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 6A5063858D32 for ; Thu, 27 Apr 2023 09:23:06 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 6A5063858D32 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=1682587386; 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=2NwgyHqg50UylDBuiJ4o35D3vuqXlqAJe/welKAWNPs=; b=CxB6D8aN8t7rvv10HbEhxBcA3kexSuJoa5TlP5HiGmb+DAPHlMOqkJoh6y5sj+Olnjfzol 01Vb36xUdXck16fH922P18/BjyGO9JMA3+D3hFLdgOuD5x8M4BaKKlturZn11eqxgsVeFD RCj1aVcVL9DayzT7EvHqsEb/NLe7w1k= 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-212-4QRR4ZcqOFu5mBCLbtgWMw-1; Thu, 27 Apr 2023 05:23:04 -0400 X-MC-Unique: 4QRR4ZcqOFu5mBCLbtgWMw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 701323C025CE; Thu, 27 Apr 2023 09:23:04 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.194.156]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 321EF2166B41; Thu, 27 Apr 2023 09:23:04 +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 33R9Mw2q2748890 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Thu, 27 Apr 2023 11:22:58 +0200 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 33R9MvLS2748889; Thu, 27 Apr 2023 11:22:57 +0200 Date: Thu, 27 Apr 2023 11:22:57 +0200 From: Jakub Jelinek To: Helmut Zeisel Cc: gcc@gcc.gnu.org Subject: Re: GCC 13.1 compile error when using CXXFLAGS=-std=c++20 Message-ID: Reply-To: Jakub Jelinek References: MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 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_NUMSUBJECT,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=no 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, Apr 27, 2023 at 11:09:19AM +0200, Helmut Zeisel via Gcc wrote: > I compiled GCC 13.1.0 with GCC 12 and had the environment variable CXXFLAGS set to -std=c++20 > This gives the error (both linux and cygin) > > gcc-13.1.0/libstdc++-v3/src/c++98/bitmap_allocator.cc:51:23: error: ISO C++17 does not allow dynamic exception specifications > 51 | _M_get(size_t __sz) throw(std::bad_alloc) > > After > > unset CXXFLAGS > > compilation works Don't do it. libstdc++ carefully decides which parts of it should be compiled by which C++ standard version. By forcing it to use something it wasn't designed to work with you are breaking its assumptions. Obviously c++98 code can use C++98 features... Jakub