220 35685 article Path: news.gmane.org!.POSTED!not-for-mail From: Jake Arkinstall Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Rotational shift operator Date: Thu, 30 Nov 2017 23:12:37 +0000 Lines: 91 Approved: news@gmane.org Message-ID: References: <69593098-e2cc-487e-bd14-9001b27aa7c1@isocpp.org> <8575602.V2okVmv5xV@tjmaciei-mobl1> <1856787.AgLzTjE61K@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a113db2c6618275055f3b635d" X-Trace: blaine.gmane.org 1512083559 8648 195.159.176.226 (30 Nov 2017 23:12:39 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 30 Nov 2017 23:12:39 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDCZX3WUUQFRBZ5AQLIQKGQEOA7I36I@isocpp.org Fri Dec 01 00:12:35 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 1eKY0Q-0001tk-Oj for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id c136sor1719503oih.283.2017.11.30.15.12.39 for (Google Transport Security); Thu, 30 Nov 2017 15:12:39 -0800 (PST) Received-SPF: pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.202.73.144 with SMTP id w138mr5901762oia.213.1512083558595; Thu, 30 Nov 2017 15:12:38 -0800 (PST) Original-Received: by 10.168.69.140 with HTTP; Thu, 30 Nov 2017 15:12:37 -0800 (PST) Original-Received: by 10.168.69.140 with HTTP; Thu, 30 Nov 2017 15:12:37 -0800 (PST) In-Reply-To: X-Original-Sender: jake.arkinstall@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=MZd039Oj; spf=pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jake.arkinstall@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-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:35685 Archived-At: --001a113db2c6618275055f3b635d Content-Type: text/plain; charset="UTF-8" On 30 Nov 2017 22:42, "Hyman Rosen" wrote: The premise that got C++ off the ground was its backwards-compatibility. It was C with Classes, you could gain the benefits of the bits you used and your plain old C code would keep working fine. Those days are long gone - and good riddance to them. People have better things to do than to go chasing down problems in old systems because the new shiny decided to break them. This is why we have versioning. If you have an old system that fails because it relied on one compiler's approach to an undefined behaviour, you have absolutely NO contract with the compiler such that later versions will accommodate your shoddy code. If you want undefined behaviour to remain the same, keep the same compiler. Ada's handling of undefined behaviour sounds like it adds overhead (in the form of branching). Maybe I'm wrong, as I don't know Ada. I see what you're getting at though. For the record, a C++ implementation is perfectly welcome to detect undefined behaviour and handle it exactly in this way - as the behaviour is undefined, the compiler can do with it what it wants. With a less newbie friendly compiler, though, the focus will be on making assumptions that you're operating within defined bounds in order to perform some optimisation. -- 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/CAC%2B0CCONyHq-Pxx_cG8zgohBYy4Q6ARJGBUCPszDuHzMFOuXJw%40mail.gmail.com. --001a113db2c6618275055f3b635d Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On 30 Nov 2017 22:42, "Hyman Rosen" <hyman.rosen@gmail.com> wrote:
The pre= mise that got C++ off the ground was its backwards-compatibility.
It was C with Classes, you could gain the benefits of the bits you used an= d
your plain old C code would keep working fine.
=

Those days are long gone - and go= od riddance to them.

Peo= ple have better things to do than to go chasing down problems in old
sys= tems because the new shiny decided to break them.

This i= s why we have versioning. If you have an old system that fails because it r= elied on one compiler's approach to an undefined behaviour, you have ab= solutely NO contract with the compiler such that later versions will accomm= odate your shoddy code. If you want undefined behaviour to remain the same,= keep the same compiler.

Ada's handling of undefined behaviour sounds like it adds overhead (in= the form of branching). Maybe I'm wrong, as I don't know Ada. I se= e what you're getting at though. For the record, a C++ implementation i= s perfectly welcome to detect undefined behaviour and handle it exactly in = this way - as the behaviour is undefined, the compiler can do with it what = it wants. With a less newbie friendly compiler, though, the focus will be o= n making assumptions that you're operating within defined bounds in ord= er to perform some optimisation.

--
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To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit h= ttps://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAC%2B0CCONyHq-= Pxx_cG8zgohBYy4Q6ARJGBUCPszDuHzMFOuXJw%40mail.gmail.com.
--001a113db2c6618275055f3b635d-- .