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 1BCED382FCB9 for ; Wed, 14 Dec 2022 12:04:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1BCED382FCB9 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=1671019442; h=from:from: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=oT57y4PaMii+lYkle7tAgvrbVr0zkO00rXK/NL+Htis=; b=etvf4T0MhNB16/QxSuWCwMmf8SrbzKHmH/9J+0j8aFS8iIdsAnvHGWsDoTXH3Ln7VbW668 pG6z8DV7LRdW3P6LF3KHKZDw2Vzz5wYei4opxPPsmjFH0GJzw3ELVjovdFeQwqrF9U/uUJ 6fEj78s54qX0foJjaCeG3l/bRpW1A4A= 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-107-7_gSOdFZMaGJgwvHOIiFWQ-1; Wed, 14 Dec 2022 07:04:01 -0500 X-MC-Unique: 7_gSOdFZMaGJgwvHOIiFWQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 37C132A5956A; Wed, 14 Dec 2022 12:04:01 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.27]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 52FEC40C2064; Wed, 14 Dec 2022 12:04:00 +0000 (UTC) From: Florian Weimer To: Carlos O'Donell via Libc-alpha Cc: Noah Goldstein , Narayanan Iyer , Carlos O'Donell Subject: Re: Bug 29863 - Segmentation fault vs invalid results, memory models, and control/data dependencies. References: <0a1f01d90f1f$96c7ce60$c4576b20$@yottadb.com> <0b2901d90f26$f82b4720$e881d560$@yottadb.com> <422f9ec4-c72d-0396-9519-c72e85e5afc2@redhat.com> Date: Wed, 14 Dec 2022 13:03:56 +0100 In-Reply-To: <422f9ec4-c72d-0396-9519-c72e85e5afc2@redhat.com> (Carlos O'Donell via Libc-alpha's message of "Tue, 13 Dec 2022 17:52:26 -0500") Message-ID: <87sfhimbtf.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-5.0 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: * Carlos O'Donell via Libc-alpha: > - We should pursue performance given a well formed understanding of the memory > models glibc supports e.g. ISO C11, and POSIX Issue 7. But the C memory model is known to be broken. For example, it does not rule out the existence of out-of-thin-air values, which makes relaxed MO pretty useless. I don't think we can use it as an argument to reject requests from application developers. > - Authors using OCC should explain their memory model in detail, and > may need to raise the issue with the broader toolchain authors to gain > consensus for the design constraints imposed by OCC on the > implementation language being compiled e.g. compiler picks a special > memcpy, or does other operations. I think their requirements for memcmp are pretty clear. We don't need a fullly fleshed out memory model for that. Thanks, Florian