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 [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id E1716385AC22 for ; Fri, 17 Sep 2021 14:27:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E1716385AC22 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-275-dewWw7YnNMCZMafItyIPGw-1; Fri, 17 Sep 2021 10:27:02 -0400 X-MC-Unique: dewWw7YnNMCZMafItyIPGw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 37C22100C63F; Fri, 17 Sep 2021 14:27:01 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E9C7B781ED; Fri, 17 Sep 2021 14:26:59 +0000 (UTC) From: Florian Weimer To: Joseph Myers Cc: Richard Biener , GCC Development , GNU C Library Subject: Re: [libc-coord] Add new ABI '__memcmpeq()' to libc References: Date: Fri, 17 Sep 2021 16:26:58 +0200 In-Reply-To: (Joseph Myers's message of "Fri, 17 Sep 2021 14:19:53 +0000") Message-ID: <87lf3vb7m5.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.7 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: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 17 Sep 2021 14:27:05 -0000 * Joseph Myers: > I was supposing a build-time decision (using GCC_GLIBC_VERSION_GTE_IFELSE > to know if the glibc version on the target definitely has this function). > But if we add a header declaration, you could check for __memcmpeq being > declared (and so cover arbitrary C libraries, not just glibc, and avoid > issues of needing to disable this logic for freestanding compilations, > which would otherwise be an issue if a glibc-target toolchain is used for > a freestanding kernel compilation). The case of people calling > __builtin_memcmp (or declaring memcmp themselves) without string.h > included probably isn't one it's important to optimize. The header-less case looks relevant to C++ and other language front ends, though. So a GCC_GLIBC_VERSION_GTE_IFELSE check could still make sense for them. (Dropping libc-coord.) Thanks, Florian