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 751F93858410 for ; Fri, 18 Nov 2022 15:03:32 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 751F93858410 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=1668783811; h=from:from: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=8GCEOWxJ4L1xDD4W0R+VntGqEKPgDN+jrD8ejHtHGFs=; b=JIUfySWY8mLLZNqmg9ZbSBHvwuGFF+vjuMH74ENP9XoXQFyD+qT16wIZHs6QLEsWM0vm5V OxOwXFNWxsJwq02xgoJtxkciB+STaSP0NHFn3tmL9XNTDGK3He5FwU+0iUsiVVwhBLiHTH sE2Zt8/d0IUp3bFhOqrHYHVM/Lv5Koo= Received: from mail-qt1-f200.google.com (mail-qt1-f200.google.com [209.85.160.200]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-192-9yzcIyZoN7acTGsUPH4nxw-1; Fri, 18 Nov 2022 10:03:22 -0500 X-MC-Unique: 9yzcIyZoN7acTGsUPH4nxw-1 Received: by mail-qt1-f200.google.com with SMTP id z11-20020a05622a028b00b003a550fa8989so5063347qtw.12 for ; Fri, 18 Nov 2022 07:03:22 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=8GCEOWxJ4L1xDD4W0R+VntGqEKPgDN+jrD8ejHtHGFs=; b=5OpQpXieRX8nWpRyjNhrw5ExI6PLMXL6nN1NZg1g6SprCztW84ojnObtOT0PVvCJBw HKU254wqp7qCTwKnPUr1cPB8f/juw0JQgh46aGPTuDB6x80JyfFZuh+inG+r7cxJLA2j GT2/40P4jUOSb1LuLHvsBvDQctinLgVuMQm8HwaF2hH/xMRqLFELK9tm9oVAlye0oxHS Xc7WWMaBV3wzERBV5HTVPYC6nQSR9oKfH+6ANLV3kLSEdyA5V4COwbepWsAVckapRJN2 br9CcLqz3cR1S01kH0C6bbw6PONV8UTwGlg2v2achedSWxcwAbpSO7UGFLkr/8IsPKxI gZWA== X-Gm-Message-State: ANoB5pkqxiCkYniTRPpaKv4jew+eA1lNsXTKQUcILhQgIQCac5/uIuSZ 5GwAfNYgjkCAlkk+lrnCeFYixFa+KxrcSCXSMG6sI7as/lalBVPD+FWf+6tB5WEw3AwF4d8bBi8 neWgHZv5fE7nsUvf1vA== X-Received: by 2002:ad4:4e65:0:b0:4b3:90da:57bd with SMTP id ec5-20020ad44e65000000b004b390da57bdmr6888621qvb.114.1668783801756; Fri, 18 Nov 2022 07:03:21 -0800 (PST) X-Google-Smtp-Source: AA0mqf5mxMiT2+4LxHY6/2FrZtH8THWM9Kzfnt+7zjGr2uQOrWWlayTYS5OWFdhfPrDpITBwUDewKw== X-Received: by 2002:ad4:4e65:0:b0:4b3:90da:57bd with SMTP id ec5-20020ad44e65000000b004b390da57bdmr6888606qvb.114.1668783801496; Fri, 18 Nov 2022 07:03:21 -0800 (PST) Received: from redhat.com (2603-7000-9500-2e39-0000-0000-0000-1db4.res6.spectrum.com. [2603:7000:9500:2e39::1db4]) by smtp.gmail.com with ESMTPSA id br35-20020a05620a462300b006cfc01b4461sm2559652qkb.118.2022.11.18.07.03.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Nov 2022 07:03:20 -0800 (PST) Date: Fri, 18 Nov 2022 10:03:18 -0500 From: Marek Polacek To: Jakub Jelinek Cc: Jason Merrill , 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: References: <016f168b-f143-baff-5f71-c48d4611ae11@redhat.com> <740b5e1e-7143-c291-5594-af937867fbc3@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.2.7 (2022-08-07) 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=-6.2 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 Fri, Nov 18, 2022 at 08:48:32AM +0100, Jakub Jelinek wrote: > 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 Right, that's the C++17 implicit constexpr for lambdas, finish_function: /* Lambda closure members are implicitly constexpr if possible. */ if (cxx_dialect >= cxx17 && LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl))) DECL_DECLARED_CONSTEXPR_P (fndecl) = ((processing_template_decl || is_valid_constexpr_fn (fndecl, /*complain*/false)) && potential_constant_expression (DECL_SAVED_TREE (fndecl))); > 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. Um, can we give up on trying to handle C++17/C++20 then? Marek