220 28951 <986ffd0c-7466-476a-96af-525aaf8b24ea@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Is World's Dumbest Pointer still on the table?!? Date: Tue, 18 Oct 2016 13:09:48 -0700 (PDT) Lines: 141 Approved: news@gmane.org Message-ID: <986ffd0c-7466-476a-96af-525aaf8b24ea@isocpp.org> References: <8a6731f7-1c9b-482d-817e-c2374fc9ae1b@isocpp.org> <7d817482-e7c3-4724-9501-738d4c9083d7@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1563_1074292619.1476821388357" X-Trace: blaine.gmane.org 1476821416 9944 195.159.176.226 (18 Oct 2016 20:10:16 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 18 Oct 2016 20:10:16 +0000 (UTC) Cc: mihailnajdenov@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBDUDTLAAKGQEXCBFWKI@isocpp.org Tue Oct 18 22:10:12 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f200.google.com ([209.85.161.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bwahq-000840-6L for gclcip-std-proposals@m.gmane.org; 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Tue, 18 Oct 2016 13:09:52 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.6.67 with SMTP id 64ls229789iog.53.gmail; Tue, 18 Oct 2016 13:09:50 -0700 (PDT) X-Received: by 10.36.65.22 with SMTP id x22mr403666ita.1.1476821390067; Tue, 18 Oct 2016 13:09:50 -0700 (PDT) In-Reply-To: X-Original-Sender: jmckesson@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:28951 Archived-At: ------=_Part_1563_1074292619.1476821388357 Content-Type: multipart/alternative; boundary="----=_Part_1564_2015910521.1476821388357" ------=_Part_1564_2015910521.1476821388357 Content-Type: text/plain; charset=UTF-8 On Tuesday, October 18, 2016 at 9:44:40 AM UTC-4, mihailn...@gmail.com wrote: > > On Tuesday, October 18, 2016 at 4:17:29 PM UTC+3, Ville Voutilainen wrote: >> >> On 18 October 2016 at 16:08, wrote: >> > In any case, for a smart pointer, reset and release are lifetime >> management >> > interfaces. >> > >> > observer_ptr changes this. >> >> But yet its users are unlikely to find this a problem, because some of >> them don't consider >> reset and release to be lifetime management interfaces. >> > > reset and release is lifetime interface in the context of a smart pointer > - if you touch these, the lifetime of the object will change. > That's a fact, not a point a view. > No, it is a point of view. To hold onto a smart pointer object means that you expect the object pointed to by the smart pointer to continue to exist, pursuant to the smart pointer's contract. A `weak_ptr` does not ensure the lifetime of the pointed-to object. What it does ensure is that, if that lifetime has ended, you'll know about it. You may get a NULL pointer, but you'll never get an invalid one. When you `reset` a smart pointer, you are saying that you no longer expect that object to exist. Whether or not it is actually destoryed is smart-pointer specific. `shared_ptr::reset` doesn't guarantee the object will be destroyed. `weak_ptr::reset` doesn't destroy anything at all. By calling `reset`, you are making a contract with the smart pointer. From that point forward, you will not do anything to access the object referenced by that smart pointer, nor any object who's lifetime depends on it, *unless* you have a guarantee from some other object. That is, as far as this particular smart pointer is concerned, it is not going to ensure anything. `release` isn't even a function that most smart pointers have. observer_ptr pretends to be smart with risk of being harmful and/or > confusing. > To whom is it harmful or confusing? Are you actually trying to claim that someone is going to assume that a smart pointer with the word "observer" in it is going to manage memory? Anyone who does that *deserves* what they get. The point of `observer_ptr` is to represent when a function is being given a pointer it does not have ownership of. -- 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/isocpp.org/d/msgid/std-proposals/986ffd0c-7466-476a-96af-525aaf8b24ea%40isocpp.org. ------=_Part_1564_2015910521.1476821388357 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Tuesday, October 18, 2016 at 9:44:40 AM UTC-4, mihailn.= ...@gmail.com wrote:
On Tuesday, October 18, 2016 at 4:17:29 PM UTC+3, Ville Voutilainen w= rote:
On 18 October 2016 at 16:08, = =C2=A0<mihailn...@gmail.com> wrote:
> In any case, for a smart pointer, reset and release are lifetime m= anagement
> interfaces.
>
> observer_ptr changes this.

But yet its users are unlikely to find this a problem, because some of
them don't consider
reset and release to be lifetime management interfaces.

reset and release is lifetime interfac= e in the context of a smart pointer -=C2=A0 if you touch these, the lifetim= e of the object will change.
That's a fact,=C2=A0not a point= a view.

No, it is a point of view.
To hold onto a smart pointer object means that you expect the object point= ed to by the smart pointer to continue to exist, pursuant to the smart poin= ter's contract. A `weak_ptr` does not ensure the lifetime of the pointe= d-to object. What it does ensure is that, if that lifetime has ended, you&#= 39;ll know about it. You may get a NULL pointer, but you'll never get a= n invalid one.

When you `reset` a smart pointer, you are saying that= you no longer expect that object to exist. Whether or not it is actually d= estoryed is smart-pointer specific. `shared_ptr::reset` doesn't guarant= ee the object will be destroyed. `weak_ptr::reset` doesn't destroy anyt= hing at all.

By calling `reset`, you are making a contract with the = smart pointer. From that point forward, you will not do anything to access = the object referenced by that smart pointer, nor any object who's lifet= ime depends on it, unless you have a guarantee from some other objec= t. That is, as far as this particular smart pointer is concerned, it is not= going to ensure anything.

`release` isn't even a function that = most smart pointers have.

observer_ptr pretends to be smart= with risk of being harmful and/or confusing.

To whom is it harmful or confusing? Are you actually tryin= g to claim that someone is going to assume that a smart pointer with the wo= rd "observer" in it is going to manage memory?

Anyone who = does that deserves what they get.

The point of `observer_ptr`= is to represent when a function is being given a pointer it does not have = ownership of.

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/986ffd0c-7466-476a-96af-525aaf8b24ea= %40isocpp.org.
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