220 30281 article Path: news.gmane.org!.POSTED!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Zero initialization and std::uinitialized_t Date: Thu, 5 Jan 2017 12:45:11 +0200 Lines: 33 Approved: news@gmane.org Message-ID: References: <875f60fe-18ff-a276-c409-ad6c95450597@gmail.com> 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 1483613116 26437 195.159.176.226 (5 Jan 2017 10:45:16 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 5 Jan 2017 10:45:16 +0000 (UTC) To: "ISO C++ Standard - Future Proposals" Original-X-From: std-proposals+bncBC5JHI7A7ALRBOGHXDBQKGQEL7XZ7CA@isocpp.org Thu Jan 05 11:45:12 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pg0-f72.google.com ([74.125.83.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cP5Xg-0005sb-FK for gclcip-std-proposals@m.gmane.org; Thu, 05 Jan 2017 11:45:08 +0100 Original-Received: by mail-pg0-f72.google.com with SMTP id g1sf1435088156pgn.3 for ; Thu, 05 Jan 2017 02:45:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :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=GrF92KB6ml0QB2v6zPChADBgZXAAOH79wJgrAVPXTzY=; b=n0JhmUrP+wlYsf+jR+6pDQDa4YJ9kxNVR7EpzYIZojqos7PKKchHIpdh4yDILo0Jl8 XNkYmyBYNcXfC29Ilx6GxOlOElKHCTJ3P5ANaEWATURGDDwim6/t2ghwTHcSDcF1MH1g 1AdgvAmZr1k/Fru/jYcThtsvgwMZetC/jlfiB7eBa0bD4hbE51A5Y8BS5pGB2RpGYDnm 2tHNlNuHIAaH1AND63rnBRzmA3xtItZ0RH1LgWgoAgaF8wddmbt7WahoXNQ3AMYpQCYr ymnDTybpWsIGZZjgyam9RA3wepXhjxLp9/NSWGFOiC0JcufE7tG0DcUeES1dboZvl1+l BZbA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to: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=GrF92KB6ml0QB2v6zPChADBgZXAAOH79wJgrAVPXTzY=; b=J77SSCQS1QhGSnTQ5InhRTPH2QZ801tpIyWHMOR6QKPTNPNR6KjPvg6kp55L6fWGLQ OP+cdkAnlBfR9RV/li4bCY00Y79u5XQFXWe3c1EH2cJ9DTn3z+geyVW1jiatLeQDOQJ/ Y+Vo7uVksq1IoXIKulhGK5sNVy7iStSQzWrSFXRPPYdiXtr6OwfDoE42KbDgFrwDJttO 8V+fTnGTtASZQ9GmgtM9M4MqR6VzxTrHCy64mXE+Id8aN7dYAPoO2jvxRgA+akGOxgX1 B/pBenz9BlICqSvmxq4+LWWX73XAwI7xUbpP+gbp0b54Slo/FN1S2NzrRCJYYMaCipZ+ cl/ X-Gm-Message-State: AIkVDXKnr2zDmNR5eRIhnDsVb0jm3qgXOq7cKF53BGy0xHZoIuhI5B4aHYk0G+VKuh24Zg== X-Received: by 10.99.124.13 with SMTP id x13mr39707620pgc.97.1483613112535; Thu, 05 Jan 2017 02:45:12 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.6.227 with SMTP id 90ls30470078otx.34.gmail; Thu, 05 Jan 2017 02:45:12 -0800 (PST) X-Received: by 10.157.43.184 with SMTP id u53mr28260676ota.163.1483613112012; Thu, 05 Jan 2017 02:45:12 -0800 (PST) Original-Received: from mail-oi0-x241.google.com (mail-oi0-x241.google.com. [2607:f8b0:4003:c06::241]) by mx.google.com with ESMTPS id u12si21168805oia.40.2017.01.05.02.45.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 05 Jan 2017 02:45:11 -0800 (PST) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4003:c06::241 as permitted sender) client-ip=2607:f8b0:4003:c06::241; Original-Received: by mail-oi0-x241.google.com with SMTP id v84so78156328oie.2 for ; Thu, 05 Jan 2017 02:45:11 -0800 (PST) X-Received: by 10.202.73.208 with SMTP id w199mr2117375oia.77.1483613111728; Thu, 05 Jan 2017 02:45:11 -0800 (PST) Original-Received: by 10.157.6.129 with HTTP; Thu, 5 Jan 2017 02:45:11 -0800 (PST) In-Reply-To: <875f60fe-18ff-a276-c409-ad6c95450597@gmail.com> X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:4003:c06::241 as permitted sender) smtp.mailfrom=ville.voutilainen@gmail.com; dmarc=pass (p=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:30281 Archived-At: On 5 January 2017 at 10:45, Jonathan M=C3=BCller wrote: > On 05.01.2017 09:43, Ville Voutilainen wrote: >> >> This idea has been floated before, and gets flat-out rejected due to >> the breakage it would introduce. >> > > What breakage? Detrimental performance changes in existing valid code. > Isn't it undefined behavior to use an uninitialized variable? Sure, but said existing code doesn't do that. > So changing it to 0 initialization would only make undefined behavior > defined, bot no one should depend on an uninitialized value anyway. It will also write to certain memory locations twice, when existing code writes to them only once. --=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/CAFk2RUYqMw-i3SgVNNDymeQZ-YEmHQeVpX9dd5vw6iJHeHf= YZg%40mail.gmail.com. .