220 36357 <83d8a425-fd2f-41b6-9941-2a5deb27806d@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Sub-objects and their copy ellision Date: Tue, 26 Dec 2017 07:25:27 -0800 (PST) Lines: 83 Approved: news@gmane.org Message-ID: <83d8a425-fd2f-41b6-9941-2a5deb27806d@isocpp.org> References: <1c6eff77-d71f-4dd7-8c13-f609460a03f0@isocpp.org> <3ec0bd22-b228-4026-bb49-aec5102918c7@isocpp.org> <924751e5-c880-42aa-95ab-99ef1050be2e@isocpp.org> <80bbb75a-2a62-537a-3733-898225325a41@technion.ac.il> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_13377_1142503506.1514301927407" X-Trace: blaine.gmane.org 1514301811 9644 195.159.176.226 (26 Dec 2017 15:23:31 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 26 Dec 2017 15:23:31 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBB2GTRHJAKGQEMEQAFKI@isocpp.org Tue Dec 26 16:23:27 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f199.google.com ([209.85.217.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eTr4h-00029B-0x for gclcip-std-proposals@m.gmane.org; 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Tue, 26 Dec 2017 07:25:29 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.159.45.148 with SMTP id v20ls260549uaj.2.gmail; Tue, 26 Dec 2017 07:25:28 -0800 (PST) X-Received: by 10.31.2.144 with SMTP id 138mr2375948vkc.5.1514301928018; Tue, 26 Dec 2017 07:25:28 -0800 (PST) In-Reply-To: <80bbb75a-2a62-537a-3733-898225325a41@technion.ac.il> X-Original-Sender: jmckesson@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:36357 Archived-At: ------=_Part_13377_1142503506.1514301927407 Content-Type: multipart/alternative; boundary="----=_Part_13378_1409979297.1514301927407" ------=_Part_13378_1409979297.1514301927407 Content-Type: text/plain; charset="UTF-8" On Tuesday, December 26, 2017 at 4:05:52 AM UTC-5, Eyal Rozenberg wrote: > > On 12/25/17 8:15 PM, Nicol Bolas wrote: > > On Monday, December 25, 2017 at 1:12:19 PM UTC-5, Antony Polukhin wrote: > > Why is this circumstance important enough to be /worth/ all of this > hassle? > > Because right now compilers are entirely-or-partially prevented from > applying a useful optimization in some relatively-common cases. > I see little evidence that these cases are indeed "relatively-common" enough to bother with this. > Then why take the time to change the standard to allow it? > > Because now it (seems to) prevent it, and definitely doesn't encourage it. > Right, but that wasn't my question. My question was why we should take the time to standardize something that's such a corner case. That compilers can only apply such an optimization when the stars align just right. -- 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/83d8a425-fd2f-41b6-9941-2a5deb27806d%40isocpp.org. ------=_Part_13378_1409979297.1514301927407 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Tuesday, December 26, 2017 at 4:05:52 AM UTC-5, Eyal Ro= zenberg wrote:
On 12/25/17 8:15= PM, Nicol Bolas wrote:
> On Monday, December 25, 2017 at 1:12:19 PM UTC-5, Antony Polukhin = wrote:
> Why is this circumstance important enough to be /worth/ all of thi= s hassle?

Because right now compilers are entirely-or-partially prevented from
applying a useful optimization in some relatively-common cases.

I see little evidence that these cases are ind= eed "relatively-common" enough to bother with this.
> Then why take the = time to change the standard to allow it?

Because now it (seems to) prevent it, and definitely doesn't encour= age it.

Right, but that wasn't my q= uestion. My question was why we should take the time to standardize somethi= ng that's such a corner case. That compilers can only apply such an opt= imization when the stars align just right.

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/83d8a425-fd2f-41b6-9941-2a5deb27806d= %40isocpp.org.
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