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

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Message-ID: <0c96ff086dc1b92034a8ca19d341f2db16cc802c.camel@perches.com>
Date:   Sat, 10 Aug 2019 20:54:21 -0700
From:   Joe Perches <joe@...ches.com>
To:     Nathan Chancellor <natechancellor@...il.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 Sat, 2019-08-10 at 20:17 -0700, 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?

Coccinelle doesn't support transforming comments
so I am using a perl script for those transforms
that I will post when I'm happy enough with it.