From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:45806)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <peter.maydell@linaro.org>) id 1ZvkHJ-0006gQ-Vo
	for qemu-devel@nongnu.org; Mon, 09 Nov 2015 06:06:26 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <peter.maydell@linaro.org>) id 1ZvkHJ-0003ge-1U
	for qemu-devel@nongnu.org; Mon, 09 Nov 2015 06:06:25 -0500
Received: from mail-yk0-x235.google.com ([2607:f8b0:4002:c07::235]:35337)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <peter.maydell@linaro.org>) id 1ZvkHI-0003gY-TT
	for qemu-devel@nongnu.org; Mon, 09 Nov 2015 06:06:24 -0500
Received: by ykek133 with SMTP id k133so258090946yke.2
	for <qemu-devel@nongnu.org>; Mon, 09 Nov 2015 03:06:24 -0800 (PST)
MIME-Version: 1.0
In-Reply-To: <564073AE.6010602@redhat.com>
References: <ABB58126-7C59-400D-88A8-1BEB7D1F7078@yahoo.com>
	<CAFEAcA_D87kcL8hF651BymjPMep3qqwUQiOhi7RjWb0t67bGiw@mail.gmail.com>
	<CAFEAcA__CS+zvJacotcioK0p3q4p2rA90jz-uLj+1LkUnv3rOA@mail.gmail.com>
	<CAFEAcA-z=qVNi7f-REAcTtA5nF5Ps78us7mVOnucCTi1=7K-Lg@mail.gmail.com>
	<56406315.6050402@redhat.com>
	<CAFEAcA-FXzNyoQgbKn+gbCACBQOwPsTtQxBrEqc=-TrRJNY2pw@mail.gmail.com>
	<564073AE.6010602@redhat.com>
From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 9 Nov 2015 11:06:05 +0000
Message-ID: <CAFEAcA9oery-wy5rjFqEaQ1DWrYWR9zMRzWb3HPWAcbmMCDi3w@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [Qemu-devel] Qemu: Guest Linux hangs on Mac OS X 10.11
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: Paolo Bonzini <pbonzini@redhat.com>
Cc: Aaron Elkins <threcius@yahoo.com>, "qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>

On 9 November 2015 at 10:21, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Hmm, so the list is pretty short:

The good news is that my second bisect conclusively fingered
the culprit for why the bug went away...

>       configure: disable FORTIFY_SOURCE under clang

...the bad news is it's because this patch inadvertently makes
all non-fortify-source compiles be no-optimization (and we already
knew the bug didn't repro in an unoptimized build).

This also explains the weird behaviour in bisect: it was only
when some later commit touched enough of the header files to
force recompilation of whichever object file it is that's
being problematic that the bug disappeared.

thanks
-- PMM