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[0/2] Compiler Attributes: __fallthrough

Message ID 20181021171414.22674-1-miguel.ojeda.sandonis@gmail.com (mailing list archive)
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Series Compiler Attributes: __fallthrough | expand

Message

Miguel Ojeda Oct. 21, 2018, 5:14 p.m. UTC 
These are two patches are meant to go on top of the rest of the compiler
attributes series on:

  https://github.com/ojeda/linux/tree/compiler-attributes

which will be sent to Greg for the next merge window.

Please review them and let me know! (specially if someone is against
__fallthrough for some reason :-).

The first patch introduces the attribute and gives the rationale.
The second patch is an example of usage.

This was started in the following thread:

  https://lore.kernel.org/lkml/20181017062255.oiu44y4zuuwilan3@mwanda/

Cheers,
Miguel

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Olof Johansson <olof@lxom.net>
Cc: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Lawrence <paullawrence@google.com>
Cc: Sandipan Das <sandipan@linux.vnet.ibm.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Martin Sebor <msebor@gmail.com>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Joe Perches <joe@perches.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-ext4@vger.kernel.org
Cc: linux-sparse@vger.kernel.org
Cc: linux-kbuild@vger.kernel.org

Miguel Ojeda (2):
  Compiler Attributes: add support for __fallthrough (gcc >= 7.1)
  Compiler Attributes: auxdisplay: panel: use __fallthrough

 drivers/auxdisplay/panel.c          |  6 +++---
 include/linux/compiler_attributes.h | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

Comments

Greg Kroah-Hartman Oct. 21, 2018, 6:29 p.m. UTC | #1 
On Sun, Oct 21, 2018 at 07:14:12PM +0200, Miguel Ojeda wrote:
> These are two patches are meant to go on top of the rest of the compiler
> attributes series on:
> 
>   https://github.com/ojeda/linux/tree/compiler-attributes
> 
> which will be sent to Greg for the next merge window.
> 
> Please review them and let me know! (specially if someone is against
> __fallthrough for some reason :-).

Will this work with all of the static tools that are currently looking
for the comment instead?  I know coverity handles that, what about
others?

thanks,

greg k-h
Joe Perches Oct. 21, 2018, 6:52 p.m. UTC | #2 
On Sun, 2018-10-21 at 19:29 +0100, Greg Kroah-Hartman wrote:i
> On Sun, Oct 21, 2018 at 07:14:12PM +0200, Miguel Ojeda wrote:
> > These are two patches are meant to go on top of the rest of the compiler
> > attributes series on:
> > 
> >   https://github.com/ojeda/linux/tree/compiler-attributes
> > 
> > which will be sent to Greg for the next merge window.
> > 
> > Please review them and let me know! (specially if someone is against
> > __fallthrough for some reason :-).
> 
> Will this work with all of the static tools that are currently looking
> for the comment instead?

Does anyone have a list of the static tools that
use comment style fallthrough notations?

> I know coverity handles that, what about others?

No doubt tool updates would be useful.
Dan Carpenter Oct. 22, 2018, 5:27 a.m. UTC | #3 
On Sun, Oct 21, 2018 at 11:52:21AM -0700, Joe Perches wrote:
> On Sun, 2018-10-21 at 19:29 +0100, Greg Kroah-Hartman wrote:i
> > On Sun, Oct 21, 2018 at 07:14:12PM +0200, Miguel Ojeda wrote:
> > > These are two patches are meant to go on top of the rest of the compiler
> > > attributes series on:
> > > 
> > >   https://github.com/ojeda/linux/tree/compiler-attributes
> > > 
> > > which will be sent to Greg for the next merge window.
> > > 
> > > Please review them and let me know! (specially if someone is against
> > > __fallthrough for some reason :-).
> > 
> > Will this work with all of the static tools that are currently looking
> > for the comment instead?
> 
> Does anyone have a list of the static tools that
> use comment style fallthrough notations?
> 

It would only be CPPcheck I think.

regards,
dan carpenter
Miguel Ojeda Oct. 22, 2018, 9:48 a.m. UTC | #4 
On Sun, Oct 21, 2018 at 8:29 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Sun, Oct 21, 2018 at 07:14:12PM +0200, Miguel Ojeda wrote:
> > These are two patches are meant to go on top of the rest of the compiler
> > attributes series on:
> >
> >   https://github.com/ojeda/linux/tree/compiler-attributes
> >
> > which will be sent to Greg for the next merge window.
> >
> > Please review them and let me know! (specially if someone is against
> > __fallthrough for some reason :-).
>
> Will this work with all of the static tools that are currently looking
> for the comment instead?  I know coverity handles that, what about
> others?

Thank you Greg, good question. I will try to keep all the information
we can get about the tools in the commit message.

I will also contact the different tools about this.

Cheers,
Miguel
Nick Desaulniers Oct. 22, 2018, 4:54 p.m. UTC | #5 
On Mon, Oct 22, 2018 at 2:48 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> On Sun, Oct 21, 2018 at 8:29 PM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > Will this work with all of the static tools that are currently looking
> > for the comment instead?  I know coverity handles that, what about
> > others?
>
> I will also contact the different tools about this.

Let's contact the authors of these tools if they don't parse the
attribute.  I prefer to have the attributes rather than specifically
formatted comments.

I do think this may be tricky to provide backwards support for though;
Miguel, do you have info on which versions of GCC support comments vs
attribute?
Miguel Ojeda Oct. 22, 2018, 9:23 p.m. UTC | #6 
On Mon, Oct 22, 2018 at 6:54 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Mon, Oct 22, 2018 at 2:48 AM Miguel Ojeda
> <miguel.ojeda.sandonis@gmail.com> wrote:
> >
> > On Sun, Oct 21, 2018 at 8:29 PM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > >
> > > Will this work with all of the static tools that are currently looking
> > > for the comment instead?  I know coverity handles that, what about
> > > others?
> >
> > I will also contact the different tools about this.
>
> Let's contact the authors of these tools if they don't parse the
> attribute.  I prefer to have the attributes rather than specifically
> formatted comments.

Sorry, not sure what you mean -- isn't that what I said? Greg was
asking whether tools would support the attribute equally well compared
to the comment parsing; not the comments.

>
> I do think this may be tricky to provide backwards support for though;
> Miguel, do you have info on which versions of GCC support comments vs
> attribute?

It is in the commit message:

    """
    In C mode, GCC supports the __fallthrough__ attribute since 7.1,
    the same time the warning and the comment parsing were introduced.
    """

Cheers,
Miguel
Dan Carpenter Oct. 23, 2018, 5:43 a.m. UTC | #7 
On Mon, Oct 22, 2018 at 09:54:27AM -0700, Nick Desaulniers wrote:
> On Mon, Oct 22, 2018 at 2:48 AM Miguel Ojeda
> <miguel.ojeda.sandonis@gmail.com> wrote:
> >
> > On Sun, Oct 21, 2018 at 8:29 PM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > >
> > > Will this work with all of the static tools that are currently looking
> > > for the comment instead?  I know coverity handles that, what about
> > > others?
> >
> > I will also contact the different tools about this.
> 
> Let's contact the authors of these tools if they don't parse the
> attribute.  I prefer to have the attributes rather than specifically
> formatted comments.
> 
> I do think this may be tricky to provide backwards support for though;
> Miguel, do you have info on which versions of GCC support comments vs
> attribute?

None.  GCC 7.1 added support for the warning, the comment parsing and
the attribute so it's fine.

The only thing that we know for sure is an issue is Eclipse.

We need to test Coverity but it should work in theory.  And we don't
know about CPPcheck.

regards,
dan carpenter