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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 33DDDC433E0 for ; Tue, 23 Feb 2021 16:17:08 +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 C3B3F600CC for ; Tue, 23 Feb 2021 16:17:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C3B3F600CC 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]:59532 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lEaN0-0002yS-VV for qemu-devel@archiver.kernel.org; Tue, 23 Feb 2021 11:17:07 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34952) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lEaIW-0006r9-PW for qemu-devel@nongnu.org; Tue, 23 Feb 2021 11:12:28 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44463) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lEaIT-0007dD-BU for qemu-devel@nongnu.org; Tue, 23 Feb 2021 11:12:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614096744; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JhwiwkreM19H55eQuA8oFcGhbBa9TZVlAiZpy+p1j2k=; b=bWxH+vDM/CiR+ZFcKqQxf7vMLc2CmdhGp4zTVXgM60Kz8ydousloZnT3jLYg7OZhuC2qVJ F6NZZMYu0Xd8GvZoDR8NKAfIIB2VpXHS/4iJA8BCgUqSBAMwjhZqWgRfLBnPgWEmX/RWzY wAMD6gmClV6zuYPgc2VTwTKLclbtLbM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-441-U-JMOFb6Nki9AKUzKoM_yA-1; Tue, 23 Feb 2021 11:12:09 -0500 X-MC-Unique: U-JMOFb6Nki9AKUzKoM_yA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 015C0189F1AD; Tue, 23 Feb 2021 16:08:04 +0000 (UTC) Received: from redhat.com (ovpn-115-33.ams2.redhat.com [10.36.115.33]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0115D5C675; Tue, 23 Feb 2021 16:08:02 +0000 (UTC) Date: Tue, 23 Feb 2021 16:07:59 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Maydell Subject: Re: [PATCH] disas: Fix build with glib2.0 >=2.67.3 Message-ID: References: <20210223145646.4129643-1-christian.ehrhardt@canonical.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.5 (2021-01-21) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: qemu-devel , Christian Ehrhardt Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Feb 23, 2021 at 03:43:48PM +0000, Peter Maydell wrote: > On Tue, 23 Feb 2021 at 15:03, Christian Ehrhardt > wrote: > > > > glib2.0 introduced a change in 2.67.3 and later which triggers an > > issue [1] for anyone including it's headers in a "extern C" context > > which a few files in disas/* do. An example of such an include chain > > and error look like: > > > > ../../disas/arm-a64.cc > > In file included from /usr/include/glib-2.0/glib/gmacros.h:241, > > from /usr/lib/x86_64-linux-gnu/glib-2.0/include/glibconfig.h:9, > > from /usr/include/glib-2.0/glib/gtypes.h:32, > > from /usr/include/glib-2.0/glib/galloca.h:32, > > from /usr/include/glib-2.0/glib.h:30, > > from /<>/qemu-5.2+dfsg/include/glib-compat.h:32, > > from /<>/qemu-5.2+dfsg/include/qemu/osdep.h:126, > > from ../../disas/arm-a64.cc:21: > > /usr/include/c++/10/type_traits:56:3: error: template with C linkage > > 56 | template > > | ^~~~~~~~ > > ../../disas/arm-a64.cc:20:1: note: ‘extern "C"’ linkage started here > > 20 | extern "C" { > > | ^~~~~~~~~~ > > > > To fix that move the include of osdep.h out of that section. It was added > > already as C++ fixup by e78490c44: "disas/arm-a64.cc: Include osdep.h first". > > > > [1]: https://gitlab.gnome.org/GNOME/glib/-/issues/2331 > > I'm not convinced by this as a fix, though I'm happy to be corrected > by somebody with a fuller understanding of C++. glib.h may be supposed > to work as a C++ header, but osdep.h as a whole is definitely a C header, > so I think it ought to be inside 'extern C'; and it has to be > the first header included; and it happens to want to include glib.h. > > Fixing glib.h seems like it would be nicer, assuming they haven't > already shipped this breakage. Failing that, does it work to do: This was raised in Fedora and upstream GLib already https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1935 https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/thread/J3P4TRHLWNDIKXF76OLYZNAPTABCZ3U5/#7LXFUDBBBIT23FE44QJYWX3I7U4EHW6M The key comment there is this one: "Note that wrapping the header include in an extern declaration violates C++ standard requirements. ("A translation unit shall include a header only outside of any declaration or definition", [using.headers]/3)" IOW, if we need to make osdep.h safe to use from C++, then we need to put the 'extern "C" { ... }' bit in osdep.h itself, not in the things which include it. > > /* > * glib.h expects to be included as a C++ header if we're > * building a C++ file, but osdep.h and thus glib-compat.h are > * C headers and should be inside an "extern C" block. > */ > #ifdef __cplusplus > extern "C++" { > #include > #if defined(G_OS_UNIX) > #include > #endif > } > > in include/glib-compat.h ? That'd be even worse. We need to make headers that need to be used from C++ code follow the pattern: #include #include #include ...all other includs.. extern "C" { .. only the declarations, no #includes ... }; Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|