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 34E4F383234B for ; Wed, 16 Nov 2022 14:08:52 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 34E4F383234B 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=1668607731; 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=3XZK8f8Voj6/AJ8yUd/I4buDRqRWLMPLTpede4jKsjg=; b=M71mDwg8Wd/6hFpOpe0QlUeNLk43JYOndxMqLuzaHP7AK5k0Vm2fDNzKqmXaxWwU3fD9PP xUy30La77nlkfOCAKKnSl0TvDpr73yf2M01+VfNF1Q1MqY0kNiUjaqcq6wvZliWhMQXkIt 0zcjG/TDwF9p+waIjK3hkd954SriMB8= 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-133-IAhtmWPdMdStMMExK4gsvg-1; Wed, 16 Nov 2022 09:08:48 -0500 X-MC-Unique: IAhtmWPdMdStMMExK4gsvg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A9D708C47AD for ; Wed, 16 Nov 2022 14:08:33 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.193.99]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 29AB7C2C8C7; Wed, 16 Nov 2022 14:08:33 +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 2AGE8SWD2465645 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 16 Nov 2022 15:08:28 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 2AGE8RlS2465644; Wed, 16 Nov 2022 15:08:27 +0100 Date: Wed, 16 Nov 2022 15:08:27 +0100 From: Jakub Jelinek To: Jason Merrill Cc: Jonathan Wakely , 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 10.11.54.8 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 08:20:34AM -0500, Jason Merrill wrote: > > 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. > > Indeed, though the hypothetical C++20 change could still use the "usable in > constant expressions" phrase. Yes. Though, with -std=c++20 we are rejected already in start_decl's if (current_function_decl && VAR_P (decl) && DECL_DECLARED_CONSTEXPR_P (current_function_decl) && cxx_dialect < cxx23) { bool ok = false; if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl)) error_at (DECL_SOURCE_LOCATION (decl), "%qD defined % in %qs function only " "available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl, DECL_IMMEDIATE_FUNCTION_P (current_function_decl) ? "consteval" : "constexpr"); else if (TREE_STATIC (decl)) error_at (DECL_SOURCE_LOCATION (decl), "%qD defined % in %qs function only available " "with %<-std=c++2b%> or %<-std=gnu++2b%>", decl, DECL_IMMEDIATE_FUNCTION_P (current_function_decl) ? "consteval" : "constexpr"); else ok = true; if (!ok) cp_function_chain->invalid_constexpr = true; } and at that point I fear decl_maybe_constant_var_p will not work properly. Shall this hunk be moved somewhere else (cp_finish_decl?) where we can already call it, or do the above in start_decl for cxx_dialect < cxx20 and add a cxx_dialect == cxx20 hunk in cp_finish_decl? Jakub