From: Kees Cook <keescook@chromium.org>
To: Joe Perches <joe@perches.com>
Cc: hpa@zytor.com, Peter Zijlstra <peterz@infradead.org>,
Pavel Machek <pavel@ucw.cz>,
Linus Torvalds <torvalds@linux-foundation.org>,
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
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>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo keyword for switch/case use
Date: Thu, 15 Aug 2019 11:15:53 -0700 [thread overview]
Message-ID: <201908151049.809B9AFBA9@keescook> (raw)
In-Reply-To: <201907311301.EC1D84F@keescook>
On Wed, Jul 31, 2019 at 01:02:07PM -0700, Kees Cook wrote:
> On Wed, Jul 31, 2019 at 08:48:32PM +0200, Peter Zijlstra wrote:
> > On Wed, Jul 31, 2019 at 11:24:36AM -0700, hpa@zytor.com wrote:
> > > >> > +/*
> > > >> > + * 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#Statement-Attributes
> > > >> > + */
> > > >> > +#if __has_attribute(__fallthrough__)
> > > >> > +# define fallthrough __attribute__((__fallthrough__))
> > > >> > +#else
> > > >> > +# define fallthrough do {} while (0) /* fallthrough */
> > > >> > +#endif
> > > >> > +
> >
> > > If the comments are stripped, how would the compiler see them to be
> > > able to issue a warning? I would guess that it is retained or replaced
> > > with some other magic token.
> >
> > Everything that has the warning (GCC-7+/CLANG-9) has that attribute.
>
> I'd like to make sure we don't regress Coverity most of all. If the
> recent updates to the Coverity scanner include support for the attribute
> now, then I'm all for it. :)
I want to recant my position on Coverity coverage being a requirement
here. While I was originally concerned about suddenly adding thousands
more warnings to Coverity scans (if it doesn't support the flag --
I should know soon), it's been made clear to me we're now at the point
where this is about to happen for Clang instead (since _it_ doesn't
support the comment-style marking and never will but is about to gain
C support[1] for the detection -- it only had C++ before).
With that out of the way, yes, let's do a mass conversion. As mentioned
before, I think "fallthrough;" should be used here (to match "break;").
Let's fork the C language. :)
-Kees
[1] https://reviews.llvm.org/D64838
--
Kees Cook
next prev parent reply other threads:[~2019-08-15 18:15 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-31 5:04 [PATCH] net: sctp: Rename fallthrough label to unhandled Joe Perches
2019-07-31 5:35 ` [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo keyword for switch/case use Joe Perches
2019-07-31 9:02 ` Peter Zijlstra
2019-07-31 9:34 ` Joe Perches
2019-07-31 17:14 ` Pavel Machek
2019-07-31 17:51 ` Joe Perches
2019-07-31 18:24 ` hpa
2019-07-31 18:48 ` Peter Zijlstra
2019-07-31 20:02 ` Kees Cook
2019-07-31 20:59 ` Miguel Ojeda
2019-07-31 22:07 ` Joe Perches
2019-08-01 0:00 ` Miguel Ojeda
2019-08-01 12:25 ` Peter Zijlstra
2019-08-15 18:15 ` Kees Cook [this message]
2019-08-15 22:31 ` Kees Cook
2019-09-16 22:19 ` treewide replacement of fallthrough comments with "fallthrough" macro (was Re: [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo keyword for switch/case use) Kees Cook
2019-09-17 22:26 ` Joe Perches
2019-09-17 23:38 ` Kees Cook
2019-07-31 21:01 ` [RFC PATCH] compiler_attributes.h: Add 'fallthrough' pseudo keyword for switch/case use hpa
2019-07-31 23:55 ` Miguel Ojeda
2019-08-01 6:10 ` hpa
2019-08-01 7:52 ` Joe Perches
2019-08-01 12:24 ` Peter Zijlstra
2019-08-01 20:09 ` hpa
2019-08-01 20:26 ` Miguel Ojeda
2019-08-01 20:47 ` Joe Perches
2019-08-02 11:00 ` Neil Horman
2019-08-02 12:34 ` Pavel Machek
2019-08-02 16:09 ` Kees Cook
2019-08-02 16:16 ` Joe Perches
2019-08-04 18:01 ` Joe Perches
2019-08-04 18:09 ` Linus Torvalds
2019-08-04 19:38 ` Miguel Ojeda
2019-08-05 0:39 ` Joe Perches
2019-08-05 1:18 ` Nathan Chancellor
2019-08-05 2:01 ` Joe Perches
2019-07-31 11:19 ` [PATCH] net: sctp: Rename fallthrough label to unhandled Neil Horman
2019-07-31 11:32 ` Joe Perches
2019-07-31 12:16 ` Neil Horman
2019-07-31 16:35 ` Joe Perches
2019-07-31 20:58 ` Neil Horman
2019-07-31 22:23 ` Joe Perches
2019-08-01 10:50 ` Neil Horman
2019-08-01 17:42 ` Joe Perches
2019-08-01 20:48 ` Neil Horman
2019-08-05 11:49 ` David Laight
2019-08-02 17:47 ` Joe Perches
2019-08-02 23:19 ` David Miller
2019-08-02 23:26 ` Joe Perches
2019-08-03 18:01 ` Joe Perches
2019-08-04 19:26 ` Neil Horman
2019-08-02 17:50 ` Neil Horman
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