From patchwork Mon Jan 22 13:48:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Federico Serafini X-Patchwork-Id: 13525500 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 25FCBC47DDF for ; Mon, 22 Jan 2024 13:48:35 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.669905.1042419 (Exim 4.92) (envelope-from ) id 1rRuf2-0007dy-2U; Mon, 22 Jan 2024 13:48:24 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 669905.1042419; Mon, 22 Jan 2024 13:48:24 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rRuf1-0007dm-SH; Mon, 22 Jan 2024 13:48:23 +0000 Received: by outflank-mailman (input) for mailman id 669905; Mon, 22 Jan 2024 13:48:23 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rRuf0-0007Ly-VY for xen-devel@lists.xenproject.org; Mon, 22 Jan 2024 13:48:22 +0000 Received: from support.bugseng.com (mail.bugseng.com [162.55.131.47]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id e7c82d78-b92c-11ee-98f2-6d05b1d4d9a1; Mon, 22 Jan 2024 14:48:21 +0100 (CET) Received: from Dell.homenet.telecomitalia.it (host-87-16-84-78.retail.telecomitalia.it [87.16.84.78]) by support.bugseng.com (Postfix) with ESMTPSA id DE0684EE073C; Mon, 22 Jan 2024 14:48:20 +0100 (CET) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: e7c82d78-b92c-11ee-98f2-6d05b1d4d9a1 From: Federico Serafini To: xen-devel@lists.xenproject.org Cc: consulting@bugseng.com, Federico Serafini , Andrew Cooper , George Dunlap , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu Subject: [XEN PATCH 1/3] xen: introduce static_assert_unreachable() Date: Mon, 22 Jan 2024 14:48:06 +0100 Message-Id: <01c57c7e5131d699cf622be96fea7cd8e03c23f9.1705930767.git.federico.serafini@bugseng.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: MIME-Version: 1.0 Introduce macro static_asser_unreachable() to check that a program point is considered unreachable by the static analysis performed by the compiler, even at optimization level -O0. The use of such macro will lead to one of the following outcomes: - the program point identified by the macro is considered unreachable, then the compiler removes the macro; - the program point identified by the macro is not considered unreachable, then the compiler does not remove the macro, which will lead to a failure in the build process caused by an assembler error. Signed-off-by: Federico Serafini --- xen/include/xen/compiler.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h index 16d554f2a5..ad0520f5d4 100644 --- a/xen/include/xen/compiler.h +++ b/xen/include/xen/compiler.h @@ -64,6 +64,14 @@ # define fallthrough do {} while (0) /* fallthrough */ #endif +/* + * Add the following macro to check that a program point is considered + * unreachable by the static analysis performed by the compiler, + * even at optimization level -O0. + */ +#define static_assert_unreachable() \ + asm(".error \"unreachable program point reached\""); + #ifdef __clang__ /* Clang can replace some vars with new automatic ones that go in .data; * mark all explicit-segment vars 'used' to prevent that. */