220 11485 <0c70b26d-9af9-498d-b27f-37cf7afe9655@isocpp.org> article Path: news.gmane.org!not-for-mail From: Matthew Fioravante Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Controversy and debate: Uninitialized variables by default is a bug Date: Tue, 17 Jun 2014 09:07:30 -0700 (PDT) Lines: 171 Approved: news@gmane.org Message-ID: <0c70b26d-9af9-498d-b27f-37cf7afe9655@isocpp.org> References: <60caa4ef-b32d-40fe-97b6-8918fbb2bd51@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_285_17506883.1403021250950" X-Trace: ger.gmane.org 1403021261 13518 80.91.229.3 (17 Jun 2014 16:07:41 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 17 Jun 2014 16:07:41 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDELF54RTIGRBRGPQGOQKGQE2YDLDKQ@isocpp.org Tue Jun 17 18:07:34 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pb0-f72.google.com ([209.85.160.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Wwvv3-0003hz-UW for gclcip-std-proposals@m.gmane.org; Tue, 17 Jun 2014 18:07:34 +0200 Original-Received: by mail-pb0-f72.google.com with SMTP id ma3sf26286427pbc.11 for ; Tue, 17 Jun 2014 09:07:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=/ykRh4wUoK5YTbNk6KCyo10tT3qUBSB0QRHS19oVyWI=; b=vLj0jUluTPab2ed+0v050ghsoTJ4m4raotWuBHYGu7+oEHHu9ZnF+FSyKfQlgtHghV vsGO1RCscuWpDGynJ+0dzYHZL4FpOfxgLP4SkwwnClIbHcTKOxZ7vWjv8LljvRAV/DvB bbm5dMazzKqcfJDg3iEmhLqD061GxgLNpJiOd9kY1G2NjXCuqa4OreIxgGxV4q5l7zp5 hxECWzrCyS4nIRS6ITb8pBuGXydbVI966y4jWjkoMXTSY+9zSTaHrOs8MG0k+fNCbfmY veRxvCuI0Qz8ZLXD9ZEMpU1wA2ueCev8xENrUtOEuG2a6b+x7HSxOwsmaPTOEJ+zAU+W xSEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=/ykRh4wUoK5YTbNk6KCyo10tT3qUBSB0QRHS19oVyWI=; b=lhowHrI4kyOoO28OkgvnUCZs/ZMVzCyK8G3wIs2GON3YJHV6SDilhRL8QUO0nCbyAm uAGH6U5odyTId5WDHtR/5F1wzDH18r46jFkC3OIAMdO8WLyn2wnTvezLoUzienUTyLTa pyTICpg/u03g10TGhBXbi8+mYt8bwQOFYgm3+kpmjD96hEy9ABJ4CFZYDOa+wTFe4jKP KMJCPVaU77jYT7cUlVm+hBfdF6NGLuk6JfNIbIFqYk9MRTkk2JWJbrhauUEJZVHFqASM Z7ToSjXv2LABzemlMsa4PQ1sY7gbytUVWZFl8JKjBTKkl7/c9DYvuJZwYCoH3mRthSz/ ekzg== X-Gm-Message-State: ALoCoQn3LshIjN/jXxHofuCjrXGEqlUObX4/ObZYtJf10gXwm3sCXX39VhBNfGCqLZuiBwE8T9UG X-Received: by 10.67.4.202 with SMTP id cg10mr1004877pad.42.1403021252827; Tue, 17 Jun 2014 09:07:32 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.37.211 with SMTP id r77ls1781097qgr.10.gmail; Tue, 17 Jun 2014 09:07:32 -0700 (PDT) X-Received: by 10.140.48.101 with SMTP id n92mr64693qga.15.1403021252237; Tue, 17 Jun 2014 09:07:32 -0700 (PDT) In-Reply-To: X-Original-Sender: fmatthew5876@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:11485 Archived-At: ------=_Part_285_17506883.1403021250950 Content-Type: text/plain; charset=UTF-8 On Tuesday, June 17, 2014 11:58:11 AM UTC-4, Ville Voutilainen wrote: > > On 17 June 2014 18:49, Matthew Fioravante > wrote: > > This is going to be controversial, but lets get into it. > > > > The fact that `int x;` creates an uninitialized integer instead of a > default > > initialized one is completely wrong. I consider it a major defect in the > > language, a bug in the standard. > > Well, it's not a bug by any definition that the committee uses, since we > know > about it, and it's 100% intentional. > > > Please now, convince if you can why this is a bad idea. Why should we > > > char buf[MEGABYTE]; > Arrays are not an exception. If buf[MEGABYTE] is a global, its already initialized to 0. If its a class member or on the stack, you can say char buf[MEGABYTE] = void; to skip initialization. Otherwise it gets filled with 0s. > buf[HERE] = something; > buf[THERE] = something_else; > > According to what you propose, the mere definition of buf would go > through all of that > megabyte and zero-initialize the chars. > > Or perhaps you meant that arrays are an exception? What about > > struct X { char buf[MEGABYTE]; }; > > X x; > > Is this also an exception to the rule? > Possibilities here: struct X { char buf[MEGABYTE] = void }; //All default constructed objects of type X will have uninitialized buffers X x; //< buf is not initialized //OR struct X { char buf[MEGABYTE]; }; X x = void; //<-This particular x will not initialize its members by default (Same as X x; now) > > How many performance expectations of how much existing code do you think > this > change would break? > We would need to study this to find out. > > The committee's answer to this question has always been "too many, too > much", and > I don't see that changing. > -- --- 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/. ------=_Part_285_17506883.1403021250950 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Tuesday, June 17, 2014 11:58:11 AM UTC-4, Ville= Voutilainen wrote:
On 17 June = 2014 18:49, Matthew Fioravante <fma= tth...@gmail.com> wrote:
> This is going to be controversial, but lets get into it.
>
> The fact that `int x;` creates an uninitialized integer instead of= a default
> initialized one is completely wrong. I consider it a major defect = in the
> language, a bug in the standard.

Well, it's not a bug by any definition that the committee uses, since w= e know
about it, and it's 100% intentional.

> Please now, convince if you can why this is a bad idea. Why should= we


char buf[MEGABYTE];

Arrays are not an exception.

If buf[MEGABY= TE] is a global, its already initialized to 0.

If its a class member= or on the stack, you can say

char buf[MEGABYTE] =3D void;

t= o skip initialization. Otherwise it gets filled with 0s.


buf[HERE] =3D something;
buf[THERE] =3D something_else;

According to what you propose, the mere definition of buf would go
through all of that
megabyte and zero-initialize the chars.

Or perhaps you meant that arrays are an exception? What about

struct X { char buf[MEGABYTE]; };

X x;

Is this also an exception to the rule?

Possibilities here:

struct X { char buf[ME= GABYTE] =3D void }; //All default constructed objects of type X will have u= ninitialized buffers
X x; //< buf is not initialized

//OR
s= truct X { char buf[MEGABYTE]; };
X x =3D void; //<-This particular x = will not initialize its members by default (Same as X x; now)
 
=

How many performance expectations of how much existing code do you thin= k this
change would break?

We would need to study this to find out.

The committee's answer to this question has always been "too many, too
much", and
I don't see that changing.

--

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