Re: [PATCH 1/2] Compiler Attributes: add support for __fallthrough (gcc >= 7.1)

From: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
	dan.carpenter@oracle.com, "Theodore Ts'o" <tytso@mit.edu>,
	Greg KH <gregkh@linuxfoundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	adilger.kernel@dilger.ca,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Michal Marek <michal.lkml@markovi.net>,
	rostedt@goodmis.org, mchehab+samsung@kernel.org, olof@lxom.net,
	Konstantin Ryabitsev <konstantin@linuxfoundation.org>,
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	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Subject: Re: [PATCH 1/2] Compiler Attributes: add support for __fallthrough (gcc >= 7.1)
Date: Mon, 22 Oct 2018 20:13:46 +0200	[thread overview]
Message-ID: <9c52827b-4783-8f39-9030-a166d5436f05@petrovitsch.priv.at> (raw)
In-Reply-To: <CAKwvOdnWkPi_2UJ7VKYZ6cuWi+BDgpEUf+tcrfZLUYawbm+grw@mail.gmail.com>

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Hi all!

On 22/10/18 19:54, Nick Desaulniers wrote:
> On Mon, Oct 22, 2018 at 10:50 AM Bernd Petrovitsch
> <bernd@petrovitsch.priv.at> wrote:
[...]
>> PS: clang++ errors with "fallthrough annotation in unreachable code" if
>>     [[fallthrough]] is after an assert(). clang-devs there, please, the
>>     fallthrough doesn't really generated code (I hope;-).
[...]
> Can you send me a link to a simple reproducer in godbolt (godbolt.org)
> and we'll take a look?

Does https://godbolt.org/z/2Y4zIo do it - I'm a godbolt-newbie?

For
----  snip  ----
#include <cassert>

int main(void)
{
  switch (1) {
  default:
    assert(0);
    [[fallthrough]];
  case 1:
    ;
  }
  return 0;
}
----  snip  ----
Just "clang++ -Wimplicit-fallthrough -Werror" it .....

MfG,
	Bernd
-- 
"I dislike type abstraction if it has no real reason. And saving
on typing is not a good reason - if your typing speed is the main
issue when you're coding, you're doing something seriously wrong."
    - Linus Torvalds

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