220 31586 <1607497.4jKLvpMD02@tjmaciei-mobl1> article Path: news.gmane.org!.POSTED!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: First draft of [[unreachable]] attribute proposal Date: Mon, 13 Mar 2017 16:23:52 -0700 Lines: 44 Approved: news@gmane.org Message-ID: <1607497.4jKLvpMD02@tjmaciei-mobl1> References: <996e889d-5922-4e13-84dd-d914ec44f5a4@isocpp.org> <51fa0491-97aa-48c8-b361-353f5ecc7a0f@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1489447439 9997 195.159.176.226 (13 Mar 2017 23:23:59 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 13 Mar 2017 23:23:59 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCB4TK757YBRBDGUTTDAKGQE2LDVUTA@isocpp.org Tue Mar 14 00:23:53 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f69.google.com ([74.125.83.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cnZJh-0001x2-2H for gclcip-std-proposals@m.gmane.org; Tue, 14 Mar 2017 00:23:53 +0100 Original-Received: by mail-pg0-f69.google.com with SMTP id 77sf318156170pgc.5 for ; Mon, 13 Mar 2017 16:23:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding: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=gj90rIG54w5I30obiwJk93zQBlS2C1ir78/O+gU5P2c=; b=LrGL8ZKh+439Of54Tqq6OnZsE5DHdTFYucb8ofSDSUY09a9HDBwJY8xsn8JoUBMq/1 ToJ88klFpdQe3FDlORazFxaaQl/OEzSYnfBheQqocby77eQ+tIITXXs2yadxItbU0Ccd LxEZaLmEcShdCrxE/vEvIOELVgT73rGLY61/UXlEdUAzwSHFVO8VwKGT88nNkKDopa6z 6Lr/2GcIfBnL6PZyByyFQCwFms7d3w5nHXsIuZNIOL3HDzAs0Ud2+KbfPX6kAF0F7rvM /IJMjzr/p94Ch0m7uqzMtPSdHt6ohh3zU5YW+pPEH6Lz5gLrg1Y+LZrP+EWaniemmP6H 6mxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding: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=gj90rIG54w5I30obiwJk93zQBlS2C1ir78/O+gU5P2c=; b=Z0lyRWOjIJAXpHsAW93YUtc9lujxVNkwHUuPdrhHl5XV1NIlSHtZnESeN8u2ttClJL QDFqD58RhvDbLs2R8CHJJV8mQSKax8OeMQbvIE98iEdQN+ZcM2q15ZCsDXHoFYtWeWE6 Tr/hhyJqGPcJ71YCG/tdySeM08BhMZOSBEobFQsE2sHO37bcBYzRp/568hIAiutqFtRR ZD8stUV/bJRLcPS3ZpL1KZqRwNOhwP8+xu1ewKYB3jv2NMXp9xJfwFk2clpllTeCVX+W wa+2MSAW0oZWTYhoUldYfFl82u0W8K1w7lzRnNsWJRxccSPxGvjW9SXi7T8uU+0myF+3 kvJ X-Gm-Message-State: AMke39l2Ba1eEXKC4hr5LiVgY3CUey6QSr8f9rAH0AkyBmqvzXeI9yJ0ly38Bh1fMq7KoA== X-Received: by 10.99.109.10 with SMTP id i10mr17380602pgc.152.1489447437312; Mon, 13 Mar 2017 16:23:57 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.4.119 with SMTP id 110ls14618306otc.44.gmail; Mon, 13 Mar 2017 16:23:56 -0700 (PDT) X-Received: by 10.55.214.209 with SMTP id p78mr33242521qkl.255.1489447436439; Mon, 13 Mar 2017 16:23:56 -0700 (PDT) Original-Received: from gondolin.macieira.info (gondolin.macieira.info. [78.47.120.188]) by mx.google.com with ESMTP id w3si1639266qtg.225.2017.03.13.16.23.56 for ; Mon, 13 Mar 2017 16:23:56 -0700 (PDT) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) client-ip=78.47.120.188; Original-Received: from tjmaciei-mobl1.localnet (jfdmzpr02-ext.jf.intel.com [134.134.137.71]) by gondolin.macieira.info (Postfix) with ESMTPSA id 30D3E11B533 for ; Mon, 13 Mar 2017 16:23:54 -0700 (PDT) In-Reply-To: <51fa0491-97aa-48c8-b361-353f5ecc7a0f@isocpp.org> X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 78.47.120.188 as permitted sender) smtp.mailfrom=thiago@macieira.org 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:31586 Archived-At: Em segunda-feira, 13 de mar=C3=A7o de 2017, =C3=A0s 13:28:28 PDT, Myriachan= escreveu: > I noticed that the draft of contractual programming does not say that > behavior is undefined if the expression is false past an [[assert axiom]]= .. > I asked co-author Professor J. Daniel Garcia about why the Standardese > didn't say that the behavior is undefined, and his reply was: >=20 > > Because that is not necessarily true. It is just that the assertion is = not > > checked. I'm not sure I understand the answer. Let's say I have this in my code: [[assert: q.is_valid()]]; According to the answer, the assertion is something that the compiler need = not=20 check anymore in the future, because I asserted that it is true. So what if= I=20 have later in the code path (possibly in an inlined function) if (q.is_valid()) return q.pop(); How will the compiler react? If it deletes the check because I asserted its= =20 result, it will call q.pop(), which may lead to a crash. Isn't that the definition of UB? --=20 Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center --=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/1607497.4jKLvpMD02%40tjmaciei-mobl1. .