Re: [PATCH 2/2] Compiler Attributes: auxdisplay: panel: use __fallthrough

From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
To: Joe Perches <joe@perches.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Dan <dan.carpenter@oracle.com>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Steven Rostedt <rostedt@goodmis.org>,
	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
	Olof Johansson <olof@lxom.net>,
	Konstantin Ryabitsev <konstantin@linuxfoundation.org>,
	David Miller <davem@davemloft.net>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Kees Cook <keescook@chromium.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>,
	Paul Lawrence <paullawrence@google.com>,
	Sandipan Das <sandipan@linux.vnet.ibm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Will Deacon <will.deacon@arm.com>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Paul Burton <paul.burton@mips.com>,
	David Rientjes <rientjes@google.com>, Willy Tarreau <w@1wt.eu>,
	Martin Sebor <msebor@gmail.com>,
	Christopher Li <sparse@chrisli.org>,
	Jonathan Corbet <corbet@lwn.net>, "Ted Ts'o" <tytso@mit.edu>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Arnd Bergmann <arnd@arndb.de>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Stefan Agner <stefan@agner.ch>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	Ext4 Developers List <linux-ext4@vger.kernel.org>,
	linux-sparse@vger.kernel.org, linux-kbuild@vger.kernel.org
Subject: Re: [PATCH 2/2] Compiler Attributes: auxdisplay: panel: use __fallthrough
Date: Mon, 22 Oct 2018 11:51:59 +0200	[thread overview]
Message-ID: <CANiq72=Eo-c7M1g1gmE0kXNpxe4vkOBT54n9gMB9UBSEfzTMAw@mail.gmail.com> (raw)
In-Reply-To: <f46baa5bb0e3373c89d09b6e0d15170902e5f55c.camel@perches.com>

On Sun, Oct 21, 2018 at 8:11 PM Joe Perches <joe@perches.com> wrote:
>
> On Sun, 2018-10-21 at 19:14 +0200, Miguel Ojeda wrote:
> > Let gcc know these cases are meant to fall through to the next label
> > by annotating them with the new __fallthrough statement attribute;
> > and remove the comment since it conveys the same information
> > (which was also parsed by gcc to suppress the warning).
>
> Instead of many individual conversion patches,
> perhaps a script to do all the conversions at once.

Note that this was only an example of the attribute (some people asked
for an example when introducing another one, so I preemptively did it
for this one).

Doing the conversion (and how :-) I left it for afterwards, if people
agree with the attribute.

>
> Maybe:
>
> pattern='(?:\/\*\s*fall(?:\s*|\s*\-\s*)thr(?:u|ough)\s*\*\/|\/\/\s*fall\s*thr(?:u|ough)\s*$)'
> git grep -P -i --name-only "$pattern" -- '*.[ch]' |
>     xargs perl -p -i -e "s/$pattern/__fallthrough;/gi"

By the way, I checked first if coccinelle could match input comments,
but it doesn't, according to Julia. I am also thinking whether a
compiler plugin could easily do this, but I don't have my hopes high
given these are comments...

Also, regardless of how it is done, the patches need to be sent
individually to maintainers, no? I have a vague memory that big &
automated conversions were a bit frozen upon in the kernel. Greg...?

Cheers,
Miguel