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Date:   Wed, 31 Jul 2019 19:14:29 +0200
From:   Pavel Machek <pavel@ucw.cz>
To:     Joe Perches <joe@perches.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Kees Cook <keescook@chromium.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        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>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo
 keyword for switch/case use
Message-ID: <20190731171429.GA24222@amd>
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On Tue 2019-07-30 22:35:18, Joe Perches wrote:
> Reserve the pseudo keyword 'fallthrough' for the ability to convert the
> various case block /* fallthrough */ style comments to appear to be an
> actual reserved word with the same gcc case block missing fallthrough
> warning capability.

Acked-by: Pavel Machek <pavel@ucw.cz>

> +/*
> + * Add the pseudo keyword 'fallthrough' so case statement blocks
> + * must end with any of these keywords:
> + *   break;
> + *   fallthrough;
> + *   goto <label>;
> + *   return [expression];
> + *
> + *  gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#St=
atement-Attributes
> + */
> +#if __has_attribute(__fallthrough__)
> +# define fallthrough                    __attribute__((__fallthrough__))
> +#else
> +# define fallthrough                    do {} while (0)  /* fallthrough =
*/
> +#endif
> +

Will various checkers (and gcc) recognize, that comment in a macro,
and disable the warning accordingly?

Explanation that the comment is "magic" might not be a bad idea.

Thanks,

									Pavel

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