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From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 18 Jan 2016 20:49:23 +0000
Message-ID: <CAFEAcA_vQtww+mG6DMNfBBsSBjJ9854E2P9oxWWzLHTqfrAz2g@mail.gmail.com>
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Subject: Re: [Qemu-devel] CMSG_SPACE() causing compile time error on Mac OS X
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To: Programmingkid <programmingkidx@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel qemu-devel <qemu-devel@nongnu.org>

On 18 January 2016 at 19:50, Programmingkid <programmingkidx@gmail.com> wro=
te:
> I tried what Peter Maydell did and here are the results:
>
> typedef __darwin_size_t size_t;
>
> char control[(((__darwin_size_t)((char *)(__darwin_size_t)(sizeof(struct =
cmsghdr)) + (sizeof(__uint32_t) - 1)) &~ (sizeof(__uint32_t) - 1)) + ((__da=
rwin_size_t)((char *)(__darwin_size_t)(sizeof(int) * 16) + (sizeof(__uint32=
_t) - 1)) &~ (sizeof(__uint32_t) - 1)))] =3D { 0 };
>
> It looks like the problem was actually with this part: =3D { 0 };

No, the problem is that the compiler seems to think the bit in []
is not compile time constant (the =3D { 0 } initializer syntax
is valid if and only if it is compile-time-constant).

Can you say what 'gcc --version' prints for you? That will
tell us the clang version number, which is more interesting
than what clang claims its gcc-compatibility is.

I'm leaning towards this being a compiler bug fixed in
a later version of clang, because that [] expression looks
like it should be constant to me, and it's constant as
far as my clang version thinks.

thanks
-- PMM