From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54862C7618B for ; Fri, 26 Jul 2019 09:32:44 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2A37022C7E for ; Fri, 26 Jul 2019 09:32:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2A37022C7E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37738 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqwah-0002lN-DA for qemu-devel@archiver.kernel.org; Fri, 26 Jul 2019 05:32:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38551) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hqwaS-0002NK-Qs for qemu-devel@nongnu.org; Fri, 26 Jul 2019 05:32:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hqwaM-0000Qy-Em for qemu-devel@nongnu.org; Fri, 26 Jul 2019 05:32:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37634) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hqwaJ-0008FP-73; Fri, 26 Jul 2019 05:32:19 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9497B3071D7E; Fri, 26 Jul 2019 09:32:12 +0000 (UTC) Received: from work-vm (ovpn-117-185.ams2.redhat.com [10.36.117.185]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E78CD5D719; Fri, 26 Jul 2019 09:32:10 +0000 (UTC) Date: Fri, 26 Jul 2019 10:32:08 +0100 From: "Dr. David Alan Gilbert" To: Peter Maydell Message-ID: <20190726093208.GC2657@work-vm> References: <20190725163710.11703-1-peter.maydell@linaro.org> <20190725163710.11703-3-peter.maydell@linaro.org> <20190725172712.GM2656@work-vm> <20190725180007.GN2656@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.0 (2019-05-25) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Fri, 26 Jul 2019 09:32:12 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH for-4.1? 2/2] vmstate.h: Type check VMSTATE_STRUCT_VARRAY macros X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Damien Hedde , qemu-arm , QEMU Developers , Juan Quintela Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Maydell (peter.maydell@linaro.org) wrote: > On Thu, 25 Jul 2019 at 19:00, Dr. David Alan Gilbert > wrote: > > > > * Peter Maydell (peter.maydell@linaro.org) wrote: > > > On Thu, 25 Jul 2019 at 18:27, Dr. David Alan Gilbert > > > wrote: > > > > > > > > * Peter Maydell (peter.maydell@linaro.org) wrote: > > > > > #define type_check_2darray(t1,t2,n,m) ((t1(*)[n][m])0 - (t2*)0) > > > > > +/* Check that t2 is an array of t1 of size n */ > > > > > #define type_check_array(t1,t2,n) ((t1(*)[n])0 - (t2*)0) > > > > > > > > I'd have to admit I don't understand why that does what you say; > > > > I'd expected something to index a t2 pointer with [n]. > > > > > > Note that this is just a comment describing what the existing > > > macro does, as a way to distinguish its job from that of the > > > new macro I'm adding. > > > > > > What happens here is that t2 is a type like "foo [32]", ie > > > it is an array type already. t1 is the base 'foo' type; so the macro > > > is checking that t1[n] matches t2, where n is passed in to us > > > and must match the declared array size of the field (32 in > > > my example). (In C the size of the array is carried around as > > > part of its type, and must match on both sides of the expression; > > > so if you pass in the name of an array field that's the wrong size the > > > type check will fail, which is what we want.) > > > > Ah, OK that makes sense; what it really needs is that example to make > > me realise that t2 was already the array. > > Would > > /* > * Check that type t2 is an array of type t1 of size n, > * eg if t1 is 'foo' and n is 32 then t2 must be 'foo[32]' > */ > > be clearer ? Yep. Dave > thanks > -- PMM -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK