220 17566 <5c67669c-7812-43a5-a8fd-21dcc6f8894a@isocpp.org> article Path: news.gmane.org!not-for-mail From: lie4pan1 Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Thoughts/idea about N4401 vs N4475 (regarding raw ptrs and mutables) Date: Wed, 29 Apr 2015 02:09:56 -0700 (PDT) Lines: 260 Approved: news@gmane.org Message-ID: <5c67669c-7812-43a5-a8fd-21dcc6f8894a@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_6987_3080161.1430298596744" X-Trace: ger.gmane.org 1430298616 21725 80.91.229.3 (29 Apr 2015 09:10:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 29 Apr 2015 09:10:16 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCEP3ZH7SICRBZN7QKVAKGQEDTL6YOY@isocpp.org Wed Apr 29 11:10:02 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f69.google.com ([209.85.220.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YnO0F-00032E-Mq for gclcip-std-proposals@m.gmane.org; Wed, 29 Apr 2015 11:10:00 +0200 Original-Received: by pabvw2 with SMTP id vw2sf36887316pab.2 for ; Wed, 29 Apr 2015 02:09:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:subject:mime-version:content-type :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=xflQ0oGp7FUSy4WoBNx6QhZrR3lwRKD8bdvqJz77S2c=; b=L3oWp7rH4MkiTRPiUNB2zb9MMoKAnLkcshPuPGVmYNVCDwtZ75N1POvqNgJC5X07MY i2+S4ET9qiiSNpfh4zbLhA6rQZQPY3kCQzc8GAsJiHzFBKalyJAufa4JrkHCikSZrCnM 1PrHsVoGqUfXZ+a3or1wbWCVZwtyZgNL+3FF//hKGaq9vaCKnThk7E+n5uejwM5QYRKH LKNY2/kLSox4BrRImAaqlkY14p4WVpTnTv3KvNdOo8I9XAnlM35LVWsMZYdXog3c9ifp n5LagUMUe89gBmeeHIf5oiG6LCziU7JZvC6/YlV3vIdaf44vkx9b65o5dHiwrAGbrD3R 6I5w== 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:subject:mime-version :content-type:x-original-sender:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=xflQ0oGp7FUSy4WoBNx6QhZrR3lwRKD8bdvqJz77S2c=; b=HWRvT4Nu4OUG/H2Xfhx6c3Il1JzcDRPs4ovQrwGO0VWjuUl2dUFsHneSBRkgkzUyGP SmKERx2Oi/8MxmpGLfsg7lRMadOV2zL6k8dd/dy8hk34Klsz/2mu5qHQjej7nxrauPzy gE4VOtvMIwMTX7pKg7aoYbbECo3d1HojYbxGhVFm9DblWj+OduDaU467hMA4+LnWkzvg cy1ExHB+u+hYpQ532clOb32xUxEjSPNy2l+k6yTZVU2ou43PfgWwrzK95jN8vbg1ZnGn /4B0+ViX6Y8LrbTYS82yxEO//LJdZp3tQQTShAJRj6RjB7aj6W+64uCfxDEO4CYSbkRC dsiQ== X-Gm-Message-State: ALoCoQmWLziGFY5CtfKgY874aL4LOSp/N5XEaBOEkJkoYAC7r9nFxCVhJh99WyRWNRllnuLzDv3V X-Received: by 10.66.101.6 with SMTP id fc6mr34250396pab.36.1430298598520; Wed, 29 Apr 2015 02:09:58 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.99.49 with SMTP id p46ls657356qge.51.gmail; Wed, 29 Apr 2015 02:09:57 -0700 (PDT) X-Received: by 10.140.100.136 with SMTP id s8mr249376qge.2.1430298597612; Wed, 29 Apr 2015 02:09:57 -0700 (PDT) X-Original-Sender: lie4pan1@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:17566 Archived-At: ------=_Part_6987_3080161.1430298596744 Content-Type: multipart/alternative; boundary="----=_Part_6988_228658399.1430298596744" ------=_Part_6988_228658399.1430298596744 Content-Type: text/plain; charset=UTF-8 Hi! I've read about some proposals papers on defaulted comparison operators. I like the idea that some comparisons (see below) be default-generated, but I don't think *inconsistent* 'default-generated operators' rules that could only resolve part of the problem regarding raw pointers and mutables are good for a language like C++ that is already so complicated. Difference should look different. How about: class MyClass { // Existence of '__cookie__' non-mutable raw pointers prevent the compiler from generating defaulted copy-ctor, operator== etc. // However, if there were no such pointers (in this example, __cookie__ Datum *newed_), // the default-generated copy-ctor should only (shallow-)copy non-'__cookie__' members ignoring '__cookie__' ones, // the default-generated operator== shall only (shallow-)compare non-'__cookie__' members ignoring '__cookie__' ones, // and so on. private: const Object *one_; // non-owning observer pointer, can be treated trivially private: __cookie__ Datum *newed_; // non-mutable owning pointer, shouldn't be shallow-copied/compared, thus suppressing defaulted __cookie__ mutable Cache_ last_; // some cache data, should be ignored in comparisons, in common sense __cookie__ mutable bool dirty_; // some cache invalidation flag, same treatment as above private /*friend class IntrsiveList*/: // <- please ignore this block comment :-p __cookie__ mutable MyClass *next_; // I would argue that this is mutable because it is not part of the object's internal state, // thus it should be ignored for object copying and comparisons }; // Pros: // * New syntax/keyword. // * Clearer expression/documentation of intention on data members of the class author(s). // * Provides a simple way to somehow fix the old-ish defaulted copy-ctor/assignment issues with raw pointer / mutable members. // * Things that should work without extra work eg. raw observer pointers work. // Cons: // * New syntax/keyword. // * Buggy code that fails to add '__cookie__' where necessary might be misused (with the newly defaulted comparison operators). That is basically N4401 + new '__cookie__' rules. The new rules are consistent with all defaulted operators. (Yes I am only talking about defaulted operator== and operator!= here because I am unsure about other comparisons related to ordering.) -- --- 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_6988_228658399.1430298596744 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Hi!

I've read about some pr= oposals papers on defaulted comparison operators. I like the idea that some comparisons (see below) be defaul= t-generated, but I don't think inconsistent 'default-generated oper= ators' rules = that could only resolve part of the problem regarding raw pointers and mutables<= /span> are good for a language like C++ that is already so c= omplicated.

 Difference should look different. How about:

class MyClass
{
// Existence of '__cookie__' non-mutable ra= w pointers prevent the compiler from generating defaulted copy-ctor, operat= or=3D=3D etc.
// = However, if there were no such pointers (in this example, __cookie__ Datum = *newed_),<= br>// the = default-generated copy-ctor should only (shallow-)copy non-'__cookie__' mem= bers ignoring '__cookie__' ones,
// the default-generated operator=3D=3D shall only (shallow-)compa= re non-'__cookie__' members ignoring '__cookie__' ones,
// and so on.
private:
    const Object *on= e_;=     &n= bsp;          // non-owning observer pointer, can be treated= trivially=
privat= e:<= span style=3D"color: #000;" class=3D"styled-by-prettify">
    = __cookie__ Datum *newed_;          = // non-mut= able owning pointer, shouldn't be shallow-copied/compared, thus suppressing= defaulted=
    __cookie__ mutable Cache_ last_;=   // some cach= e data, should be ignored in comparisons, in common sense
    __cookie__= mutable bool dirty_;    // some cache invalidation flag, = same treatment as above
private /*fri= end class IntrsiveList*/: // &= lt;- please ignore this block comment :-p
    __cookie__ mutable MyClass *next_; // I w= ould argue that this is mutable because it is not part of the object's inte= rnal state,
                    =                    // thus it shoul= d be ignored for object copying and comparisons
};

// Pros:
// * New syntax/keyword.
// * Clearer expression/documentation of intentio= n on data members of the class author(s).
// * Provides a simple way to somehow fix the old-= ish defaulted copy-ctor/assignment issues with raw pointer / mutable member= s.
// * Things th= at should work without extra work eg. raw observer pointers work.
// Cons:
// * New syntax/keyword.
// * Buggy code that fails= to add '__cookie__' where necessary might be misused (with the newly defau= lted comparison operators).


That is basically N4401 + new '__cookie__' rules= .. The new rules are consistent with all defaulted operators.
(Yes I am only talking a= bout defaulte= d operator=3D=3D and operator!=3D here because I am unsure ab= out other comparisons<= span style=3D"font-family: arial,sans-serif;"> rela= ted to ordering.)

--

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