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

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Message-ID: <CANiq72kg+duBe_srpcco-P17=3OC2c1ys=rGMVY8Z9FxZ69sdw@mail.gmail.com>
Date:   Thu, 1 Aug 2019 22:26:29 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     "H. Peter Anvin" <hpa@...or.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Joe Perches <joe@...ches.com>, 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 Thu, Aug 1, 2019 at 10:10 PM <hpa@...or.com> wrote:
>
> I'm not disagreeing... I think using a macro makes sense.

It is either a macro or waiting for 5+ years (while we keep using the
comment style) :-)

In case it helps to make one's mind about whether to go for it or not,
I summarized the advantages and a few other details in the patch I
sent in October:

  https://github.com/ojeda/linux/commit/668f011a2706ea555987e263f609a5deba9c7fc4

It would be nice, however, to discuss whether we want __fallthrough or
fallthrough. The former is consistent with the rest of compiler
attributes and makes it clear it is not a keyword, the latter is
consistent with "break", "goto" and "return", as Joe's patch explains.

Cheers,
Miguel