220 10940 article Path: news.gmane.org!not-for-mail From: "'Jeffrey Yasskin' via ISO C++ Standard - Future Proposals" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Protect Lambda functions against reflection Date: Wed, 28 May 2014 15:27:14 -0700 Lines: 81 Approved: news@gmane.org Message-ID: References: <108c47a2-d952-4f84-a347-923b2ab742ad@isocpp.org> <7ef3d3da-0c1d-443c-88d2-656b91937170@isocpp.org> <68f98b78-8bd4-48e0-9e1d-47cfc0492764@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 X-Trace: ger.gmane.org 1401316063 9894 80.91.229.3 (28 May 2014 22:27:43 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 28 May 2014 22:27:43 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDDM34EO6QDRBV6FTGOAKGQE6BVD5KQ@isocpp.org Thu May 29 00:27:37 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ve0-f199.google.com ([209.85.128.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WpmJs-0004AT-S3 for gclcip-std-proposals@m.gmane.org; Thu, 29 May 2014 00:27:37 +0200 Original-Received: by mail-ve0-f199.google.com with SMTP id oz11sf47302832veb.10 for ; Wed, 28 May 2014 15:27:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=jqnlcDwiorRtxE1RA+q0OpXKJd9SOVQQv/suVowlOQQ=; b=UqIjmmv6Vd2hC+s14h2vN8TZh9RHl7kawEaITcuviZzSCbCjTnLKoaNnytQJ8sEnnk nOY0gHlY8k+XuImvsfK90UGJjEIHlfyVLtEAr0BhdYssPQVbvw9rS+FFcPluoOwjBGvw btHoba6ugm2CLofwRzvjTwiOJAHQcpVzTwOZ8YJ4yizLq5woNebuWXvTZM6SyMuK0IaD x7d+UBptnsTHAR0nI0eSYM3T1ufaGkUf64eTk0TwqWjHOxEtZisHV/WvrNXyH2KtJZtP IIqceWpjYMTvYQG+AQEMKVoA3+dv3idm/onTcFh2xl4+gyWn0Kyvxubl1pn9wVwTN/RZ I/Fw== X-Gm-Message-State: ALoCoQms6cvpUliocBJZe8oQW77zos9ZruCg6wcD56S4UCw7fiX/4ID330XoUUMSrUqLgNSzo+TI X-Received: by 10.58.38.199 with SMTP id i7mr1324633vek.6.1401316055986; Wed, 28 May 2014 15:27:35 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.109.247 with SMTP id l110ls338820qgf.90.gmail; Wed, 28 May 2014 15:27:35 -0700 (PDT) X-Received: by 10.224.114.145 with SMTP id e17mr3914510qaq.53.1401316055323; Wed, 28 May 2014 15:27:35 -0700 (PDT) Original-Received: from mail-qg0-x232.google.com (mail-qg0-x232.google.com [2607:f8b0:400d:c04::232]) by mx.google.com with ESMTPS id 95si23659397qgt.50.2014.05.28.15.27.35 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 28 May 2014 15:27:35 -0700 (PDT) Received-SPF: pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:400d:c04::232 as permitted sender) client-ip=2607:f8b0:400d:c04::232; Original-Received: by mail-qg0-f50.google.com with SMTP id z60so19685810qgd.37 for ; Wed, 28 May 2014 15:27:35 -0700 (PDT) X-Received: by 10.224.163.8 with SMTP id y8mr4288543qax.46.1401316055147; Wed, 28 May 2014 15:27:35 -0700 (PDT) Original-Received: by 10.229.139.79 with HTTP; Wed, 28 May 2014 15:27:14 -0700 (PDT) In-Reply-To: X-Original-Sender: jyasskin@google.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of jyasskin@google.com designates 2607:f8b0:400d:c04::232 as permitted sender) smtp.mail=jyasskin@google.com; dkim=pass header.i=@google.com; dmarc=pass (p=REJECT dis=NONE) header.from=google.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: , X-Original-From: Jeffrey Yasskin Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:10940 Archived-At: On Wed, May 28, 2014 at 2:48 PM, Diggory Blake wrote: > > > On Wednesday, 28 May 2014 22:18:24 UTC+1, Nevin ":-)" Liber wrote: >> >> On 28 May 2014 15:38, Diggory Blake wrote: >>> >>> Also, access modifiers are not there for security reasons - it's trivial >>> to bypass them if one really wanted to >> >> >> While there are a few places in the language where encapsulation is broken >> (templated member functions, for instance), I don't think it is trivial to >> bypass them in a standard conforming C++ program. Could you give us some >> simple examples? > > > struct Foo { > public: > int m_public; > private: > int m_private; > }; > > struct Bar { > public: > int m_public; > int m_private; > }; > > void setPrivate(Foo* foo, int v) { > ((Bar*)foo)->m_private = v; > } > > C++ allows direct memory access, of course it's trivial to bypass any kind > of access control not enforced by the underlying operating system. This violates basic.lval's aliasing restrictions, which causes undefined behavior. It also relies on the compiler not taking advantage of the permission to reorder things at access control boundaries. That's why Nevin specified "standard conforming". It's true that malicious code within a single process can, in practice, use undefined behavior to get whatever behavior it wants, but undefined behavior still affects who's blamed for breakage. >>> Since reflection is a tool used by the program, not the programmer, >> >> >> Huh? > > > The purpose of reflection is not to do this (pseudocode): > findClass("Foo").construct("Hello, world!") > > Instead of just: > new Foo("Hello, world!") > > If the programmer was the one supplying these arguments then it would be > pointless. If Foo's constructor is private, but reflection allows access to it anyway, people will use reflection to get access to it, and the people trying to maintain Foo will curse us the next time they try to upgrade it. You saying that's not the purpose won't stop any of that from happening. That said, I think I do prefer reflection to ignore access control, and not to provide an escape hatch for class authors. If class authors can't explicitly block reflection, it'll be a bit easier for them to place the blame on the "nitwits" where it belongs. :) Jeffrey -- --- 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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. .