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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 20 Apr 2018 16:38:29 +0200
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Subject: Re: [PATCH] x86: ipc: fix x32 version of shmid64_ds and msqid64_ds
To:     Jeffrey Walton <noloader@gmail.com>
Cc:     "the arch/x86 maintainers" <x86@kernel.org>,
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On Fri, Apr 20, 2018 at 3:53 PM, Jeffrey Walton <noloader@gmail.com> wrote:
>> +#if !defined(__x86_64__) || !defined(__ilp32__)
>>  #include <asm-generic/msgbuf.h>
>> +#else
>
> I understand there's some progress having Clang compile the kernel.
> Clang treats __ILP32__ and friends differently than GCC. I believe
> ILP32 shows up just about everywhere there are 32-bit ints, longs and
> pointers. You might find it on Aarch64 or you might find it on MIPS64
> when using Clang.
>
> I think that means this may be a little suspicious:
>
>     > +#if !defined(__x86_64__) || !defined(__ilp32__)
>
> I kind of felt LLVM was wandering away from the x32 ABI, but the LLVM
> devs insisted they were within their purview. Also see
> https://lists.llvm.org/pipermail/cfe-dev/2015-December/046300.html.
>
> Sorry about the top-post. I just wanted to pick out that one piece.

It seems I made a typo and it needs to be __ILP32__ rather than
__ilp32__ (corrected that locally, will resend once we have resolved
this).

Aside from that, the #if check seems to be correct to me: this
is an x86-specific header, so it won't ever be seen on other
architectures. On x86-32, __x86_64__ isn't set, so we don't care
about whether __ilp32__ is set or not, and on x86-64 (lp64),
__ilp32__ is never set, so we still get the asm-generic header.

      Arnd