From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35390) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUAul-0007bk-A4 for qemu-devel@nongnu.org; Thu, 19 Jan 2017 06:30:00 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cUAuh-0007Tc-BX for qemu-devel@nongnu.org; Thu, 19 Jan 2017 06:29:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34510) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cUAuh-0007Sw-6d for qemu-devel@nongnu.org; Thu, 19 Jan 2017 06:29:55 -0500 Date: Thu, 19 Jan 2017 11:29:49 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20170119112949.GD2085@work-vm> References: <1484771412-28024-1-git-send-email-mst@redhat.com> <1484771412-28024-4-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1484771412-28024-4-git-send-email-mst@redhat.com> Subject: Re: [Qemu-devel] [PATCH 3/4] compiler: expression version of QEMU_BUILD_BUG_ON List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, Richard Henderson , Peter Maydell * Michael S. Tsirkin (mst@redhat.com) wrote: > QEMU_BUILD_BUG_ON uses a typedef in order to be safe > to use outside functions, but sometimes it's useful > to have a version that can be used within an expression. > Following what Linux does, introduce QEMU_BUILD_BUG_ON_ZERO > that return zero after checking condition at build time. > > Signed-off-by: Michael S. Tsirkin > --- > include/qemu/compiler.h | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h > index 1a9eeb9..d2b05dd 100644 > --- a/include/qemu/compiler.h > +++ b/include/qemu/compiler.h > @@ -88,6 +88,8 @@ > #define QEMU_BUILD_BUG_ON(x) \ > typedef char glue(qemu_build_bug_on__,__LINE__)[(x)?-1:1] __attribute__((unused)) > > +#define QEMU_BUILD_BUG_ON_ZERO(x) (sizeof(int[(x)?-1:1]) - sizeof(int)) > + Yes, pretty much the same as: https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg07090.html I'd used -sizeof(int[1]) in the right hand size to match the left, but I think it should always be the same. Reviewed-by: Dr. David Alan Gilbert > #if defined __GNUC__ > # if !QEMU_GNUC_PREREQ(4, 4) > /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */ > -- > MST > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK