220 35148 article Path: news.gmane.org!.POSTED!not-for-mail From: =?UTF-8?Q?Jonathan_M=c3=bcller?= 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. Date: Mon, 30 Oct 2017 19:36:55 +0100 Lines: 56 Approved: news@gmane.org Message-ID: References: <58eb77f6-2c2d-4ec1-85f8-08dcfe25a23e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1509388623 11486 195.159.176.226 (30 Oct 2017 18:37:03 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 30 Oct 2017 18:37:03 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCUMHC4Z6QGBBSPC3XHQKGQEXW35GNI@isocpp.org Mon Oct 30 19:36:58 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wm0-f71.google.com ([74.125.82.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e9Evb-0001qi-8K for gclcip-std-proposals@m.gmane.org; Mon, 30 Oct 2017 19:36:51 +0100 Original-Received: by mail-wm0-f71.google.com with SMTP id n8sf6570892wmg.4 for ; Mon, 30 Oct 2017 11:36:59 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1509388618; cv=pass; d=google.com; s=arc-20160816; b=CSltehVmx4+35sofGqlkClooylnDx906loRK6foDRgr+ey9Ppkm0gl/Hzo/YXPYfIx V8v+lPYNlgvR6w8eAlISO30Rkh2rI7lM5/FS3vARUxBX40qxW9OcofCqOaY2C81vZLgs 42bLpA1GuuNKBuwx/6Uac7mLPo8qsSkjWVxFDaAi7IK/ZwJJoqd3r0fJjU8HDM/3oKsU v8gJFsCT7OQcaHsL7kx4b+4VEBSNB+zT807FKlrfEywENrmyK//HhoqMeBWJLrnCCiPX M6L/N3XJ74NGOxGbuXoJwmmjjxqeGAyS4Op1eFo31pgAtRGT3pGjBJwVdGb0patx9Mp2 MjHg== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-unsubscribe:list-subscribe:list-archive:list-help:list-post :list-id:mailing-list:precedence:reply-to:content-transfer-encoding :content-language:in-reply-to:mime-version:user-agent:date :message-id:from:references:to:subject:arc-authentication-results :arc-message-signature:dkim-signature:arc-authentication-results; bh=5OqBbc+ORb3rWHANCMkieFDEpdseZe0TMC5jNNMqspg=; b=vUNltF29RC5eLx6HRPMGsD8HaTz97ZisQXoPbmSSWizu5VedU5gBeqUZK2qOhJQ8C0 t/uqX/GHKGFA8UCClDCa3xRqWrs8oEPCunmIw9tBgaoJJyLph68A3rwK5y5ZqjJOAyjD HAONnAae577C7T0Cs/nktBXv044MCQNwJETemplxDrx7YppskeS0jI2Wy80Lp5YplqDt EEeDHelIcuInqU4su5g2joyeMV28WGSIJYYRFUDpaHrp6xU8nd3t/HUJHyiUiYjshId6 uEUr//1sd5kPq2KRcAV7O19k0e8k7TQk4iyVAVRYVOzh2o0HxAjhDDU2FmHra0 ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=vbYq2cC5; spf=pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jonathanmueller.dev@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=5OqBbc+ORb3rWHANCMkieFDEpdseZe0TMC5jNNMqspg=; b=bkyxT1inVrUeA811VMSQvH9pyd3Nu5J/9U5WhDOd4yPqB/8JXcLCy0xT2eBf6rMhq7 ioCF4M23aZW9cSoKOdTERtAkHFVYaIfdJDIogmzZ8rUdWxQ63REYiiBDgQ8E1XB39XR+ shswaOWfi2MP5SmNnhzLbdmXAkZA1GK3e5yyoHDNf0+A2P82yhsVAgzgwin7kJtM4EQs 7iR2y0k/538rUHUwoDh0n9oV5K9HD/elSZkSB5Vhvre/z2qUYpFTdGX+YEn700UH9vAj CfS5F13wlhpB52L28nPtuxVvO5vggkiQvVLEOQRga6T1vfhTOhLvawUi7gmFE6Jze8nn M3D X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=5OqBbc+ORb3rWHANCMkieFDEpdseZe0TMC5jNNMqspg=; b=GLywLgS41LhjpBLZ6XEfDqZqiMLwbXDoZbTLIbf7Hfuba3oN24TtjKn42VqqC+xLFC asSsvAsKh/zY3ehvkNxFQdyuy3TJCsWIwRDgYhwbjX8FtLmtPiN6UQFccvVUcXImjVWR el6w6vU6eYKZQylvxL0adAVw03xKkARrWpmi688b4qD6Vtm45qMMUFQIMKf7oD4AQLEN I1/gNNiwFt4pNHbyyUajwZYdofcEXFERj2Pp0eZCRRBs3QPVJJ+99y+VEiA4VQcoRnBV oRjKxrZKs1ExxJly74KFzy33+gBJaOEgYT/ELgcxZJ/ X-Gm-Message-State: AMCzsaX60c+Yex68tmKflQfD0hrQ9/noVvFQwfIABhU0HlmjIxhNHRKg CR/Cwz0YYHupz5nZtsmS9CcpHw== X-Google-Smtp-Source: ABhQp+Rr3x1DyQt2HlNGZgWNYniDdTCMEf23nMBC2I7NhHtk1in3YMN63/jQmz7Xj2F8GCrMuft95A== X-Received: by 10.80.163.214 with SMTP id t22mr7525401edb.12.1509388618804; Mon, 30 Oct 2017 11:36:58 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.80.240.143 with SMTP id v15ls5861482edl.4.gmail; Mon, 30 Oct 2017 11:36:57 -0700 (PDT) X-Received: by 10.80.242.154 with SMTP id f26mr13466624edm.6.1509388617664; Mon, 30 Oct 2017 11:36:57 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1509388617; cv=none; d=google.com; s=arc-20160816; b=mlvJM/eYcRfU5RX2K4m+NnV2+Ne3k01Dqhi61DEz9Fj/Gd054mhz7DmV7avLCQtStK vt5qw8RSRsIXwVqi+m5yk2c5SuVOHG46p3qjspFIhQfvsfNJww9lr4RXTCerWMsIXQVL cbYQ4Dtf8Iapcbzo7cWD/LOZwHkhOiITurSY0ETbqEiGruoTfHHOMC/xiNMsqFWUO+gN brZmWQrep9C1RhZTo27lWip126Kerl3P7AOi9YTuHZAt/4neFhO446g4Mu5jx+QaxlGZ F2+ZUF21ihaaUW9NBNU7quLgsNP0HykZUxY7srqS0b3TeviUANEUdRtz34fGvsxZczWg //SQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:to:subject :dkim-signature:arc-authentication-results; bh=lphzRdVkwylpEEDZihVeOjpl5bIBFz0Uu1heYjGVWMI=; b=epm9oCZIaEF+94uSr0d7/BEU/94jJDq24D0Rcd+czhMcoqDPHbEnFqIIBM1r5GBX7E ATSqag7ri2uAHXLeKQJl/1og5XGkhlP+QemNWEWYbQ76oTJE8/HzBHhSBuvYsS4Mz19n OV8GOPbW297r+JLXtRwNB08bm4QfotYE3HWeAmhXgz0mdNcrJlXsArDlJ671tZzYLEXF IaR52SB9BKgMeKDhHKikDIHQJhMdfwmasn7BPmdCYoGdSXzycPkb5mZf2pf5fGIs8B0X tfJPrPIRkB+hAL63/TSyOdRp7sI9IlSrSXVA4ISjRBeiDaxOMb+bMwdcWPQm6GG43sS4 iv5A== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=vbYq2cC5; spf=pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jonathanmueller.dev@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com Original-Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id q7sor7200145edh.11.2017.10.30.11.36.57 for (Google Transport Security); Mon, 30 Oct 2017 11:36:57 -0700 (PDT) Received-SPF: pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; X-Received: by 10.80.146.209 with SMTP id l17mr12868589eda.13.1509388617169; Mon, 30 Oct 2017 11:36:57 -0700 (PDT) Original-Received: from [192.168.1.98] (dslb-084-060-195-012.084.060.pools.vodafone-ip.de. [84.60.195.12]) by smtp.gmail.com with ESMTPSA id h56sm17326140ede.15.2017.10.30.11.36.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 30 Oct 2017 11:36:56 -0700 (PDT) In-Reply-To: Content-Language: en-US X-Original-Sender: jonathanmueller.dev@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=vbYq2cC5; spf=pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jonathanmueller.dev@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-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:35148 Archived-At: On 30.10.2017 17:37, Nevin Liber wrote: > On Mon, Oct 30, 2017 at 11:05 AM, > wrote: >=20 > void(?) unique_ptr::emplace(Args &&... args) { *this =3D > make_unique(std::forward(args)...); } > void(?) shared_ptr::emplace(Args &&... args) { *this =3D > make_shared(std::forward(args)...); } >=20 >=20 > Thoughts: >=20 > * 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.=C2=A0 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".=C2=A0 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). >=20 > Note: =C2=A0I'm not saying these are reasons I would vote against such a= =20 > proposal; rather, these are things which need to be discussed in the=20 > proposal. Furthermore: * The smart pointers and optional behave very differently: optional has=20 value semantics, so it makes sense to say "create a new object". I don't think it makes sense to ask the same from unique_ptr. * If we have `emplace()` what about a constructor of the same form? Yes, there's make_XXX but with class template argument deduction we=20 don't really want make_XXX anymore. * If `ptr.emplace(obj)` works, what about `ptr =3D obj`? If you say no to= =20 assignment because it doesn't make sense, why allow emplace? * Why go through all that just to save a `=3D make_unique(blah)`?=20 That's not too much typing. --=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/ebeab15d-5424-034b-7d86-b84b381a1977%40gmail.com= .. .