linux-kernel - Re: [PATCH] signal: Mark expected switch fall-throughs

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Message-ID: <87y3aylpn5.fsf@concordia.ellerman.id.au>
Date:   Tue, 16 Oct 2018 11:08:14 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        ebiederm@...ssion.com
Subject: Re: [PATCH] signal: Mark expected switch fall-throughs

[ Cc += ebiederm@...ssion.com ]

"Gustavo A. R. Silva" <gustavo@...eddedor.com> writes:
> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> where we are expecting to fall through.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  include/linux/signal.h | 6 ++++++
>  1 file changed, 6 insertions(+)

These all look correct to me.

Reviewed-by: Michael Ellerman <mpe@...erman.id.au>

> diff --git a/include/linux/signal.h b/include/linux/signal.h
> index 200ed96..f428e86 100644
> --- a/include/linux/signal.h
> +++ b/include/linux/signal.h
> @@ -129,9 +129,11 @@ static inline void name(sigset_t *r, const sigset_t *a, const sigset_t *b) \
>  		b3 = b->sig[3]; b2 = b->sig[2];				\
>  		r->sig[3] = op(a3, b3);					\
>  		r->sig[2] = op(a2, b2);					\
> +		/* fall through */					\
>  	case 2:								\
>  		a1 = a->sig[1]; b1 = b->sig[1];				\
>  		r->sig[1] = op(a1, b1);					\
> +		/* fall through */					\
>  	case 1:								\
>  		a0 = a->sig[0]; b0 = b->sig[0];				\
>  		r->sig[0] = op(a0, b0);					\
> @@ -161,7 +163,9 @@ static inline void name(sigset_t *set)					\
>  	switch (_NSIG_WORDS) {						\
>  	case 4:	set->sig[3] = op(set->sig[3]);				\
>  		set->sig[2] = op(set->sig[2]);				\
> +		/* fall through */					\
>  	case 2:	set->sig[1] = op(set->sig[1]);				\
> +		/* fall through */					\
>  	case 1:	set->sig[0] = op(set->sig[0]);				\
>  		    break;						\
>  	default:							\
> @@ -182,6 +186,7 @@ static inline void sigemptyset(sigset_t *set)
>  		memset(set, 0, sizeof(sigset_t));
>  		break;
>  	case 2: set->sig[1] = 0;
> +		/* fall through */
>  	case 1:	set->sig[0] = 0;
>  		break;
>  	}
> @@ -194,6 +199,7 @@ static inline void sigfillset(sigset_t *set)
>  		memset(set, -1, sizeof(sigset_t));
>  		break;
>  	case 2: set->sig[1] = -1;
> +		/* fall through */
>  	case 1:	set->sig[0] = -1;
>  		break;
>  	}

I think _NSIG_WORDS is always constant. So these last two seem like they
could just be replaced with memset() and a modern compiler would do the
right thing.

cheers