220 35631 <0a5bfe0d-0bdd-6f87-c49f-a6691963a8ff@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Andrey Semashev Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Rotational shift operator Date: Thu, 30 Nov 2017 01:07:03 +0300 Lines: 42 Approved: news@gmane.org Message-ID: <0a5bfe0d-0bdd-6f87-c49f-a6691963a8ff@gmail.com> References: <69593098-e2cc-487e-bd14-9001b27aa7c1@isocpp.org> <1660240.TqYmd56DvC@tjmaciei-mobl1> <659853f7-4d67-4cbc-4632-1a7cfc532f44@gmail.com> <1971370.BddXmUsGWe@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1511993223 12211 195.159.176.226 (29 Nov 2017 22:07:03 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 29 Nov 2017 22:07:03 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCXY5TXHWYJRBCO77TIAKGQEZCTJIVA@isocpp.org Wed Nov 29 23:06:58 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f72.google.com ([209.85.215.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eKAVO-0002o0-FP for gclcip-std-proposals@m.gmane.org; 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[178.140.150.13]) by smtp.googlemail.com with ESMTPSA id p73sm469501lfp.9.2017.11.29.14.07.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 29 Nov 2017 14:07:03 -0800 (PST) In-Reply-To: Content-Language: ru X-Original-Sender: andrey.semashev@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=a2xXnZl4; spf=pass (google.com: domain of andrey.semashev@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=andrey.semashev@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:35631 Archived-At: On 11/30/17 00:31, Hyman Rosen wrote: > On Wed, Nov 29, 2017 at 3:52 PM, Andrey Semashev=20 > > wrote: >=20 > Totally valid: > =C2=A0 =C2=A0 =C2=A0 =C2=A0 c =3D int(unsigned(a) + unsigned(b))= ; >=20 >=20 > No, you can't do that in portable code. Some implementation may trap > on conversion overflow, >=20 > another may saturate, third may produce bogus results. The fact that > each of the three >=20 > implementations documented their respective behaviors doesn't help > you at all because your code >=20 > doesn't work. >=20 >=20 > This is not exactly right.=C2=A0=C2=A0[conv.integral] says >=20 > /If the destination type is signed, the value is unchanged if it can be= =20 > represented in the destination type;/ > /otherwise, the value is implementation-defined. > / > So this code is not allowed to trap.=C2=A0 It must produce a value. Right. It may produce a trapping value, though. Still, my point remains. --=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. 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