From patchwork Thu May 10 17:45:05 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Peter Maydell X-Patchwork-Id: 10392119 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 67FFE60236 for ; Thu, 10 May 2018 17:47:05 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5942028C86 for ; Thu, 10 May 2018 17:47:05 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4E4F328C8B; Thu, 10 May 2018 17:47:05 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 0020928C86 for ; Thu, 10 May 2018 17:47:04 +0000 (UTC) Received: from localhost ([::1]:34976 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fGpei-0006DU-7h for patchwork-qemu-devel@patchwork.kernel.org; Thu, 10 May 2018 13:47:04 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48438) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fGpd9-0004zV-Sg for qemu-devel@nongnu.org; Thu, 10 May 2018 13:45:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fGpd9-0000qW-0y for qemu-devel@nongnu.org; Thu, 10 May 2018 13:45:27 -0400 Received: from orth.archaic.org.uk ([2001:8b0:1d0::2]:41596) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fGpd8-0000nR-Oi for qemu-devel@nongnu.org; Thu, 10 May 2018 13:45:26 -0400 Received: from pm215 by orth.archaic.org.uk with local (Exim 4.89) (envelope-from ) id 1fGpd7-0003Vu-Gh for qemu-devel@nongnu.org; Thu, 10 May 2018 18:45:25 +0100 From: Peter Maydell To: qemu-devel@nongnu.org Date: Thu, 10 May 2018 18:45:05 +0100 Message-Id: <20180510174519.11264-8-peter.maydell@linaro.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180510174519.11264-1-peter.maydell@linaro.org> References: <20180510174519.11264-1-peter.maydell@linaro.org> MIME-Version: 1.0 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2001:8b0:1d0::2 Subject: [Qemu-devel] [PULL 07/21] atomic.h: Work around gcc spurious "unused value" warning X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Some versions of gcc produce a spurious warning if the result of __atomic_compare_echange_n() is not used and the type involved is a signed 8 bit value: error: value computed is not used [-Werror=unused-value] This has been seen on at least gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609 Work around this by using an explicit cast to void to indicate that we don't care about the return value. We don't currently use our atomic_cmpxchg() macro on any signed 8 bit types, but the upcoming support for the Arm v8.1-Atomics will require it. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daudé --- include/qemu/atomic.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index d73c9e14d7..9ed39effd3 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -187,7 +187,7 @@ /* Returns the eventual value, failed or not */ #define atomic_cmpxchg__nocheck(ptr, old, new) ({ \ typeof_strip_qual(*ptr) _old = (old); \ - __atomic_compare_exchange_n(ptr, &_old, new, false, \ + (void)__atomic_compare_exchange_n(ptr, &_old, new, false, \ __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \ _old; \ })