linux-kernel - Re: [PATCH] Makefile: Convert -Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang

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Message-ID: <514fb156-7d81-a812-510a-7f252c27e79e@petrovitsch.priv.at>
Date:   Sun, 11 Aug 2019 08:50:29 +0200
From:   Bernd Petrovitsch <bernd@...rovitsch.priv.at>
To:     Nathan Chancellor <natechancellor@...il.com>,
        Joe Perches <joe@...ches.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] Makefile: Convert -Wimplicit-fallthrough=3 to just
 -Wimplicit-fallthrough for clang

On 11/08/2019 05:17, Nathan Chancellor wrote:
> On Sat, Aug 10, 2019 at 08:06:05PM -0700, Joe Perches wrote:
>> On Sat, 2019-08-10 at 19:04 -0700, Nathan Chancellor wrote:
>>> On a tangential note, how are you planning on doing the fallthrough
>>> comment to attribute conversion? The reason I ask is clang does not
>>> support the comment annotations, meaning that when Nathan Huckleberry's
>>> patch is applied to clang (which has been accepted [1]), we are going
>>> to get slammed by the warnings. I just ran an x86 defconfig build at
>>> 296d05cb0d3c with his patch applied and I see 27673 instances of this
>>> warning... (mostly coming from some header files so nothing crazy but it
>>> will be super noisy).
>>>
>>> If you have something to share like a script or patch, I'd be happy to
>>> test it locally.
>>>
>>> [1]: https://reviews.llvm.org/D64838
>>
>> Something like this patch:
>>
>> https://lore.kernel.org/patchwork/patch/1108577/
>>
>> Maybe use:
>>
>> #define fallthrough [[fallthrough]]
>>
>> if the compiler supports that notation
>>
> 
> That patch as it stands will work with D64838, as it is adding support
> for the GNU fallthrough attribute.
>
> However, I assume that all of the /* fall through */ comments will need
> to be converted to the attribute macro, was that going to be done with
> Coccinelle or something else?

clang has not problem with the comment - it's just a comment;-)

The #define above works BTW.

MfG,
	Bernd
-- 
Bernd Petrovitsch                  Email : bernd@...rovitsch.priv.at
                     LUGA : http://www.luga.at