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[Xen-devel] Re: [PATCH] Re: [Xen-staging] [xen-unstable] Explicitly tag

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] Re: [Xen-staging] [xen-unstable] Explicitly tag every anonymous aggregate in the public headers.
From: Alex Williamson <alex.williamson@xxxxxx>
Date: Mon, 31 Mar 2008 10:28:59 -0600
Cc: xen-ia64-devel <xen-ia64-devel@xxxxxxxxxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx>
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On Mon, 2008-03-31 at 17:21 +0100, Keir Fraser wrote:
> On 31/3/08 16:49, "Alex Williamson" <alex.williamson@xxxxxx> wrote:
> 
> > It seems pretty clear that in nesting __extension__ attributes in this
> > manner, the struct is actually ignored and the compiler is treating the
> > everything that was in the struct as a separate member of the union.  In
> > the mapped_regs example, the structure size remains correct only because
> > the union is full padded out using the full size arrays.  Please apply
> > the patch I sent previously to revert the nested __extension__
> > attributes.  Thanks,
> 
> __extension__ seems worryingly half-baked. We're better off asserting
> !__STRICT_ANSI__ in my opinion. I don't suppose you much care either way as
> long as ia64 boot works again. :-)

   Yup ;^)  FWIW, I still haven't been able to create a simple test
program that shows this behavior.  For these tests I've had to resort to
putting printks in xen.  There must be some build option we use that
tickles this issue.  Still, not good for an option that claims to have
no side effects.  Thanks,

        Alex

-- 
Alex Williamson                             HP Open Source & Linux Org.


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