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 DA20F3954C41 for ; Wed, 16 Nov 2022 06:20:01 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org DA20F3954C41 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=1668579601; 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=MjV1pmk20lOtvyWk1KABJO2VdxZYlokiVkrkTYQ+cNQ=; b=BFRzM/R/ZXm71U7XUKrXBgzG6qwVoXk+DBgsh19tHJbkFDrTs52AqUsxTty1w12mWZLRBh mEmQHpGdIAbMU/Z+OaQt/hqxufclOrvwk6GfkVjHr8uDTwsu4UhhDV6Oh3S2qafQnLgcX0 DJYKlXs2Q0zJyy8tq/zJJQIQjfOIUxU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-551-7KFMA6AFN6aH6hCrFu6jbA-1; Wed, 16 Nov 2022 01:19:56 -0500 X-MC-Unique: 7KFMA6AFN6aH6hCrFu6jbA-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 7FA47811E75 for ; Wed, 16 Nov 2022 06:19:56 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.38]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 361F940C845A; Wed, 16 Nov 2022 06:19:56 +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 2AG6Jpk12448321 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 16 Nov 2022 07:19:51 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 2AG6Jo972448320; Wed, 16 Nov 2022 07:19:50 +0100 Date: Wed, 16 Nov 2022 07:19:50 +0100 From: Jakub Jelinek To: Jason Merrill , Jonathan Wakely Cc: gcc-patches@gcc.gnu.org, Marek Polacek Subject: Re: [PATCH] c++, v2: Implement C++23 P2647R1 - Permitting static constexpr variables in constexpr functions Message-ID: Reply-To: Jakub Jelinek References: MIME-Version: 1.0 In-Reply-To: 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; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-3.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,KAM_SHORT,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 Wed, Nov 16, 2022 at 12:27:02AM +0000, Jonathan Wakely wrote: > On Tue, 15 Nov 2022 at 23:50, Jakub Jelinek wrote: > > > > On Tue, Nov 15, 2022 at 06:36:38PM -0500, Jason Merrill wrote: > > > > Here is an updated patch that passed bootstrap/regtest, the only > > > > change is another testcase tweak. > > > > > > > > 2022-11-13 Jakub Jelinek > > > > > > > > gcc/c-family/ > > > > * c-cppbuiltin.cc (c_cpp_builtins): Bump __cpp_constexpr > > > > value from 202207L to 202211L. > > > > gcc/cp/ > > > > * constexpr.cc (cxx_eval_constant_expression): Implement C++23 > > > > P2647R1 - Permitting static constexpr variables in constexpr functions. > > > > Allow decl_maybe_constant_var_p static or thread_local vars for > > > > C++23. > > > > > > This was accepted as a DR, so it shouldn't be limited to C++23 mode. > > > Certainly it should be allowed in C++20 mode; I don't have a strong opinion > > > about C++14/17. Jonathan, do you? > > > > How will a feature with feature test macro with multiple values work as DR? > > Or will everything but the macro be treated as a DR (so __cpp_constexpr >= > > 202211L only for C++23)? > > Yes, I think so. We just won't be able to advertise this feature as > supported in C++20. Ok. But there is another issue, the https://eel.is/c++draft/expr.const#5.2 spot that P2647R1 is changing didn't exist in C++20, it was only added with P2242R3. So, if one would treat P2647R1 as a DR for C++20, one has to come up with a different standard modification. Probably change the last bullet of: [dcl.constexpr]/3 its function-body shall not enclose a goto statement, an identifier label, a definition of a variable of non-literal type or of static or thread storage duration. to a definition of a variable of non-literal type or of a non-constexpr variable of static or thread storage duration. or so. Jakub