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

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Date:   Tue, 18 Jun 2019 02:30:35 -0700
From:   Joe Perches <joe@...ches.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Shawn Landden <shawn@....icu>, 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 Tue, 2019-06-18 at 09:34 +0200, Pavel Machek wrote:
> On Mon 2019-06-17 09:25:56, Joe Perches wrote:
> > 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.
> 
> We are not userland, and we control whole codebase. These rules don't
> apply.

except include/uapi where some static inline switch might

> We can use unprefixed identifier and fix up any problems... I don't
> expect too many.

but there aren't any existing uses there.