linux-kernel - Re: [PATCH] Use fall-through attribute rather than magic comments

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Date:   Mon, 17 Jun 2019 09:25:56 -0700
From:   Joe Perches <joe@...ches.com>
To:     Pavel Machek <pavel@....cz>, Shawn Landden <shawn@....icu>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A . R . Silva" <gustavo@...eddedor.com>,
        Andy Whitcroft <apw@...onical.com>
Subject: Re: [PATCH] Use fall-through attribute rather than magic comments

On Mon, 2019-06-17 at 17:56 +0200, Pavel Machek wrote:
> Hi!
> 
> > +/*
> > + *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wimplicit-fallthrough
> > + *   gcc: https://developers.redhat.com/blog/2017/03/10/wimplicit-fallthrough-in-gcc-7/
> > + */
> > +#if __has_attribute(__fallthrough__)
> > +# define __fallthrough                    __attribute__((__fallthrough__))
> > +#else
> > +# define __fallthrough
> > +#endif
> 
> Is it good idea to add the __'s ? They look kind of ugly. 

Dunno.

I agree it's kind of ugly, but it should always work.

I think the generic problem is introducing a new unprefixed
reserved identifier.  Underscored identifiers are reserved.

There is already a fallthrough: label used in kernel sources
in net/sctp/sm_make_chunk.c that should probably be changed.