220 34952 <70e6aa0d-f41a-440c-f0ef-4969535d08ed@gmail.com> 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: Idea about "std::pmr::memory_resource" Date: Sun, 15 Oct 2017 21:12:53 +0200 Lines: 67 Approved: news@gmane.org Message-ID: <70e6aa0d-f41a-440c-f0ef-4969535d08ed@gmail.com> References: <0a8293b4-3246-47a5-9881-bc1ca4b91772@isocpp.org> <60cbae8d-2a6d-4d1b-9fdf-5c4c913ee0a0@isocpp.org> <97632d14-327a-4af6-8e55-35e753f9557c@isocpp.org> <18b21c5c-ab0f-51ed-1b00-d0cda5c7c046@gmail.com> <5accfbfb-91b3-489e-9e2d-b82149b5ce8e@isocpp.org> <4aa86771-6ade-02fa-b77e-6f0e33f230ac@gmail.com> 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 1508094783 23445 195.159.176.226 (15 Oct 2017 19:13:03 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 15 Oct 2017 19:13:03 +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+bncBCUMHC4Z6QGBBN7GR3HQKGQE3JI47ZQ@isocpp.org Sun Oct 15 21:12:59 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wm0-f69.google.com ([74.125.82.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e3oLA-0004LQ-Hf for gclcip-std-proposals@m.gmane.org; Sun, 15 Oct 2017 21:12:48 +0200 Original-Received: by mail-wm0-f69.google.com with SMTP id i124sf7727711wmf.1 for ; Sun, 15 Oct 2017 12:12:56 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1508094776; cv=pass; d=google.com; s=arc-20160816; b=AaKDDV0xWri5I2yhR+8SkohZEkXzod1VefPwF9dCv7gLAaA5ENumq9sdhA+ADbcevT hGCPO+N3ZptywtnlUtqP1qYvhUepFmCXjCXWYY6MuEwG35GYsjPkBXjDGwPQvDrm7pDp DIyO9hl2Lgkmd+X/UQmT8w/AvmCpb1H/2L84+APXoQRUhlLQ/tmwkMiLC3UCkaLqmpnV QfGdr4TmMk56CwQABTk2BvN0w+PH/BbZ5b9QirwhgRGs/PoLqHEryoeB67undJLyO+qt FQ2iuGSsN+K7flWlu5ml9OsBeCk6OV3xOx9JVgKF6fGSGlWbbCmDcYMPGxY4ed5nyGe1 dTJQ== 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=iBwRi3diEFlj5P5aB07cxKsZmPKPR8JbzTlgvR1xGOc=; b=IpyadlyRMRLMBjDZ5HlMWzKhfDQsrHmQ7mjBhIKn6sBXWnhVOpmRnx6NnNxhxbsvVG xBDxFP+DIyNhJrVO17EklMSb38SWa4waFDu6EcZ3KxoQOJqDyHtXOD6t9nKt9td3nws8 Rx0SolGgZHEGYOEHShcvG8gcOqyRIjGZ/tpZAXL5QW7EdRvOuhMaMOkXTMA561ew85w8 2hFiQvbjm/hNYyyNDA8TV4K1Zm2Xc624WE02R8NMEUpbc+rLrwK5oRNytTst4kveOo+0 FnKWB9y+aB9iXywA9C+Tgm0mhdfdMbHPr3fyUz1/eGvDp+xEJjZZZZoOeRElWP ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=BpBO+nDz; spf=pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.41 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=iBwRi3diEFlj5P5aB07cxKsZmPKPR8JbzTlgvR1xGOc=; b=U/y1iUn6av54N1Z2nmJpIH2YhVnygzsWYxFxfazU55FMnVEr6aX6c6O3nenRfnZlQ0 40lOnfs93oZpGmByvNIS7gHsxRtWnsNllL3xlgh/FQFfWObL3w6rUw1RMlmIo0VfM3+h JCth1f41M+wjJL8IYgSzuOi4clGFjgJ2P5MRnEgCfB0yVG3qzSy+AiD9P328mm1waQZd m/3JeXlV9zwG/lEqORVAgqsbDUmD6eKs+z7t9lJvMgMRzZDjnpLey9Rd5cuuk8hADRgj YJNVDjE5knjxrvIDDy7gI9+eVzPXH2GC9oXaE7o8mZjrKx3dq+tKEUqNGKFL1MBn0tiA q56 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=iBwRi3diEFlj5P5aB07cxKsZmPKPR8JbzTlgvR1xGOc=; b=F0YiyuEjcvKYMZOJayIxoQ9TJcq7SRhYGTjVvIsFegDRTuS7gGk4H0yFmsPqn3vtil L40zY5oquDcPOj4pxBDaZs51AF/FljDJdAnGjePTIJ92II+T330p9LlJzaiXnzmowarv vFYut04UQJT+YHFSLuEz55snL2fruOakidVlc4BiP7+mHcU6vTesCQQ9+bhSp2SSw+jw 3vFosro33ypr67ec/hGNI1kTQTECmnPuUIc53rJRtaB0jKkoz59EAtv0IQz8uL7OOxBt BDmBb5ejWCzd36dbEMQQqqV2vwN+SsL0bOSATinCqIa X-Gm-Message-State: AMCzsaWH666zzbcpm5qsjkNukBp+K/1/ZARpir87arj5vN0Wg0m7jRWf Y6j9d5FgAKJUuHdKW0IX3eGR2A== X-Google-Smtp-Source: AOwi7QBXrgg5Jb0inuLjfYm9tW22nzD3BuCkjnS51+78v2Z9zpR0LUGYqbwk746tXBmPj9ysSMWSVg== X-Received: by 10.80.182.75 with SMTP id c11mr1880319ede.4.1508094776131; Sun, 15 Oct 2017 12:12:56 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.80.201.70 with SMTP id p6ls5039744edh.3.gmail; Sun, 15 Oct 2017 12:12:54 -0700 (PDT) X-Received: by 10.80.212.208 with SMTP id e16mr10218745edj.263.1508094774809; Sun, 15 Oct 2017 12:12:54 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1508094774; cv=none; d=google.com; s=arc-20160816; b=rISVNvNKxaov5Fy5Umvw/mEmSoi7/v38G9Is8RnHOyo0SeDTbwJ+M1t6TLuSKG2ObM dqUC47OM1MRXK58o0HxZd9T2UfUSA5jB/x+3twCHzTq6nJaKm588f9Y3ln59BXGZrKEr S0XKsOi3+g6fg+Cw+OrVfjR9ScZ9hzO0j7G9GBArQYpyPURIv/vnFWQoQic/unOCw1XG W5NZ/T8yRE8C/MOQ6TI4YHwBzNy4OxzpFrHLSjbQ1UEepitPr369mnKrmRD+Z+uGZOAT 7Z9+RVHNcvnAACocza5qapwDP5Tp49G6+6BCnuXr7E3nF6wZbHX1qeXJCa5C+TJ4kV3O 9o4w== 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=ZYG/xeXDpVIa+jIUwnp6ryucswEEt+S2ttYF+Rg4GZc=; b=omfq7L3+N5pvItPkOvszFaDwpgp0xNJidMUp2slWZpZASpjx02JMjwn3iI9VOH0hOL 28zA1VeeVyu1ipCsPVWWrXv6mcMOonHniSsmudV64+1i2VptwzCIvOPpDfoRBzELdGiG np2lFYMW09lgFNc8swdwQKZQT006CaaPZ6OwiWKh05SbpQlcIwlarshFHhH+kWMi226p BHUjeFIQi3PrF9KEcSXtrjoPDVbmxgoYJ+2WJJCd6AQJbrSG4Aar1sBkbq4Jpf9yayRw dSoby/nIFB3xp8bkiTnsJyvPye3sTgOR8y/Z/dd4YYxzmQBlYJxVD8em9Kq8uRZcFu8V DVmw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=BpBO+nDz; spf=pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.41 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-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id g40sor2470690edb.22.2017.10.15.12.12.54 for (Google Transport Security); Sun, 15 Oct 2017 12:12:54 -0700 (PDT) Received-SPF: pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.80.148.153 with SMTP id s25mr10101822eda.301.1508094774237; Sun, 15 Oct 2017 12:12:54 -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 33sm4599539edt.4.2017.10.15.12.12.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 15 Oct 2017 12:12:53 -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=BpBO+nDz; spf=pass (google.com: domain of jonathanmueller.dev@gmail.com designates 209.85.220.41 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:34952 Archived-At: On 15.10.2017 20:06, Nevin Liber wrote: > On Sun, Oct 15, 2017 at 11:27 AM, Jonathan M=C3=BCller=20 > >=20 > wrote: >=20 > However, for a hypothetical redesign of the standard library I think > this should be considered. > An allocator interface similar to the simple PMRs as opposed to the > complexity mess that is Allocator, but instead of virtual functions > and class hierarchy it is "concept-based" like Allocator and > provides the possibility of using type erasure. >=20 >=20 > How do you implement a type-erased version of Allocator which can call=20 > construct?=C2=A0 Please provide a link to working code. You don't. I'm deliberately saying an allocator similar to PMRs - it=20 doesn't care about any type T, construction/destruction like the=20 Allocator do. >=20 > Unfortunately, allocators have two jobs: =C2=A0(1) allocate & release mem= ory=20 > and (2) construct and destroy objects.=C2=A0 They also have a major drawb= ack=20 > in that they have to be part of the type system (eg, vector> and= =20 > vector> are different types). >=20 > PMRs are about addressing (1) in such a way that using a different=20 > allocation scheme does not require a different type family (eg,=20 > vector> is the type no matter what=20 > allocation scheme is used). I'm aware. >=20 > If you or the OP has a better way to solve this with the above=20 > constraints, present it.=C2=A0 If you have different constraints, well, t= hat=20 > would be a different proposal and it is a disservice to say that PMRs do= =20 > not meet that need because PMRs are not trying to meet that need. All I'm saying is: there are very special cases where the PMRs=20 implementation with virtual functions has unnecessary overhead. So it would be great if there was a concept like PMRs but without the=20 need for virtual functions. Like the OP described: You simply write a class that provides the same=20 interface and can then plug that into a container. Yes, we already have that facility - Allocator - but Allocator also does=20 construction/destruction and is such unnecessary complex for controlling=20 memory allocation. --=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/70e6aa0d-f41a-440c-f0ef-4969535d08ed%40gmail.com= .. .