linux-kernel - Re: [PATCH] signal: fix building with clang

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Message-ID: <CAKwvOdkEuK04iqdrGR1CaHGc-3zCAS+tGnvfN8R0+j728TTPtQ@mail.gmail.com>
Date:   Thu, 7 Mar 2019 10:41:57 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-arch <linux-arch@...r.kernel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Christian Brauner <christian@...uner.io>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        linux-mips@...r.kernel.org
Subject: Re: [PATCH] signal: fix building with clang

On Thu, Mar 7, 2019 at 8:46 AM Oleg Nesterov <oleg@...hat.com> wrote:
>
> On 03/07, Arnd Bergmann wrote:
> >
> > We could use % everywhere,
>
> Yes.
>
> But again, why not simply use the "for (;;)" loops? Why we can't kill the
> supid switch(_NSIG_WORDS) tricks altogether?
>
> Oleg.
>
> --- x/include/linux/signal.h
> +++ x/include/linux/signal.h
> @@ -121,26 +121,9 @@
>  #define _SIG_SET_BINOP(name, op)                                       \
>  static inline void name(sigset_t *r, const sigset_t *a, const sigset_t *b) \
>  {                                                                      \
> -       unsigned long a0, a1, a2, a3, b0, b1, b2, b3;                   \
> -                                                                       \
> -       switch (_NSIG_WORDS) {                                          \
> -       case 4:                                                         \
> -               a3 = a->sig[3]; a2 = a->sig[2];                         \
> -               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);                                 \
> -               break;                                                  \
> -       default:                                                        \
> -               BUILD_BUG();                                            \
> -       }                                                               \
> +       int i;                                                          \
> +       for (i = 0; i < ARRAY_SIZE(r->sig); ++i)                        \
> +               r->sig[i] = op(a->sig[i], b->sig[i]);                   \
>  }
>
>  #define _sig_or(x,y)   ((x) | (y))
>

That looks much cleaner IMO.
-- 
Thanks,
~Nick Desaulniers