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 [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id C1D36385840F for ; Fri, 24 Feb 2023 14:08:54 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org C1D36385840F Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1677247734; 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:in-reply-to:in-reply-to: references:references; bh=iKp1a/t3JfG7JGG6rqfk9pBrrx2XtkGOf50vBCuZ7A0=; b=U8OId6vY/m6RI/euxFF/8soY9wil9jDMWMjF7b34BYJMlCHBb+jOPwswFszFa96Nw+UHB2 dazyxzQ/8dqFtQLAsjuH0YaDUDpFyR/Mn0edHHt8VJuoRGMB9mmUP0GhDbIdWlNo++p0Pf C3v5J3qqxf15+7S9F7x7AgsB/CVz5ws= 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-111-gc1VGr3MMu2IkS8CtSMNrQ-1; Fri, 24 Feb 2023 09:08:51 -0500 X-MC-Unique: gc1VGr3MMu2IkS8CtSMNrQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CFC1C1C05154; Fri, 24 Feb 2023 14:08:50 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.62]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 920A6492B12; Fri, 24 Feb 2023 14:08:50 +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 31OE8mNT871916 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 24 Feb 2023 15:08:48 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 31OE8l8n871915; Fri, 24 Feb 2023 15:08:47 +0100 Date: Fri, 24 Feb 2023 15:08:47 +0100 From: Jakub Jelinek To: Richard Biener Cc: gcc-patches@gcc.gnu.org Subject: Re: [PATCH 2/2] Avoid default-initializing auto_vec storage, fix vec Message-ID: Reply-To: Jakub Jelinek References: <20230224134739.D386F13246@imap2.suse-dmz.suse.de> MIME-Version: 1.0 In-Reply-To: <20230224134739.D386F13246@imap2.suse-dmz.suse.de> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 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=-3.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Fri, Feb 24, 2023 at 02:47:39PM +0100, Richard Biener wrote: > * vec.h (vec::m_vecdata): Remove. > (vec::m_vecpfx): Align as T to avoid > changing alignment of vec and simplifying > address. > (vec::address): Compute as this + 1. > (vec::embedded_size): Use sizeof the > vector instead of the offset of the m_vecdata member. > (auto_vec::m_data): Turn storage into > uninitialized unsigned char. > (auto_vec::auto_vec): Allow allocation of one > stack member. Initialize m_vec in a special way to > avoid later stringop overflow diagnostics. > * vec.cc (test_auto_alias): New. > (vec_cc_tests): Call it. > @@ -1559,8 +1560,14 @@ class auto_vec : public vec > public: > auto_vec () > { > - m_auto.embedded_init (MAX (N, 2), 0, 1); > - this->m_vec = &m_auto; > + m_auto.embedded_init (N, 0, 1); > + /* ??? Instead of initializing m_vec from &m_auto directly use an > + expression that avoids refering to a specific member of 'this' > + to derail the -Wstringop-overflow diagnostic code, avoiding > + the impression that data accesses are supposed to be to the > + m_auto memmber storage. */ s/memmber/member/ > + size_t off = (char *) &m_auto - (char *) this; > + this->m_vec = (vec *) ((char *) this + off); > } > > auto_vec (size_t s CXX_MEM_STAT_INFO) > @@ -1571,7 +1578,7 @@ public: > return; > } > > - m_auto.embedded_init (MAX (N, 2), 0, 1); > + m_auto.embedded_init (N, 0, 1); > this->m_vec = &m_auto; Don't we need the above 2 lines here as well (perhaps with a shorter comment just referencing the earlier comment)? Otherwise LGTM, thanks. Jakub