220 36548 article Path: news.gmane.org!.POSTED!not-for-mail From: Richard Hodges Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: What happened to N4282 Date: Sun, 7 Jan 2018 23:38:54 +0100 Lines: 193 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a113f3446bb60a5056237586f" X-Trace: blaine.gmane.org 1515364618 16151 195.159.176.226 (7 Jan 2018 22:36:58 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 7 Jan 2018 22:36:58 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD4PBM7UWAHRB76CZLJAKGQEFVDQ37A@isocpp.org Sun Jan 07 23:36:53 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-io0-f197.google.com ([209.85.223.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eYJYj-0003sJ-AB for gclcip-std-proposals@m.gmane.org; Sun, 07 Jan 2018 23:36:53 +0100 Original-Received: by mail-io0-f197.google.com with SMTP id q16sf3674970ioh.4 for ; 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[209.85.220.41]) by mx.google.com with SMTPS id d133sor5646910iof.177.2018.01.07.14.38.55 for (Google Transport Security); Sun, 07 Jan 2018 14:38:55 -0800 (PST) Received-SPF: pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.107.7.227 with SMTP id g96mr9559254ioi.201.1515364734949; Sun, 07 Jan 2018 14:38:54 -0800 (PST) Original-Received: by 10.2.181.55 with HTTP; Sun, 7 Jan 2018 14:38:54 -0800 (PST) In-Reply-To: X-Original-Sender: hodges.r@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=ZvdDrtmb; spf=pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hodges.r@gmail.com; dmarc=pass (p=NONE sp=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-Spam-Checked-In-Group: std-proposals@isocpp.org 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:36548 Archived-At: --001a113f3446bb60a5056237586f Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable I wrote my own observer_ptr too, feeling that it states intent explicitly. However, it's probably true that std::reference_wrapper<> does the same job. It's just a little less convenient when talking to c apis. I don't like seeing naked pointers in c++ code. I'd be inclined to reject code that used them at code review time unless it could be proven they were necessary. On 7 January 2018 at 23:17, Bo Persson wrote: > On 2018-01-07 18:07, Masse Nicolas wrote: > >> Hi all, >> >> Le dimanche 10 d=C3=A9cembre 2017 23:07:54 UTC+1, Nicol Bolas a =C3=A9cr= it : >> >> >> Basically, naked pointers are treated like a hypothetical >> `optional`. If you want an owning pointer, you use a smart >> pointer or, if you cannot properly encapsulate the ownership, >> `gsl::owner`. If you want a non-owning array, you use >> `gsl::span`. >> >> People are going to use `T*` for non-owning pointers; there's no >> getting around that. We already have one way to spell that; we don't >> need a second one. >> >> >> I should say I just don't agree with you. >> When people use naked pointer, we can't know wether it is: >> - for storing a non-owned pointer >> - due to compatibility with C code >> - poorly written code >> - whathever >> >> Also it goes against a rule I've set with myself who said that naked >> pointer should always be avoided :D. >> >> On the other side, when using std::observer_ptr, you know: >> - that the given pointer isn't owned and that you should not try to take >> any ownership on it. >> - the code is not that poorly written :) >> >> > The trend for the C++ Core Guidelines seems to be that a raw pointer is > non-owning (and non-array). > > http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rr-ptr > > And then use the compilers' static analysis to warn about doing "owning > things" to the pointers. > > I think the observer_ptr, while a good idea in isolation, has lost to the > more comprehensive guidelines. > > > Bo Persson > > > -- > 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. > To view this discussion on the web visit https://groups.google.com/a/is > ocpp.org/d/msgid/std-proposals/p2u66r%245uh%241%40blaine.gmane.org. > --=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/CALvx3hY-kSJAN5jbpp0gSK0GWBtEPpK%3DJx5XR3DsUxJLq= Ag%2BbA%40mail.gmail.com. --001a113f3446bb60a5056237586f Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I wrote my own observer_ptr too, feeling that it states in= tent explicitly.

However, it's probably true that st= d::reference_wrapper<> does the same job. It's just a little less= convenient when talking to c apis.

I don't li= ke seeing naked pointers in c++ code. I'd be inclined to reject code th= at used them at code review time unless it could be proven they were necess= ary.


On 7 January 2018 at 23:17, Bo Persson <bop@gmb.dk> wrote:
On = 2018-01-07 18:07, Masse Nicolas wrote:
Hi all,

Le dimanche 10 d=C3=A9cembre 2017 23:07:54 UTC+1, Nicol Bolas a =C3=A9crit= =C2=A0:


=C2=A0 =C2=A0 Basically, naked pointers are treated like a hypothetical
=C2=A0 =C2=A0 `optional<T&>`. If you want an owning pointer, you = use a smart
=C2=A0 =C2=A0 pointer or, if you cannot properly encapsulate the ownership,=
=C2=A0 =C2=A0 `gsl::owner<T>`. If you want a non-owning array, you us= e `gsl::span<T>`.

=C2=A0 =C2=A0 People are going to use `T*` for non-owning pointers; there&#= 39;s no
=C2=A0 =C2=A0 getting around that. We already have one way to spell that; w= e don't
=C2=A0 =C2=A0 need a second one.


I should say I just don't agree with you.
When people use naked pointer, we can't know wether it is:
- for storing a non-owned pointer
- due to compatibility with C code
- poorly written code
- whathever

Also it goes against a rule I've set with myself who said that naked po= inter should always be avoided :D.

On the other side, when using std::observer_ptr<T>, you know:
- that the given pointer isn't owned and that you should not try to tak= e any ownership on it.
- the code is not that poorly written :)


 The trend for the C++ Core Guidelines seems to be that a raw pointer is non= -owning (and non-array).

http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rr-ptr

And then use the compilers' static analysis to warn about doing "o= wning things" to the pointers.

I think the observer_ptr, while a good idea in isolation, has lost to the m= ore comprehensive guidelines.


=C2=A0 =C2=A0 Bo Persson


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 To view this discussion on the web visit https://groups.google.com/a/isocp= p.org/d/msgid/std-proposals/p2u66r%245uh%241%40blaine.gmane.org.

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