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From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date: Mon, 22 Oct 2018 22:59:16 +0200
Message-ID: <CANiq72kUJOSrR=h2=2jXfkBPLrR=DrN8X4OoKOqAte4sMLxkdQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] Compiler Attributes: add support for __fallthrough
 (gcc >= 7.1)
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        "Ted Ts'o" <tytso@mit.edu>, Greg KH <gregkh@linuxfoundation.org>,
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        Dan <dan.carpenter@oracle.com>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Michal Marek <michal.lkml@markovi.net>,
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        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
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Sender: linux-ext4-owner@vger.kernel.org

On Mon, Oct 22, 2018 at 7:17 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Mon, Oct 22, 2018 at 2:43 AM Miguel Ojeda
> <miguel.ojeda.sandonis@gmail.com> wrote:
> >
> > On Mon, Oct 22, 2018 at 11:41 AM Miguel Ojeda
> > <miguel.ojeda.sandonis@gmail.com> wrote:
> > >
> > >   * clang does *not* support the attribute in C.
> >
> > ...nor the warning at all, by the way (which is why this is OK).
> >
> > Cheers,
> > Miguel
>
> Oh? We're going through and annotating all of Android's C++ source
> right now with it.
> https://clang.llvm.org/docs/DiagnosticsReference.html#wimplicit-fallthrough
>

Sure, but I am talking about the C mode only. Please read the previous
messages in the thread :-)

> Though it looks like the attribute syntax I like from GCC is not yet
> supported in Clang.

Indeed, that is what I explained in the last message.

> https://bugs.llvm.org/show_bug.cgi?id=37135
> https://github.com/ClangBuiltLinux/linux/issues/235
> I'll take a look at adding support.
>
> So Kees sent me this embarrassing example:
> https://godbolt.org/z/gV_c9_
> (try changing the language from C++ to C; it works)!  That's embarrassing!

Yup, that is what I have been testing yesterday -- see the linked
thread in the commit message for the summary of the results.

> https://bugs.llvm.org/show_bug.cgi?id=39382
> https://github.com/ClangBuiltLinux/linux/issues/236
> Will get these both fixed up.

Cheers,
Miguel