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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id AEDBA3854547 for ; Fri, 18 Nov 2022 07:48:39 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org AEDBA3854547 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=1668757719; 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=HCEA/KZuk4XosGNUewKJfAZwEQsu5A5xw86Bw36qSZA=; b=aVxJ7B9rqc/X9T3FJz/tBGpMFc2D8X9BOWcFBaIy33bVOAF7yVViMMEsNHIfddlXGmabgg d4oTMEWn2I1srrs8c3qu2NG7EHzRKYVOSftm4kYCFqOvLSgqHMuPrpCHHpKlwpDMdx6fqP QmF1HcPKmjQQHIVzNc3uQQexuuBsJ+0= 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-312-Ro-s5JBOMjmOkAUxaf-KkA-1; Fri, 18 Nov 2022 02:48:38 -0500 X-MC-Unique: Ro-s5JBOMjmOkAUxaf-KkA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C4EA41C0514A for ; Fri, 18 Nov 2022 07:48:37 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 779C71121325; Fri, 18 Nov 2022 07:48:37 +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 2AI7mW9T1888552 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 18 Nov 2022 08:48:33 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 2AI7mW661888551; Fri, 18 Nov 2022 08:48:32 +0100 Date: Fri, 18 Nov 2022 08:48:32 +0100 From: Jakub Jelinek To: Jason Merrill , Marek Polacek Cc: Jonathan Wakely , gcc-patches@gcc.gnu.org Subject: Re: [PATCH] c++, v4: Implement C++23 P2647R1 - Permitting static constexpr variables in constexpr functions Message-ID: Reply-To: Jakub Jelinek References: <016f168b-f143-baff-5f71-c48d4611ae11@redhat.com> <740b5e1e-7143-c291-5594-af937867fbc3@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 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=-3.9 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: On Thu, Nov 17, 2022 at 07:15:05PM -0500, Marek Polacek wrote: > > --- gcc/cp/decl.cc.jj 2022-11-16 14:44:43.692339668 +0100 > > +++ gcc/cp/decl.cc 2022-11-17 20:53:44.102011594 +0100 > > @@ -5600,6 +5600,57 @@ groktypename (cp_decl_specifier_seq *typ > > return type; > > } > > > > +/* For C++17 and older diagnose static or thread_local decls in constexpr > > + or consteval functions. For C++20 similarly, except if they are > > In C++17 we don't support consteval so I guess drop the "or consteval "? I just forgot to update the function comment. Anyway, I think: > BTW, I notice that the patch breaks > g++.dg/cpp1y/lambda-generic-func1.C > g++.dg/cpp1z/constexpr-lambda16.C > Maybe they just need dg- tweaks. this is actually a real bug and I'm not sure how to resolve that. We have there: int main() { [](auto i) { if (i) { int j; static int k; return i + j; } return i; }(0); } and for C++17/20 I presume something (haven't figured out yet what) marks the lambda operator() when still a template as constexpr and then cp_finish_decl -> diagnose_static_in_constexpr pedwarns on it. For the above perhaps we could figure out there is a static int k; in the operator() and don't turn it into constexpr, but what if there is something that would e.g. satisfy decl_maybe_constant_var_p but not decl_constant_var_p when actually instantiated? Without my patch, the diagnostics is in start_decl which isn't called again during instantiation, so I presume we mark it as constexpr and then we'd diagnose it during constant evaluation. Jakub