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Date:   Thu, 1 Aug 2019 14:24:29 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     hpa@zytor.com
Cc:     Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Joe Perches <joe@perches.com>, Pavel Machek <pavel@ucw.cz>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Borislav Petkov <bp@alien8.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "Gustavo A . R . Silva" <gustavo@embeddedor.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Kan Liang <kan.liang@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Shawn Landden <shawn@git.icu>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo
 keyword for switch/case use
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On Wed, Jul 31, 2019 at 11:10:36PM -0700, hpa@zytor.com wrote:
> On July 31, 2019 4:55:47 PM PDT, Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote:
> >On Wed, Jul 31, 2019 at 11:01 PM <hpa@zytor.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.

By reserving 'fallthrough' as a keyword we do exactly that. We can then
define it to whatever the compiler/tool at hand requires.

Once GCC gains support for that [[attribute]] nonsense, we can detector
that and use that over the __attribute__(())

[ Also the Cxx attribute syntax is an abomination -- just a lesser one
than reading actual comments :-) ]