220 35138 article Path: news.gmane.org!.POSTED!not-for-mail From: Nevin Liber Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Add .emplace() method to std::unique_ptr and std::shared_ptr like it is in std::optional. 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[209.85.220.41]) by mx.google.com with SMTPS id l10sor6125412uab.289.2017.10.30.09.38.34 for (Google Transport Security); Mon, 30 Oct 2017 09:38:34 -0700 (PDT) Received-SPF: pass (google.com: domain of nliber@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.176.13.153 with SMTP id i25mr1634534uak.139.1509381514253; Mon, 30 Oct 2017 09:38:34 -0700 (PDT) Original-Sender: nliber@gmail.com Original-Received: by 10.103.71.140 with HTTP; Mon, 30 Oct 2017 09:37:53 -0700 (PDT) In-Reply-To: X-Original-Sender: nevin@eviloverlord.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Fp5FasXD; spf=pass (google.com: domain of nliber@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=nliber@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:35138 Archived-At: --089e082577e0fcdee3055cc6447c Content-Type: text/plain; charset="UTF-8" On Mon, Oct 30, 2017 at 11:05 AM, wrote: > void(?) unique_ptr::emplace(Args &&... args) { *this = >> make_unique(std::forward(args)...); } >> void(?) shared_ptr::emplace(Args &&... args) { *this = >> make_shared(std::forward(args)...); } >> > Thoughts: - Neither shared_ptr nor unique_ptr store an allocator, so shared_ptr::emplace and unique_ptr::emplace are being tied to a particular allocation scheme. This makes it harder when people refactor code to use other allocation schemes. - unique_ptr has a deleter, which may not go along with emplace calling "new". Will this function still exist if default_delete isn't being used? - Unless you templatize it, emplace will not work for polymorphic types, which IMO is one of the major use cases for unique_ptr (and a less major one for shared_ptr). Note: I'm not saying these are reasons I would vote against such a proposal; rather, these are things which need to be discussed in the proposal. -- Nevin ":-)" Liber +1-847-691-1404 -- 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/CAGg_6%2BMhHrsgMcAsqr_BiQu584PzypU%2BGMaRsPuo8XQ7V4RdoA%40mail.gmail.com. --089e082577e0fcdee3055cc6447c Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Mon, Oct 30, 2017 at 11:05 AM, <<= a href=3D"mailto:antanubis@gmail.com" target=3D"_blank">antanubis@gmail.com= > wrote:
void(?) unique_ptr= <T>::emplace(Args &&... args) { *this =3D make_unique<T>= ;(std::forward<Args>(args)...); }
void(?) shared_ptr&l= t;T>::emplace(Args &&... args) { *this =3D make_shared<T>(= std::forward<Args>(args)...); }
<= /div>

Thoughts:
  • Neither s= hared_ptr nor unique_ptr store an allocator, so shared_ptr::emplace and uni= que_ptr::emplace are being tied to a particular allocation scheme.=C2=A0 Th= is makes it harder when people refactor code to use other allocation scheme= s.
  • unique_ptr has a deleter, which may not go along with emplace ca= lling "new".=C2=A0 Will this function still exist if default_dele= te<T> isn't being used?
  • Unless you templatize it, emp= lace will not work for polymorphic types, which IMO is one of the major use= cases for unique_ptr (and a less major one for shared_ptr).
= Note: =C2=A0I'm not saying these are reasons I would vote against such = a proposal; rather, these are things which need to be discussed in the prop= osal.
--
=C2=A0Nevi= n ":-)" Liber=C2=A0 <mailto:nevin@eviloverlord.com> =C2=A0+1-847-691-1= 404

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