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Date: Tue, 9 Aug 2016 09:13:31 +0100
From: "Daniel P. Berrange" <berrange@redhat.com>
Message-ID: <20160809081331.GC1530@redhat.com>
Reply-To: "Daniel P. Berrange" <berrange@redhat.com>
References: <20160809023545.30204-1-bobby.prani@gmail.com>
	<CAFEAcA8U30vhKw4VQFSuMk9eKUJhL26Mb14pZiekKyaxuddZTg@mail.gmail.com>
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Subject: Re: [Qemu-devel] [PATCH] clang: Disable warning about expansion to
 'defined'
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Pranith Kumar <bobby.prani@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau <marcandre.lureau@redhat.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, "open list:All patches CC here" <qemu-devel@nongnu.org>

On Tue, Aug 09, 2016 at 09:09:13AM +0100, Peter Maydell wrote:
> On 9 August 2016 at 03:35, Pranith Kumar <bobby.prani@gmail.com> wrote:
> > Clang produces the following warning. The warning is detailed here:
> > https://reviews.llvm.org/D15866. Disable the warning.
> >
> > /home/pranith/devops/code/qemu/hw/display/qxl.c:507:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
> > #if SPICE_NEEDS_SET_MM_TIME
> >     ^
> > /home/pranith/devops/code/qemu/include/ui/qemu-spice.h:46:5: note: expanded from macro 'SPICE_NEEDS_SET_MM_TIME'
> >   (!defined(SPICE_SERVER_VERSION) || (SPICE_SERVER_VERSION < 0xc06))
> >     ^
> > /home/pranith/devops/code/qemu/hw/display/qxl.c:1074:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
> > #if SPICE_NEEDS_SET_MM_TIME
> >     ^
> > /home/pranith/devops/code/qemu/include/ui/qemu-spice.h:46:5: note: expanded from macro 'SPICE_NEEDS_SET_MM_TIME'
> >   (!defined(SPICE_SERVER_VERSION) || (SPICE_SERVER_VERSION < 0xc06))
> 
> Is this the only thing in our code which provokes the warning?
> If so, why don't we just fix it to not be undefined behaviour?

Indeed, it looks like it could be fixed by changing include/ui/qemu-spice.h


#define SPICE_NEEDS_SET_MM_TIME                                       \
  (!defined(SPICE_SERVER_VERSION) || (SPICE_SERVER_VERSION < 0xc06))


to be

#if !defined(SPICE_SERVER_VERSION) || (SPICE_SERVER_VERSION < 0xc06)
#define SPICE_NEEDS_SET_MM_TIME
#endif


Regards,
Daniel
-- 
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