From owner-sc22wg14+sc22wg14-domo2=www.open-std.org@open-std.org Thu Mar 20 14:21:01 2025 Return-Path: X-Original-To: sc22wg14-domo2 Delivered-To: sc22wg14-domo2@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id 7CD96356895; Thu, 20 Mar 2025 14:21:01 +0100 (CET) Delivered-To: sc22wg14@open-std.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by www.open-std.org (Postfix) with ESMTP id 07E04356682 for ; Thu, 20 Mar 2025 14:21:00 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1742476859; 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=vzBi3teBVa4bt9+hVezmYmmZneKxr/17PDbjn5UM9GQ=; b=BwZplmqgMMd/g95065iXiSPQUsVMLKmpY+WirgE8G4eFjqzki60/r3EZHTMwUoYJGXtJkQ ZZv2k97DdN3RpuAIyYH/vupb5a6X6MaN8SAYfUw19HORl40/ylfk1A4bizdBrGO4dFuy/6 RoXN0JndyUX3x0TqHN5poN/sv87QyOo= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-410-5GfL7BikNM6PFcOK0Opicw-1; Thu, 20 Mar 2025 09:20:58 -0400 X-MC-Unique: 5GfL7BikNM6PFcOK0Opicw-1 X-Mimecast-MFC-AGG-ID: 5GfL7BikNM6PFcOK0Opicw_1742476857 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-43d08915f61so4953095e9.2 for ; Thu, 20 Mar 2025 06:20:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1742476857; x=1743081657; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=FsE5Csa5EMU360E4ONBege1iAHBB2SPQMPdKbylSmCM=; b=GmLLTIMqEBPeAOnAJE9u2Sk3l4auBlcomZZHVMw0hZuOjwQ6ivZIOIoDVxEsXvw217 1Eho3Gzmf8QHZj/nfIZrvROQj2WvfSf1bF1SDYa06t7XMSOdnfaZ4w7L9bd6DBd4q5tx ysDaTVt/5I/8vn8wFiUqQT3CeCwEaBLEQCrYmYvTWlTYICkWTmZwowFbHW9GG1Gms59c 54lUH/vB3fU2RFljIqOp8urdPzinknX4CJAw7Tt/NPcGyRXjqjnsQtFCMK7a6VvSYvWL b8tgYg1Rh5pran7hDkXMJ9XMrpi4Rxycp3ePSXnnoxD0i4Bs5Vez8pBmfTxXlvXYwPKM Ikew== X-Forwarded-Encrypted: i=1; AJvYcCWfRREXGkL4FkKPBtDkkgTIJcwc6H9UOoVMaWHfGgtfKEZ5p2J5rA5PX+1xk0Ni2Floqe8DCe6KiA==@open-std.org X-Gm-Message-State: AOJu0YxmaLRolBTTp9I78UDpmmoUbs338HRF45MCUr4wKlcMcpSUpkQp 2xI270B1DQfNNPyxFQ3lGj+lntho28skH9r4UxsDPVKeLTLInX+o/w/I7mCcM/nsFt0OXZGiJmy eM7bdnhAVmsQ+8gfjhdlyRtPaNs4uS6LFI5xbGmOT07ZaguprVLo8 X-Gm-Gg: ASbGncvwkwukY6KwPpMWaeShPPVuHwKVSa72XqEIFsx5AqOSaGoOjauFYxylM9RnSAB aLiIigpKiR6G2jlW80M4H2wBwKPiRyViLzPR5Ez+0lldDMnY5h203a19yr0n50JPl8bSpRm7mv+ nXKrR0wIHorUyJP/ZOuoSbrFEmt2W5u+JARzCjLmsXpgsa6/d5q67r7yH3nEsmOkF0lHV6wPZu9 jtyB9kvCpE2G79Bb2F2p5giGYQtX7ffW2UEuC+SKXrISsNJn9FpWN4RoUrk6mJhdDZU15n0ylOd qfwHWcsHQairtfI1jsA52FyCGjbvbdSJU0AnSPJusZW2bDA= X-Received: by 2002:a05:600c:1c03:b0:43c:fc04:6d48 with SMTP id 5b1f17b1804b1-43d4942412fmr28430035e9.0.1742476856806; Thu, 20 Mar 2025 06:20:56 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFqlDpzbDncrwrYfdwKNubGh2QqnApnG2IzQF6CGs/nF2nL/eZVONpjT2wPD8AOe5HN5aLzRw== X-Received: by 2002:a05:600c:1c03:b0:43c:fc04:6d48 with SMTP id 5b1f17b1804b1-43d4942412fmr28429695e9.0.1742476856341; Thu, 20 Mar 2025 06:20:56 -0700 (PDT) Received: from digraph.polyomino.org.uk (digraph.polyomino.org.uk. [2001:8b0:bf73:93f7::51bb:e332]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43d43f33237sm48640885e9.4.2025.03.20.06.20.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Mar 2025 06:20:55 -0700 (PDT) Received: from jsm28 (helo=localhost) by digraph.polyomino.org.uk with local-esmtp (Exim 4.97) (envelope-from ) id 1tvFpO-0000000C2Al-0wnH; Thu, 20 Mar 2025 13:20:54 +0000 Date: Thu, 20 Mar 2025 13:20:54 +0000 (UTC) From: Joseph Myers To: =?UTF-8?Q?J=E2=82=91=E2=82=99=E2=82=9B_Gustedt?= cc: Robert Seacord , "sc22wg14@open-std. org" Subject: Re: [SC22WG14.29934] 30 DAY REVIEW N3517 Gustedt, Array subscripting without decay v7 In-Reply-To: <20250320103716.923FA3568E3@www.open-std.org> Message-ID: References: <20250319173407.EDB283568EB@www.open-std.org> <20250319175258.58C4A3568EB@www.open-std.org> <20250320103716.923FA3568E3@www.open-std.org> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: hmZA6ObznkV0KbWLTkGmL0c3uk8DJumFAxvP2nAZ9T4_1742476857 X-Mimecast-Originator: redhat.com Content-Type: multipart/mixed; boundary="-1152306461-1008947481-1742476854=:2858159" Sender: owner-sc22wg14@open-std.org Precedence: bulk This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---1152306461-1008947481-1742476854=:2858159 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Thu, 20 Mar 2025, Jā‚‘ā‚™ā‚› Gustedt wrote: > (1) unqualified, which for the standard covers only `const`, > `volatile` and `restrict` > > (2) non-atomic, which is a can of worms > > For (1) I think that our paper is correct, because anyhow such an > "rvalue object" is a copy of some sort, and this is what we have done > for now, anyhow. The question with arrays, outside of typeof, is for example whether struct s { const int a[2][2]; } x; void f1() { if (0) *((0, x).a[1] + 1) = 1; } void f2() { if (0) *(*((0, x).a + 1) + 1) = 1; } should involve constraint violations (assignment to const int) versus runtime UB (which doesn't actually occur because it's inside if (0)). With the wording I proposed in issue 1001, the array and its members keep the qualified type even as part of the rvalue structure (0, x), and the type only becomes unqualified when producing a non-array rvalue. So both f1 and f2 involve constraint violations; the arrays decay to pointers to const. I think this proposal would remove the constraint for f1 only, by giving (0, x).a[1] the type int[2] rather than const int[2]. -- Joseph S. Myers josmyers@redhat.com ---1152306461-1008947481-1742476854=:2858159--