220 36363 article Path: news.gmane.org!.POSTED!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Default assignment operators for std::pair and std::tuple Date: Tue, 26 Dec 2017 22:11:19 +0200 Lines: 35 Approved: news@gmane.org Message-ID: References: <4110e47f-a021-4ccc-9e03-53e4ebdb8c21@isocpp.org> <4605434.q3o9RnjlYE@tjmaciei-mobl1> <5300cf40-f7db-4eb6-ad36-4742855124ae@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" X-Trace: blaine.gmane.org 1514318963 30506 195.159.176.226 (26 Dec 2017 20:09:23 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 26 Dec 2017 20:09:23 +0000 (UTC) To: "ISO C++ Standard - Future Proposals" Original-X-From: std-proposals+bncBC5JHI7A7ALRB2GZRLJAKGQEE2KMVXI@isocpp.org Tue Dec 26 21:09:19 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f69.google.com ([209.85.218.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eTvXK-0007VC-VH for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id z3sor6961688otz.69.2017.12.26.12.11.20 for (Google Transport Security); Tue, 26 Dec 2017 12:11:20 -0800 (PST) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.157.13.225 with SMTP id 88mr21579311ots.338.1514319079876; Tue, 26 Dec 2017 12:11:19 -0800 (PST) Original-Received: by 10.157.43.248 with HTTP; Tue, 26 Dec 2017 12:11:19 -0800 (PST) In-Reply-To: X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=fo3U4BOG; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=ville.voutilainen@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:36363 Archived-At: On 26 December 2017 at 21:51, mrpi via ISO C++ Standard - Future Proposals wrote: > Doesn't the same argument about optionals and variants apply? Just recently > std::optional and std::variant weren't yet made trivially copyable (nor have > any recent draft of the standard accepted it yet). What I'm asking about is > doing the same for std::pair and std::tuple. The difference is that optional and variant were introduced in C++17, and are still considered experimental by (some) implementations. Both tuple and pair have been there since C++11 or before. > And furthermore, what sort of problems would pop up from enforcing > std::tuple to be trivially copyable? No other problems besides the ABI break, I think. Implementation-wise there's nothing The Elf or his Mighty Maintainer could not do, and the same applies to other implementations and their authors; making such types conditionally trivial is not particularly hard. The warts arise because the C++11 types weren't specified or necessarily known how to write in fully-constexpr (constexpr was enhanced in C++14) or fully-triviality-reflecting fashion, and changing that, while doable in a pure C++17 environment, is not always so straightforward when C++11 (and ABI) compatibility is a concern. -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAFk2RUY3XQiLzsSTiZ6QECf7EK%3DyEoq%2B3JGA05783AgbqHVMOg%40mail.gmail.com. .