From patchwork Wed Mar 30 10:07:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Jelinek X-Patchwork-Id: 1611013 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=gcc.gnu.org header.i=@gcc.gnu.org header.a=rsa-sha256 header.s=default header.b=eCW7on0Q; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org (client-ip=2620:52:3:1:0:246e:9693:128c; helo=sourceware.org; envelope-from=gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org; receiver=) Received: from sourceware.org (server2.sourceware.org [IPv6:2620:52:3:1:0:246e:9693:128c]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4KT2Fp5K6vz9sFq for ; Wed, 30 Mar 2022 21:08:46 +1100 (AEDT) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 84944385840C for ; Wed, 30 Mar 2022 10:08:44 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 84944385840C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1648634924; bh=c8AHrG5+NtLMfUo2BbM7+wwfdN45CUr3IRfhJNc+9CM=; h=Date:To:Subject:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=eCW7on0Q7Bv5x4qvHmJFLb91+fTMP45rVFD6CBds+xly5SQUkTPbsK8iFAPPzxvwl +Dm2Y7XFylwi6Armvjd99t4mDvLO+zWDVb2Hw1P5FTj+H9Ood2X5Kx0V9lI0WioF79 AGNg9h1yXjke6R1MQZKPxdUBBhb7q9Q45b/z3EOA= X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 80C8F385840C for ; Wed, 30 Mar 2022 10:08:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 80C8F385840C Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-455-1CcDa8TWOVmE9M4pbEWNXA-1; Wed, 30 Mar 2022 06:07:59 -0400 X-MC-Unique: 1CcDa8TWOVmE9M4pbEWNXA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9C8273C021AD; Wed, 30 Mar 2022 10:07:58 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.15]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 54B43C07F48; Wed, 30 Mar 2022 10:07:58 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.16.1/8.16.1) with ESMTPS id 22UA7tLF158511 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 30 Mar 2022 12:07:56 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 22UA7tKW158510; Wed, 30 Mar 2022 12:07:55 +0200 Date: Wed, 30 Mar 2022 12:07:55 +0200 To: gcc-patches@gcc.gnu.org Subject: [wwwdocs] Document zero width bit-field passing ABI changes in gcc-12/changes.html [PR104796] Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.85 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-10.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Jakub Jelinek via Gcc-patches From: Jakub Jelinek Reply-To: Jakub Jelinek Errors-To: gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org Sender: "Gcc-patches" Hi! This patch documents the PR102024 ABI changes. The x86-64, ARM and AArch64 backends refer to this in their -Wpsabi diagnostics. Ok for wwwdocs? Jakub diff --git a/htdocs/gcc-12/changes.html b/htdocs/gcc-12/changes.html index 689feeba..dc0e4074 100644 --- a/htdocs/gcc-12/changes.html +++ b/htdocs/gcc-12/changes.html @@ -28,6 +28,31 @@ a work-in-progress.

Caveats

    +
  • + An ABI incompatibility between C and + C++ when passing or returning by value certain aggregates with zero + width bit-fields has been discovered on various targets. + As mentioned in PR102024, + since the PR42217 fix in + GCC 4.5 the C++ front-end has been removing zero width bit-fields + from the internal representation of the aggregates after the layout of those + aggregates, but the C front-end kept them, so passing e.g. + struct S { float a; int : 0; float b; } or + struct T { float c; int : 0; } by value could differ + between C and C++. Starting with GCC 12 the C++ front-end no longer + removes those bit-fields from the internal representation and + per clarified psABI some targets have been changed, so that they + either ignore those bit-fields in the argument passing by value + decisions in both C and C++, or they always take them into account. + x86-64, ARM and AArch64 will always ignore them (so there is + a C ABI incompatibility between GCC 11 and earlier with GCC 12 or + later), PowerPC64 ELFv2 and S/390 always take them into account + (so there is a C++ ABI incompatibility, GCC 4.4 and earlier compatible + with GCC 12 or later, incompatible with GCC 4.5 through GCC 11). + RISC-V has changed the handling of these already starting with GCC 10. + GCC 12 on the above targets will report such incompatibilities as + warnings or other diagnostics unless -Wno-psabi is used. +
  • C: Computed gotos require a pointer type now.