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Re: [Xen-devel] xen build error on gcc v4.5.0

To: M A Young <m.a.young@xxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] xen build error on gcc v4.5.0
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 18 Aug 2010 20:55:28 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Masroor Vettuparambil <Masroor.Vettuparambil@xxxxxxxx>
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On 18/08/2010 20:44, "M A Young" <m.a.young@xxxxxxxxxxxx> wrote:

> On Wed, 18 Aug 2010, Jeremy Fitzhardinge wrote:
>> Looks like a gcc bug.  Older gccs can compute __RING_SIZE() as a
>> compile-time constant, but gcc 4.5.0 apparently isn't doing that.  It
>> is, admittedly, a very complex expression, but gcc shouldn't regress
>> like this.  I'm not sure how to work around it.
> One option is to use __CONST_RING_SIZE instead of __RING_SIZE if that is
> available. I had a similar problem compiling xen with gcc 4.5 where this
> worked.

Yes that is exactly why Jan Beulich introduced __CONST_RING_SIZE, in
xen-unstable:20975. Should be a simple patch to pv_ops netfront/back drivers
to make use of it.

 -- Keir

> Michael Young

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