From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:33496)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <olaf@aepfle.de>) id 1aOUxk-0005e9-PC
	for qemu-devel@nongnu.org; Wed, 27 Jan 2016 13:37:05 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <olaf@aepfle.de>) id 1aOUxh-0003s7-Jy
	for qemu-devel@nongnu.org; Wed, 27 Jan 2016 13:37:04 -0500
Received: from mo6-p00-ob.smtp.rzone.de ([2a01:238:20a:202:5300::12]:64790)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <olaf@aepfle.de>) id 1aOUxh-0003ra-AK
	for qemu-devel@nongnu.org; Wed, 27 Jan 2016 13:37:01 -0500
Date: Wed, 27 Jan 2016 19:23:52 +0100
From: Olaf Hering <olaf@aepfle.de>
Message-ID: <20160127182352.GA5526@aepfle.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
Subject: [Qemu-devel] qemu-upstream compile failure in
 intel_iommu.c:vtd_context_device_invalidate
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: xen-devel@lists.xensource.com, qemu-devel@nongnu.org

Compiling qemu-xen at 2ce1d30 ("xenfb.c: avoid expensive loops when prod
<= out_cons") leads to this error with -O1:

xen.git/tools/qemu-xen-dir/hw/i386/intel_iommu.c: In function ‘vtd_context_device_invalidate’:
xen.git/tools/qemu-xen-dir/hw/i386/intel_iommu.c:911:46: error: ‘mask’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
             if (vtd_as && ((devfn_it & mask) == (devfn & mask))) {
                                              ^
It works with -O2. From the code flow its clear that mask is always
initialized. Looks like gcc 5.2.1 does no proper diagnostic at -O1.
What should be done with such issues, are they fixed in the code?

Olaf