220 31855 article Path: news.gmane.org!.POSTED!not-for-mail From: Alberto Barbati Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: This variable should not be named: an identifier (not) to remember Date: Tue, 28 Mar 2017 22:27:25 +0200 Lines: 104 Approved: news@gmane.org Message-ID: References: <985b9b2a-c734-45eb-95f4-db4dc0d309a1@isocpp.org> <3421677.yAxhhm3ryH@tjmaciei-mobl1> <2009881.g1rS942AcB@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 (1.0) Content-Type: multipart/alternative; boundary=Apple-Mail-2CB7CB11-9E5B-403F-9DB0-F22FDC2D99D2 Content-Transfer-Encoding: 7bit X-Trace: blaine.gmane.org 1490732858 20258 195.159.176.226 (28 Mar 2017 20:27:38 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 28 Mar 2017 20:27:38 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCPY5DV6RIMBBMEO5PDAKGQEDYFBHZA@isocpp.org Tue Mar 28 22:27:33 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f69.google.com ([209.85.215.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1csxi7-0003n7-RF for gclcip-std-proposals@m.gmane.org; Tue, 28 Mar 2017 22:27:23 +0200 Original-Received: by mail-lf0-f69.google.com with SMTP id h125sf38693789lfe.1 for ; Tue, 28 Mar 2017 13:27:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=from:content-transfer-encoding:mime-version:date:subject:message-id :references:in-reply-to: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=p4IEg00pIyi/w7tjE5g0+U+HOBHILGgUOzzI+9txPWQ=; b=phaBRnVIDOIqiVywgKQRKnSn7fJSgxbkQfcurPLOkqw0Hw6A+NLAC81KN8vaEs1z65 U75UozMsaUhk7QC8Jw2ajJr5EVBgxvsxtX76v+KsF9fYruG0WeSWQY9bBIg70DCoVGoK LHgp257pDwfqlAGHrgEnPDD8im51q8MfBvwzDfr8u06sx9z4mA/Xi9Sx+fz4ZHOqi3Ic svhxzAHyFqb48eIxWizlpQKI2xeKxTAdtvcm/iLpYhBjq3BWqV5VKkiL06Xhpu//vD8E efTI+3iljeronYY5MXOdz7yMsHsVA8bWCi2Qyp8ZwjTfeRUQhiYiD+UI8BO6NiV0AGqq xnQw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:content-transfer-encoding:mime-version:date :subject:message-id:references:in-reply-to: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=p4IEg00pIyi/w7tjE5g0+U+HOBHILGgUOzzI+9txPWQ=; b=THPjW+UVbB8057+v30xA7DfBFERy2/RYHmn54fxgxeAk0Hfno2ZMx0UuH/4NORoEQw CpDad9OZM3dCx4BTo5npDx7VydUHyqXLazSKvUUXZRFLYxUYLz6oN3vmBknyvm9k+ZfH 5rtyMlabjtvTjhRST7PbfYjIjsmCUnIPuZPsNb0+fvjGl5scgIUAGkM8rUvfjFhqjSvo KzvqgN0/jemr/G5fhIzGdrGKC97McPjXsgLLMjNX73fEzJsvzHVzoH77R35/rVt90svf bGDyG2QLsyiz1MzX56cyVjOzubi9ETkRSQgg2bP7lb0dFOWD5q1DTZYBRfYQ3+JcvgSL NFz X-Gm-Message-State: AFeK/H3SlpItgorJwlmAII7F0Co2oAuwfRYpxtrW6wErwMVlLuzCRrHbdLVsfjt4fdi1uA== X-Received: by 10.46.1.12 with SMTP id 12mr777673ljb.30.1490732849893; Tue, 28 Mar 2017 13:27:29 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.29.6 with SMTP id d6ls2031117wmd.25.canary-gmail; Tue, 28 Mar 2017 13:27:27 -0700 (PDT) X-Received: by 10.223.162.198 with SMTP id t6mr28996214wra.155.1490732847741; Tue, 28 Mar 2017 13:27:27 -0700 (PDT) Original-Received: from mail-wr0-x22a.google.com (mail-wr0-x22a.google.com. [2a00:1450:400c:c0c::22a]) by mx.google.com with ESMTPS id g16si4541109wmg.45.2017.03.28.13.27.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 Mar 2017 13:27:27 -0700 (PDT) Received-SPF: pass (google.com: domain of albertobarbati@gmail.com designates 2a00:1450:400c:c0c::22a as permitted sender) client-ip=2a00:1450:400c:c0c::22a; Original-Received: by mail-wr0-x22a.google.com with SMTP id w11so95846572wrc.3 for ; Tue, 28 Mar 2017 13:27:27 -0700 (PDT) X-Received: by 10.223.151.69 with SMTP id r63mr27114030wrb.6.1490732847239; Tue, 28 Mar 2017 13:27:27 -0700 (PDT) Original-Received: from [192.168.178.44] ([151.20.212.10]) by smtp.gmail.com with ESMTPSA id k128sm4967687wmf.16.2017.03.28.13.27.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 Mar 2017 13:27:26 -0700 (PDT) In-Reply-To: <2009881.g1rS942AcB@tjmaciei-mobl1> X-Mailer: iPad Mail (14D27) X-Original-Sender: AlbertoBarbati@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of albertobarbati@gmail.com designates 2a00:1450:400c:c0c::22a as permitted sender) smtp.mailfrom=albertobarbati@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:31855 Archived-At: --Apple-Mail-2CB7CB11-9E5B-403F-9DB0-F22FDC2D99D2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable > Il giorno 28 mar 2017, alle ore 18:16, Thiago Macieira ha scritto: >=20 >> On ter=C3=A7a-feira, 28 de mar=C3=A7o de 2017 02:09:54 PDT Alberto Barba= ti wrote: >> In this particular instance, V8's programmer could and probably should h= ave >> used a non-reserved name (for example "m_" would have been a better choi= ce >> regardless). Even the choice of _Nullable was ill-conceived, since >> identifiers beginning with an underscore and an uppercase letter are als= o >> reserved. >=20 > The reason for __ is that it looks unintrusive, which allows for code=20 > generation in a way that is easy to read: >=20 > // Fetch the instance type of the receiver into result register. > __ movp(result, FieldOperand(string, HeapObject::kMapOffset)); > __ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOffset)); I don't see it much easier to read than: m_ movp(result, FieldOperand(string, HeapObject::kMapOffset)); m_ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOffset)); especially when the macro m_ expands to some variation of "masm". Just my o= pinion. A. --=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/A84B1DA8-959F-41CF-AAFE-52F7C56D8056%40gmail.com= .. --Apple-Mail-2CB7CB11-9E5B-403F-9DB0-F22FDC2D99D2 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable

Il giorn= o 28 mar 2017, alle ore 18:16, Thiago Macieira <thiago@macieira.org> ha scritto:

On ter=C3=A7a-feira, 28 de mar=C3=A7o de 2017= 02:09:54 PDT Alberto Barbati wrote:
In this particular instance, V8's programmer could and probably should = have
used a non-rese= rved name (for example "m_" would have been a better choice
regardless). Even the choice of _Nu= llable was ill-conceived, since
identifiers beginning with an underscore and an uppercase lette= r are also
reserved.=

The reason for __ is that it= looks unintrusive, which allows for code
generation in a = way that is easy to read:

 // Fetch = the instance type of the receiver into result register.
&n= bsp;__ movp(result, FieldOperand(string, HeapObject::kMapOffset));  __ movzxbl(result, FieldOperand(result, Map::kInstanceTypeOf= fset));

I don't see it much eas= ier to read than:

    m_ movp(result, FieldOperand(string, HeapObject::kM= apOffset));
    m_ movzxbl(result, F= ieldOperand(result, Map::kInstanceTypeOffset));

especially when the macro m_ expand= s to some variation of "masm". Just my opinion.

A.

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