220 29345 <6a3dd40c-c25c-2440-b8b5-922700a4d989@honermann.net> article Path: news.gmane.org!.POSTED!not-for-mail From: Tom Honermann Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: std::byte thoughts Date: Wed, 2 Nov 2016 10:14:32 -0400 Lines: 102 Approved: news@gmane.org Message-ID: <6a3dd40c-c25c-2440-b8b5-922700a4d989@honermann.net> References: <7da80620-e4bd-40eb-a4ec-4f3c2dcb2c98@isocpp.org> <1549171.TC16PSHVVd@tjmaciei-mobl1> <2350841.Z7lUCKSumT@tjmaciei-mobl1> <3e64b220-79ae-4108-ba1c-9785494fc434@isocpp.org> <97ebfc84-c5a3-eaf5-efcb-c1bdf9b507a5@gmail.com> <684B5982-22CB-4357-9A1A-09F4588ADA8A@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------636D9CBDB09B259F174D748E" X-Trace: blaine.gmane.org 1478096094 10421 195.159.176.226 (2 Nov 2016 14:14:54 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 2 Nov 2016 14:14:54 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDBNXSHG6UDBBSXJ47AAKGQEQTWWXKQ@isocpp.org Wed Nov 02 15:14:44 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f70.google.com ([209.85.214.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c1wJE-0000BR-Sf for gclcip-std-proposals@m.gmane.org; Wed, 02 Nov 2016 15:14:33 +0100 Original-Received: by mail-it0-f70.google.com with SMTP id q75sf51495113itc.4 for ; Wed, 02 Nov 2016 07:14:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=RAwVUU29lAhvKZldm1q+aqijuZ2aGQ3+I2PahAg6T4M=; b=jx7kUvh3S1y9ottI2RGqhybJZjKbpJI9FF1INfhROiEiGHqqagg2TaK9h0gREeQTpz mRLVSWLW/LcaxHXymkuCgADdjePHrzBnlkOhN5sr9GY1MdS8FGcp413uKSw1B3rhNsNk ZgJIbbQ3x/JHeYpLt9HZRtUDPkY1lQUpdSU5KNnOarFHqLuwKhw9TNrhtLOQX8yTPUli 1508TEc2HRC6Lvz9Zy0jl90rl650JZ13Rbcrtj8M87IgVQqbT57cbFyV5HM4VG0gzg+I JTqhmOWQ6g1x1VxJ5gil7QhFMecdC5263Bica/3x1ou4aoxHcCjksmZInj5nPUOAd707 v8LQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=RAwVUU29lAhvKZldm1q+aqijuZ2aGQ3+I2PahAg6T4M=; b=PmJW56hZ19Y3S2WI8PYASTup5TLJzXksGy8HeO1bDRookMD13rPWHVEMRQ64fGCqWM q9c6M/xuK8eL72iT7YMTu9HtwXCZNh5bvGSyX/jNziIRENyACl8iwKq4tcoyjDRe/5mt UR4BudCnr5GZdcOEyUM9RSO4N3fIXN0ROxJHEvvkXs5c6ZWtAwvq+s4geukbbHdaldlk x6phRehQI7tC3zhgxOJNJqqGdEW9hsl8vOZiez7OpjOsV+GMBy7rcxnYO/MIJds4INks 37vq+JvF13hY4ThLCDWHaT7GLQYR+AmQOdzrX8QrChz/W1UFMnDN29TSTD7kITW6Ru+S NgXQ== X-Gm-Message-State: ABUngvcfbQmIELQYZKh22pT55X/Y2Eb1X02MW4IMTwUY9VdSNu6b4uzbJ7gCn2GGPI4TRQ== X-Received: by 10.36.98.11 with SMTP id d11mr3161067itc.3.1478096075533; Wed, 02 Nov 2016 07:14:35 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.143.210 with SMTP id r201ls2257142iod.11.gmail; Wed, 02 Nov 2016 07:14:34 -0700 (PDT) X-Received: by 10.107.41.4 with SMTP id p4mr4346952iop.16.1478096073991; Wed, 02 Nov 2016 07:14:33 -0700 (PDT) Original-Received: from smtp123.ord1c.emailsrvr.com (smtp123.ord1c.emailsrvr.com. [108.166.43.123]) by mx.google.com with ESMTPS id z13si21498097itc.86.2016.11.02.07.14.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 02 Nov 2016 07:14:33 -0700 (PDT) Received-SPF: neutral (google.com: 108.166.43.123 is neither permitted nor denied by best guess record for domain of tom@honermann.net) client-ip=108.166.43.123; Original-Received: from smtp8.relay.ord1c.emailsrvr.com (localhost [127.0.0.1]) by smtp8.relay.ord1c.emailsrvr.com (SMTP Server) with ESMTP id 73BC8A05C6 for ; Wed, 2 Nov 2016 10:14:33 -0400 (EDT) X-Auth-ID: tom@honermann.net Original-Received: by smtp8.relay.ord1c.emailsrvr.com (Authenticated sender: tom-AT-honermann.net) with ESMTPSA id 561DAA0565 for ; Wed, 2 Nov 2016 10:14:33 -0400 (EDT) X-Sender-Id: tom@honermann.net Original-Received: from [192.168.1.16] (pool-71-176-249-9.rcmdva.fios.verizon.net [71.176.249.9]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA) by 0.0.0.0:587 (trex/5.7.7); Wed, 02 Nov 2016 10:14:33 -0400 In-Reply-To: <684B5982-22CB-4357-9A1A-09F4588ADA8A@gmail.com> X-Original-Sender: tom@honermann.net X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 108.166.43.123 is neither permitted nor denied by best guess record for domain of tom@honermann.net) smtp.mailfrom=tom@honermann.net 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:29345 Archived-At: This is a multi-part message in MIME format. --------------636D9CBDB09B259F174D748E Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable On 11/02/2016 08:14 AM, Miro Knejp wrote: > I think this is the real issue here: a type that is dedicated to=20 > represent only characters and not allowed to alias anything else.=20 > Having a char* can severely limit the compiler=E2=80=99s ability to optim= ize=20 > your function because of all the aliasing implications, even if you as=20 > the author know it never aliases anything because it actually *is* a=20 > string. Having a type that clearly conveys this semantic to the=20 > compiler would be useful. I recall this being discussed during the presentation of P0257R0=20 in=20 Jacksonville; thoughts were expressed that, if an alternative type to=20 accommodate aliasing needs can be popularized, then perhaps the aliasing=20 behaviors of char can be removed in some future standard. I think that=20 is a more realistic perspective than popularizing a new type to replace=20 char. I'll note that the char8_t type proposed in P0482R0=20 =20 for UTF-8 characters and strings would not include char's aliasing=20 behavior, thus at least allowing for more optimization possibilities for=20 UTF-8 characters/strings. Tom. --=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/6a3dd40c-c25c-2440-b8b5-922700a4d989%40honermann= ..net. --------------636D9CBDB09B259F174D748E Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On 11/02/2016 08:14 AM, Miro Knejp wrote:
I think this is the real issue here: a type that is dedicated to represent only characters and not allowed to alias anything else. Having a char* can severely limit the compiler=E2=80= =99s ability to optimize your function because of all the aliasing implications, even if you as the author know it never aliases anything because it actually *is* a string. Having a type that clearly conveys this semantic to the compiler would be useful.
I recall this being discussed during the presentation of P0257R0 in Jacksonville; thoughts were expressed that, if an alternative type to accommodate aliasing needs can be popularized, then perhaps the aliasing behaviors of char can be removed in some future standard.=C2=A0 I think that is a more realistic perspective than popularizing a new type to replace char.=C2=A0 I'll note that the char8= _t type proposed in P0482R0 for UTF-8 characters and strings would not include char's aliasing behavior, thus at least allowing for more optimization possibilities for UTF-8 characters/strings.

Tom.

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