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    SubjectRe: [PATCH] Makefile: Convert -Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang
    On Mon, Aug 12, 2019 at 6:29 PM Nick Desaulniers
    <ndesaulniers@google.com> wrote:
    >
    > On Sat, Aug 10, 2019 at 8:06 PM Joe Perches <joe@perches.com> 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]]
    >
    > Isn't [[fallthrough]] the C++ style attribute? **eek** Seems to be a

    It is going to be very likely also the C spelling too, i.e. C2x will
    likely be released with attributes. [[fallthrough]] in particular is
    still on discussion but it may be included too (thanks Aaron!).

    > waste for Clang to implement __attribute__((fallthrough)) just as we
    > switch the kernel to not use it. Also, I'd recommend making the
    > preprocessor define all caps to help folks recognize it's a
    > preprocessor define.

    Hm... I would go for either __fallthrough as the rest of attributes,
    or simply fallthrough -- FALLTHROUGH seems wrong. If you want it that
    way for visibility, then I would choose __fallthrough, since the
    underscores are quite prominent and anyway IDEs typically highlight
    macros in a different color than keywords (return etc.).

    Cheers,
    Miguel

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