220 11896 article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: N4078: Rvalue reference overloads for value() method returns object by value Date: Sat, 12 Jul 2014 23:23:36 +0800 Lines: 80 Approved: news@gmane.org Message-ID: References: <4DA018C3-2327-4F55-B7F8-7988EC7B789A@gmail.com> <1a858a77-310b-4591-aaf5-960c40d9f5fc@isocpp.org> <66AF41C1-CB37-4311-98EA-D47DBC6068DC@gmail.com> <66c38b61-7a95-4ace-b34f-2346bb334fb9@isocpp.org> <6F4B3C72-9962-48DC-8527-0C89EA1B9710@gmail.com> <35873CE5-ED8C-4C03-A6A1-E4132DECD91F@gmail.com> <335948E6-8140-4673-B958-930356A52070@gmail.com> <76ACA175-5A44-4BE8-B49F-BAC6DA65E6B1@gmail.com> <4D3852AD-1AEB-44BA-941C-D645BAD19405@gmail.com> <6a4b6425-1167-40c1-acd8-3945c8cd4c74@isocpp.org> <13DD0D7A-A146-4667-9F30-6FB3739CDBE0@gmail.com> <6B925FF7-2940-44C7-BF1D-13209A703BA2@gmail.com> <944C9C01-865B-4215-8C91-95F01AEA256E@gmail.com> <8DC3E474-3957-40B2-B492-D4AF2FDDD451@gmail.com> <0ACAE525-4FB2-4932-BBD2-F0623C4EBBFB@gmail.com> <52187852-ff8e-4e59-a8cf-7a29fd0a405b@isocpp.org> <8209A2E9-D947-4C00-A1F3-38F5676A4E52@gmail.com> <4c42f7c9-0588-4ab9-9af5-b2e692513993@isocpp.org> <225BBAAC-B3FA-4014-9FB6-64C48DF4208E@gmail.com> <1b70888c-eb6a-49e5-b254-a475ef015570@isocpp.org> <6CFC366C-D196-4A2E-B4EE-D1E6B26AE6C0@gmail.com> <3baba983-4d62-4887-a969-020ecf027a45@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: multipart/alternative; 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Sat, 12 Jul 2014 08:24:01 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4001:c03::229 as permitted sender) client-ip=2607:f8b0:4001:c03::229; Original-Received: by mail-ie0-f169.google.com with SMTP id tp5so1907440ieb.0 for ; Sat, 12 Jul 2014 08:24:01 -0700 (PDT) X-Received: by 10.43.104.132 with SMTP id dm4mr11543288icc.56.1405178641549; Sat, 12 Jul 2014 08:24:01 -0700 (PDT) Original-Received: from [172.20.10.2] ([121.54.54.34]) by mx.google.com with ESMTPSA id jf5sm6368772igb.2.2014.07.12.08.23.59 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 12 Jul 2014 08:24:01 -0700 (PDT) In-Reply-To: <3baba983-4d62-4887-a969-020ecf027a45@isocpp.org> X-Mailer: Apple Mail (2.1878.6) X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4001:c03::229 as permitted sender) smtp.mail=potswa@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=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-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:11896 Archived-At: --Apple-Mail=_FDCA0442-3931-4935-B9D3-C87EA8CBF473 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=ISO-8859-1 On 2014-07-12, at 8:57 PM, tomaszkam@gmail.com wrote: > This will introduce a lot of temporaries in the code. Most code tends to have a lot of temporaries anyway. Temporaries are a prod= uct of value semantics, as opposed to reference semantics. Since rvalue ref= erences introduce concerns of aliasing and referent lifetime, I think the l= anguage should have the programmer mention std::move or std::forward when t= hey are in effect, and specifically for the thing being referenced, not onl= y its container. No proposal from me will necessitate more temporaries :) . I like performan= ce as much as anyone, but only within the limits of safety. As for the rest, I think you're reading too much into the differences. The = dilemma is between two different, equally expressive, conventions favoring = references or values. Performance and safety are both possible with either. --=20 ---=20 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 e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --Apple-Mail=_FDCA0442-3931-4935-B9D3-C87EA8CBF473 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1
On 2014&= ndash;07–12, at 8:57 PM, tomas= zkam@gmail.com wrote:

This will in= troduce a lot of temporaries in the code.
Most code tends to have a lot of temporaries anyway. Temporarie= s are a product of value semantics, as opposed to reference semantics. Sinc= e rvalue references introduce concerns of aliasing and referent lifetime, I= think the language should have the programmer mention std::move or std::fo= rward when they are in effect, and specifically for the thing being referen= ced, not only its container.

No proposal from me w= ill necessitate more temporaries :) . I like performance as much as anyone,= but only within the limits of safety.

As for the rest,= I think you’re reading too much into the differences. The dilemma is= between two different, equally expressive, conventions favoring references= or values. Performance and safety are both possible with either.

--

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