From patchwork Tue Sep 14 09:02:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Jelinek X-Patchwork-Id: 44984 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 617933858413 for ; Tue, 14 Sep 2021 09:02:43 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 617933858413 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1631610163; bh=r97S0p6mq6VKdvL4zQxDBjBiNIFfmm7RaGaaPUnWvjI=; h=Date:To:Subject:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=EckR7X2jH42CIUV6k/1+SNnn9Ct7uTIGdxe0DRVmEqK6yzLK1y7P/duCQn54qX4QB D5zVbKI+yMuwxdHfKZPtnufcuuQqQ6dPNF67HwBzRara07nEdScjypsISh1JCR+1UG /tpcrjokQyBxgyo9KdGv8e2OnOLWyJDyOUYwzULU= 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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id E61DD3858402 for ; Tue, 14 Sep 2021 09:02:13 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E61DD3858402 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-542-s4lasVmbMNKsTc_cONUP3w-1; Tue, 14 Sep 2021 05:02:12 -0400 X-MC-Unique: s4lasVmbMNKsTc_cONUP3w-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8DD3F10168C3 for ; Tue, 14 Sep 2021 09:02:11 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.10]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2ABB35D9D3; Tue, 14 Sep 2021 09:02:11 +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 18E929Ok1720999 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 14 Sep 2021 11:02:09 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 18E927Ib1720998; Tue, 14 Sep 2021 11:02:07 +0200 Date: Tue, 14 Sep 2021 11:02:06 +0200 To: Jason Merrill Subject: [PATCH] c++: Update DECL_*SIZE for objects with flexible array members with initializers [PR102295] Message-ID: <20210914090206.GV304296@tucnak> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-5.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP 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 Cc: gcc-patches@gcc.gnu.org Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" Hi! The C FE updates DECL_*SIZE for vars which have initializers for flexible array members for many years, but C++ FE kept DECL_*SIZE the same as the type size (i.e. as if there were zero elements in the flexible array member). This results e.g. in ELF symbol sizes being too small. The following patch fixes that, bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? Note, if the flexible array member is initialized only with non-constant initializers, we have a worse bug that this patch doesn't solve, the splitting of initializers into constant and dynamic initialization removes the initializer and we don't have just wrong DECL_*SIZE, but nothing is emitted when emitting those vars into assembly either and so the dynamic initialization clobbers other vars that may overlap the variable. I think we need keep an empty CONSTRUCTOR elt in DECL_INITIAL for the flexible array member in that case. 2021-09-14 Jakub Jelinek PR c++/102295 * decl.c (layout_var_decl): For aggregates ending with a flexible array member, add the size of the initializer for that member to DECL_SIZE and DECL_SIZE_UNIT. * g++.target/i386/pr102295.C: New test. Jakub --- gcc/cp/decl.c.jj 2021-09-09 10:40:26.063176136 +0200 +++ gcc/cp/decl.c 2021-09-13 18:23:01.131587057 +0200 @@ -6091,6 +6091,38 @@ layout_var_decl (tree decl) error_at (DECL_SOURCE_LOCATION (decl), "storage size of %qD isn%'t constant", decl); TREE_TYPE (decl) = error_mark_node; + type = error_mark_node; + } + } + + /* If the final element initializes a flexible array field, add the size of + that initializer to DECL's size. */ + if (type != error_mark_node + && DECL_INITIAL (decl) + && TREE_CODE (DECL_INITIAL (decl)) == CONSTRUCTOR + && !vec_safe_is_empty (CONSTRUCTOR_ELTS (DECL_INITIAL (decl))) + && DECL_SIZE (decl) != NULL_TREE + && TREE_CODE (DECL_SIZE (decl)) == INTEGER_CST + && TYPE_SIZE (type) != NULL_TREE + && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST + && tree_int_cst_equal (DECL_SIZE (decl), TYPE_SIZE (type))) + { + constructor_elt &elt = CONSTRUCTOR_ELTS (DECL_INITIAL (decl))->last (); + if (elt.index) + { + tree itype = TREE_TYPE (elt.index); + tree vtype = TREE_TYPE (elt.value); + if (TREE_CODE (itype) == ARRAY_TYPE + && TYPE_DOMAIN (itype) == NULL + && TREE_CODE (vtype) == ARRAY_TYPE + && COMPLETE_TYPE_P (vtype)) + { + DECL_SIZE (decl) + = size_binop (PLUS_EXPR, DECL_SIZE (decl), TYPE_SIZE (vtype)); + DECL_SIZE_UNIT (decl) + = size_binop (PLUS_EXPR, DECL_SIZE_UNIT (decl), + TYPE_SIZE_UNIT (vtype)); + } } } } --- gcc/testsuite/g++.target/i386/pr102295.C.jj 2021-09-13 18:28:08.406370163 +0200 +++ gcc/testsuite/g++.target/i386/pr102295.C 2021-09-13 18:28:26.846117106 +0200 @@ -0,0 +1,12 @@ +// PR c++/102295 +// { dg-do compile { target *-*-linux* } } +// { dg-options "-Wno-pedantic" } + +struct S { + int a; + int b[]; +} S; + +struct S s = { 1, { 2, 3 } }; + +/* { dg-final { scan-assembler ".size\[\t \]*s, 12" } } */