From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37303) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d2wyu-0002yC-5O for qemu-devel@nongnu.org; Tue, 25 Apr 2017 05:42:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d2wyr-0001Uw-1d for qemu-devel@nongnu.org; Tue, 25 Apr 2017 05:42:00 -0400 Sender: Richard Henderson References: <20170425083555.13547-1-nikunj@linux.vnet.ibm.com> From: Richard Henderson Message-ID: <052c8b5a-5056-5867-c4c8-11a8735d69a5@twiddle.net> Date: Tue, 25 Apr 2017 11:41:52 +0200 MIME-Version: 1.0 In-Reply-To: <20170425083555.13547-1-nikunj@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH RFC] configure: fix clang failure for libatomic List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nikunj A Dadhania , qemu-ppc@nongnu.org, qemu-devel@nongnu.org, david@gibson.dropbear.id.au Cc: alex.bennee@linaro.org, peter.maydell@linaro.org, pbonzini@redhat.com On 04/25/2017 10:35 AM, Nikunj A Dadhania wrote: > if compile_prog "" "" ; then > atomic128=yes > + elif compile_prog "" "-latomic" ; then > + atomic128=yes > + lib_atomic="-latomic" > fi This is a problem, because I think you'll find that gcc now advertises CONFIG_ATOMIC128 for *all* hosts. This is because by definition, libatomic supplies fallback routines for types of arbitrary size. However, the fallback routines use locking, not actual atomic operations. So the configure test is no longer testing what we intended. r~