From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 66DC53851175 for ; Tue, 28 Jun 2022 18:49:40 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 66DC53851175 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-436-Fujj8_KLMbW4bBmdb1udVg-1; Tue, 28 Jun 2022 14:49:37 -0400 X-MC-Unique: Fujj8_KLMbW4bBmdb1udVg-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 A341A811E75; Tue, 28 Jun 2022 18:49:36 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.30]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 63297C28115; Tue, 28 Jun 2022 18:49:36 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.17.1/8.17.1) with ESMTPS id 25SInXxG3982365 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 28 Jun 2022 20:49:33 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 25SInWix3982364; Tue, 28 Jun 2022 20:49:32 +0200 Date: Tue, 28 Jun 2022 20:49:32 +0200 From: Jakub Jelinek To: Qing Zhao Cc: gcc-patches Paul A Clarke via , kees Cook , Martin Sebor Subject: Re: [GCC 13][PATCH] PR101836: Add a new option -fstrict-flex-array[=n] and use it in __builtin_object_size Message-ID: Reply-To: Jakub Jelinek References: <45936DE9-4099-4ED2-8B2B-6956A2FB493D@oracle.com> <5281C7CE-2677-4FE3-8ED3-C5B378685DCB@oracle.com> <2DDA999B-58B1-4390-9E2E-C4D68C0FD913@oracle.com> <865160D2-76C2-4B90-BD42-0CA676E6D3F0@oracle.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.85 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-3.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) 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-List-Received-Date: Tue, 28 Jun 2022 18:49:41 -0000 On Tue, Jun 28, 2022 at 06:29:01PM +0000, Qing Zhao wrote: > > > > On Jun 28, 2022, at 2:22 PM, Jakub Jelinek wrote: > > > > On Tue, Jun 28, 2022 at 06:15:58PM +0000, Qing Zhao wrote: > >>> Because the flag just tells whether some array shouldn't be treated as (poor man's) > >>> flexible array member. We still need to find out if some FIELD_DECL is to > >>> be treated like a flexible array member, which is a minority of > >>> COMPONENT_REFs. > >>> struct S { int a; char b[0]; int c; } s; > >>> struct T { int d; char e[]; }; > >>> struct U { int f; struct T g; int h; } u; > >>> Neither s.b nor u.g.e is to be treated like flexible array member, > >>> no matter what -fstrict-flex-array= option is used. > >> > >> Then, to resolve this issue, we might need a opposite flag DECL_IS_FLEXARRAY in FIELD_DECL? > >> > >> The default is FALSE for all FIELD_DECL. > > > > Doesn't matter whether it is positive or negative, you still need to analyze > > it. See the above example. If you have struct T t; and test t.e, then it > > is flexarray. But u.g.e is not, even when the COMPONENT_REF refers to the > > same FIELD_DECL. In the t.e case e is the very last field, in the latter > > case u.g.e is the last field in struct T, but struct U has the h field after > > So, do you mean that the current FE analysis will not be able to decide whether a specific array field is at the end of the enclosing structure? > Only the middle end can decide this ? Well, anything that analyzes it, can be in the FE or middle-end, but there is no place to store it for later. Jakub