linux-kernel - Re: [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo keyword for switch/case use

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Message-ID: <bc1d19db30ce5ccbbb936144b0f28518a37e8a6c.camel@perches.com>
Date:   Thu, 01 Aug 2019 00:52:06 -0700
From:   Joe Perches <joe@...ches.com>
To:     hpa@...or.com, Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, Pavel Machek <pavel@....cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "Gustavo A . R . Silva" <gustavo@...eddedor.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Shawn Landden <shawn@....icu>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo
 keyword for switch/case use

On Wed, 2019-07-31 at 23:10 -0700, hpa@...or.com wrote:
> On July 31, 2019 4:55:47 PM PDT, Miguel Ojeda <miguel.ojeda.sandonis@...il.com> wrote:
> > On Wed, Jul 31, 2019 at 11:01 PM <hpa@...or.com> wrote:
> > > The standard is moving toward adding this as an attribute with the
> > [[fallthrough]] syntax; it is in C++17, not sure when it will be in C
> > be if it isn't already.
> > 
> > Not yet, but it seems to be coming:
> > 
> >  http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2268.pdf
> > 
> > However, even if C2x gets it, it will be quite a while until the GCC
> > minimum version gets bumped up to that, so...
> > 
> > Cheers,
> > Miguel
> 
> The point was that we should plan ahead in whatever we end up doing.

Using a local keyword will allow any compiler to work successfully.

It's pretty simple to modify this to something like

#define fallback [[fallback]]