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Date: Wed, 28 Sep 2016 12:00:25 +0100
From: "Daniel P. Berrange" <berrange@redhat.com>
Message-ID: <20160928110025.GL21583@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] io: Fix double shift usages on QIOChannel
 features
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To: Felipe Franciosi <felipe@nutanix.com>
Cc: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau <mlureau@redhat.com>, Marc-Andre Lureau <marcandre.lureau@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On Wed, Sep 28, 2016 at 10:55:33AM +0000, Felipe Franciosi wrote:
> Hi Marc,
>=20
> > On 27 Sep 2016, at 18:12, Marc-Andr=C3=A9 Lureau <mlureau@redhat.com>=
 wrote:
> >=20
> > Hi
> >=20
> > ----- Original Message -----
> >> When QIOChannels were introduced in 666a3af9, the feature bits were
> >> defined shifted. However, when using them, the code was shifting the=
m
> >> again. The incorrect use was consistent until 74b6ce43, where
> >> QIO_CHANNEL_FEATURE_LISTEN was defined shifted but tested unshifted.
> >>=20
> >=20
> > And by luck, QIO_CHANNEL_FEATURE_LISTEN =3D=3D (1 << QIO_CHANNEL_FEAT=
URE_LISTEN), so it works :)
>=20
> Can you elaborate on that? Maybe I'm missing something obvious, but
> I'm confused as to how they are equivalent.

They're not equivalent  QIO_CHANNEL_FEATURE_LISTEN is (1 << 2) which
evaulates to 4 and 4 !=3D (1 << 4).


Regards,
Daniel
--=20
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