> > > This warnings will be enabled later so avoid triggering it.
> > > 
> > > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > > ---
> > >  tools/testing/selftests/nolibc/nolibc-test.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
> > > index 53a3773c7790..cb17cccd0bc7 100644
> > > --- a/tools/testing/selftests/nolibc/nolibc-test.c
> > > +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> > > @@ -1089,7 +1089,8 @@ static int smash_stack(void)
> > >  	return 1;
> > >  }
> > >  
> > > -static int run_protection(int min, int max)
> > > +static int run_protection(int __attribute__((unused)) min,
> > > +			  int __attribute__((unused)) max)
> > 
> > This one is used to silence -Wunused-parameter I guess.
> 
> Yep.
> 
> > It's one of
> > the rare warnings that I find totally useless in field, because it's
> > simply against the principle of using function pointers with different
> > functions having the same interface but different implementations. As
> > your code evolves you end up with unused on absolutely *all* of the
> > arguments of *all* such functions, which makes them a real pain to add
> > and tends to encourage poor practices such as excessive code reuse just
> > by laziness or boredom. BTW it's one of those that are already disabled
> > in the kernel and we could very well do the same here.
> 
> It's indeed unfortunate.
> 
> As long as we don't have too many of them I would prefer to keep the
> explicit annotations. While they are ugly we then can still reap the
> positive aspects of the warning.
> 
> This is where -std=c89 bites us. With extensions (or C2X) we could also
> just leave off the argument name to mark it as unused:
>     run_protection(int, int)

what about further simply ignore the arguments like we did for main(void)?

Thanks,
Zhangjin