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 7CE5C397282F for ; Wed, 3 Mar 2021 17:15:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 7CE5C397282F 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-473-9liieGhDPdC0qVwq3vPtuw-1; Wed, 03 Mar 2021 12:15:01 -0500 X-MC-Unique: 9liieGhDPdC0qVwq3vPtuw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6AD42107ACC7; Wed, 3 Mar 2021 17:15:00 +0000 (UTC) Received: from localhost (unknown [10.33.37.30]) by smtp.corp.redhat.com (Postfix) with ESMTP id ED3D85D736; Wed, 3 Mar 2021 17:14:59 +0000 (UTC) Date: Wed, 3 Mar 2021 17:14:59 +0000 From: Jonathan Wakely To: Thiago Macieira Cc: Ville Voutilainen , Thomas Rodgers , libstdc++ Subject: Re: C++2a synchronisation inefficient in GCC 11 Message-ID: References: <1968544.UC5HiB4uFJ@tjmaciei-mobl1> <20210303143020.GR3008@redhat.com> <5422241.zR2LmqfNYo@tjmaciei-mobl1> MIME-Version: 1.0 In-Reply-To: <5422241.zR2LmqfNYo@tjmaciei-mobl1> X-Clacks-Overhead: GNU Terry Pratchett X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, KAM_NUMSUBJECT, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libstdc++@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++ mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Mar 2021 17:15:06 -0000 On 03/03/21 09:07 -0800, Thiago Macieira via Libstdc++ wrote: >On Wednesday, 3 March 2021 06:30:20 PST Jonathan Wakely wrote: >> Yes, exactly. They could still do that if some additional option/macro >> was needed to get to those new facilities though. >> >> My concern is that if we add a new "I know what I'm doing" option, >> everybody defines it (because that's what blog posts and youtube >> videos and conference talks tell them to do, because that gives them >> the new shiny things) and then it just becomes a default. >> >> Maybe Qt wouldn't define it, but plenty would. > >Well, if you define the "void warranty" option and you break things, you get >to keep both pieces. > >Another option is to fiddle with the include path. > >$ gcc -v -E -xc++ /dev/null >Using built-in specs. >[...] >#include <...> search starts here: > /usr/lib64/gcc/x86_64-generic-linux/10/../../../../include/c++/10 > /usr/lib64/gcc/x86_64-generic-linux/10/../../../../include/c++/10/x86_64- >generic-linux > /usr/lib64/gcc/x86_64-generic-linux/10/../../../../include/c++/10/backward > /usr/lib64/gcc/x86_64-generic-linux/10/include > /usr/local/include > /usr/lib64/gcc/x86_64-generic-linux/10/include-fixed > /usr/include > >That "backward" has always got me thinking. What if we had a command-line >option like -fexperimental-c++ option that added the $CXXROOT/experimental We already have an experimental sub-dir for TS headers, so you need to pick another name. Otherwise and get mixed up.