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 BC4663853D45 for ; Thu, 17 Nov 2022 18:42:48 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org BC4663853D45 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=1668710568; 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=5HG+IOw18zY703/kxzIOpw6xKih/bf7zfDWspP4Q+Yc=; b=MlWCwUiHZ/DKizWjWVvWUKQPehCNo8fvPscCiE6OUZ7/Zi1IMT2AB/bpAxoBSm3IcxB18y GkHwN/Kr1Rdn75xdet3/XG9ZxsASCwzRpYppUaqGsk95c32oiIExpkR49f3EttEaG2DlJA g8JTkYQ/ELSldK+UIguo1JU8C+aX6P4= 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-439-bkhmY1pnNsOfqxIq2i0RhA-1; Thu, 17 Nov 2022 13:42:46 -0500 X-MC-Unique: bkhmY1pnNsOfqxIq2i0RhA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 328E538012DB for ; Thu, 17 Nov 2022 18:42:46 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D7306492B04; Thu, 17 Nov 2022 18:42:45 +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 2AHIgfNX014076 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 17 Nov 2022 19:42:41 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 2AHIgeRw014075; Thu, 17 Nov 2022 19:42:40 +0100 Date: Thu, 17 Nov 2022 19:42:40 +0100 From: Jakub Jelinek To: Jason Merrill Cc: Jonathan Wakely , gcc-patches@gcc.gnu.org, Marek Polacek Subject: Re: [PATCH] c++, v3: 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: <740b5e1e-7143-c291-5594-af937867fbc3@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 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 09:42:18AM -0500, Jason Merrill wrote: > > --- gcc/cp/constexpr.cc.jj 2022-11-17 08:48:30.530357181 +0100 > > +++ gcc/cp/constexpr.cc 2022-11-17 09:56:50.479522863 +0100 > > @@ -7098,7 +7098,8 @@ cxx_eval_constant_expression (const cons > > && (TREE_STATIC (r) > > || (CP_DECL_THREAD_LOCAL_P (r) && !DECL_REALLY_EXTERN (r))) > > /* Allow __FUNCTION__ etc. */ > > - && !DECL_ARTIFICIAL (r)) > > + && !DECL_ARTIFICIAL (r) > > + && (cxx_dialect < cxx20 || !decl_constant_var_p (r))) > > I don't think we need to check cxx_dialect here since > diagnose_static_in_constexpr will have already complained. I thought for older C++ this is to catch void foo () { constexpr int a = ({ static constexpr int b = 2; b; }); } and for C++23 the only 3 spots that diagnose those. But perhaps for C++20 or older we can check if the var has a context of a constexpr function (then assume cp_finish_decl errored or pedwarned already) and only error or pedwarn otherwise. > > > { > > if (!ctx->quiet) > > { > > @@ -9588,7 +9589,12 @@ potential_constant_expression_1 (tree t, > > tmp = DECL_EXPR_DECL (t); > > if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp)) > > { > > - if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp)) > > + if (CP_DECL_THREAD_LOCAL_P (tmp) > > + && !DECL_REALLY_EXTERN (tmp) > > + && (cxx_dialect < cxx20 > > + || (processing_template_decl > > + ? !decl_maybe_constant_var_p (tmp) > > + : !decl_constant_var_p (tmp)))) > > Or here. > > > { > > if (flags & tf_error) > > constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p, > > @@ -9596,7 +9602,11 @@ potential_constant_expression_1 (tree t, > > "% context", tmp); > > return false; > > } > > - else if (TREE_STATIC (tmp)) > > + else if (TREE_STATIC (tmp) > > + && (cxx_dialect < cxx20 > > + || (processing_template_decl > > + ? !decl_maybe_constant_var_p (tmp) > > + : !decl_constant_var_p (tmp)))) > > { > > if (flags & tf_error) > > constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p, And these too. > > +static void > > +diagnose_static_in_constexpr (tree decl) > > +{ > > + if (current_function_decl && VAR_P (decl) > > + && DECL_DECLARED_CONSTEXPR_P (current_function_decl) > > + && cxx_dialect < cxx23 > > + && (cxx_dialect < cxx20 > > + || (processing_template_decl > > + ? !decl_maybe_constant_var_p (decl) > > + : !decl_constant_var_p (decl)))) > > For (maybe) constant variables let's make this error a pedwarn in C++20 and > below. Ok. > > > + { > > + 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; > > + } > > +} > > + > > /* Process a DECLARATOR for a function-scope or namespace-scope > > variable or function declaration. > > (Function definitions go through start_function; class member > > @@ -5860,28 +5895,8 @@ start_decl (const cp_declarator *declara > > DECL_THIS_STATIC (decl) = 1; > > } > > - 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; > > - } > > + if (cxx_dialect < cxx20) > > + diagnose_static_in_constexpr (decl); > > Can we drop this call (and make the ones in cp_finish_decl unconditional)? Yes, will do it. Jakub