220 19523 article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: try_realloc Date: Sun, 2 Aug 2015 14:29:13 +0800 Lines: 103 Approved: news@gmane.org Message-ID: References: <30f59ec7-0712-48fb-9df0-d66e3fe80c3c@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_DD0B3623-5087-4177-B5D5-58D786462855" X-Trace: ger.gmane.org 1438496968 3472 80.91.229.3 (2 Aug 2015 06:29:28 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 2 Aug 2015 06:29:28 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBQHR62WQKGQEIWRXCKQ@isocpp.org Sun Aug 02 08:29:23 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f70.google.com ([209.85.220.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZLmlv-0004a6-61 for gclcip-std-proposals@m.gmane.org; Sun, 02 Aug 2015 08:29:23 +0200 Original-Received: by pacom8 with SMTP id om8sf203605857pac.3 for ; Sat, 01 Aug 2015 23:29:21 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:content-type:message-id:mime-version :subject:date:references:to:in-reply-to: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=hR6W4ioN4xR4nADocQbnUGNotw86MbwGGcZkIDBEJiA=; b=By3/XwZHenzrrGWDhJ72gInO16DcZ/quJu8BOmJg+aMxPeML+BlNHD8Po1Pmnoi0U/ KqQcFZH8lYze6zjorWEcmJClQaUrwqmLLLilNqY/qUeVvA3mfQI6dkJn24xBjLnzXmgR dh4g4qZBaQUQvKdAVvkkctnEa5yx+YTYXCH9Kuwkl8xYqKFL6ula4Olu/HEa3p/1F3EN DqFpHaNUnVAOqnWs4/NyO6O6By7JEh5qlO3QwcbNgfIoOYLgt6Dvpn8SAwniOb4Ygn1T umPAxO5ZnCOWEYUouhZcUFHylcmreELal8bAM+ARnyNyL9eKF7Tm1vFDrVyPjsDIUvRJ BVuA== X-Gm-Message-State: ALoCoQkYxRP3B5XIQFfshOHR7CaaWxJsFA6qb/IZqPD7WulOo8ERB5FemucE3haYTYlY/JsnaYpL X-Received: by 10.67.23.138 with SMTP id ia10mr10749224pad.18.1438496961324; Sat, 01 Aug 2015 23:29:21 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.162.17 with SMTP id l17ls1387654ioe.19.gmail; Sat, 01 Aug 2015 23:29:20 -0700 (PDT) X-Received: by 10.66.63.8 with SMTP id c8mr24794858pas.122.1438496960588; Sat, 01 Aug 2015 23:29:20 -0700 (PDT) Original-Received: from mail-pa0-x229.google.com (mail-pa0-x229.google.com. [2607:f8b0:400e:c03::229]) by mx.google.com with ESMTPS id kk7si20215134pab.132.2015.08.01.23.29.20 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 01 Aug 2015 23:29:20 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c03::229 as permitted sender) client-ip=2607:f8b0:400e:c03::229; Original-Received: by pabkd10 with SMTP id kd10so65873740pab.2 for ; Sat, 01 Aug 2015 23:29:20 -0700 (PDT) X-Received: by 10.66.65.229 with SMTP id a5mr24568337pat.11.1438496960513; Sat, 01 Aug 2015 23:29:20 -0700 (PDT) Original-Received: from [172.20.10.2] ([121.54.54.186]) by smtp.gmail.com with ESMTPSA id om5sm3834695pbb.37.2015.08.01.23.29.17 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 01 Aug 2015 23:29:19 -0700 (PDT) In-Reply-To: <30f59ec7-0712-48fb-9df0-d66e3fe80c3c@isocpp.org> X-Mailer: Apple Mail (2.2098) X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:400e:c03::229 as permitted sender) smtp.mail=potswa@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=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:19523 Archived-At: --Apple-Mail=_DD0B3623-5087-4177-B5D5-58D786462855 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 > On 2015=E2=80=9308=E2=80=9302, at 1:23 PM, denis bider wrote: >=20 > It strikes me that the language relatively desperately needs a function l= ike try_realloc. This function would work like realloc, except that it woul= d guarantee to fail if memory can't be reallocated in place. >=20 > It seems to me that, even if property like is_relocatable or is_location_= agnostic is introduced, allowing use of realloc with containers of such typ= es, a function like try_realloc would be remain highly useful for container= s of other types. It would avoid having to deep-copy objects if memory can = be reallocated in place. >=20 > On Windows, this is already available like this: >=20 > HeapReAlloc(GetProcessHeap(), HEAP_REALLOC_IN_PLACE_ONLY, p, n); It would be nice to have members in std::allocator_traits, called grow_allo= cation and shrink_allocation. They could simply return false by default, to= indicate failure. I wrote a very fast tokenizer, a while back, using a custom string class wh= ich reserved maximum space on construction, and shrink to fit when the next= token was found. I had to depart from the standard allocator model and rol= l my own string class. It really should be doable with the standard library= .. Sooner or later, if nobody else proposes it, I will. --=20 ---=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --Apple-Mail=_DD0B3623-5087-4177-B5D5-58D786462855 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=UTF-8
On 2015=E2=80=9308= =E2=80=9302, at 1:23 PM, denis bider <isocppgroup@denisbider.com> wrote:

It strikes me that the language relatively desperatel= y needs a function like try= _realloc. This function would work like realloc, except that it would guarantee to fail = if memory can't be reallocated in place.

It seems to me that, even if property like is_relocatable or is_location_agnostic is i= ntroduced, allowing use of = realloc with containers of such types, a function like&nbs= p;try_realloc would = be remain highly useful for containers of other types. It would avoid havin= g to deep-copy objects if memory can be reallocated in place.

On Windows, this is already av= ailable like this:

HeapReAlloc(GetProcessHeap(), HEAP_REALLOC_IN_PLACE_ONLY, p, n);

It would be nice to have me= mbers in std::allocator_traits, ca= lled grow_allocation and shrink_allocation. They could simply return= false by default, to indicate fai= lure.

I wrote a very fast tokenizer, a = while back, using a custom string class which reserved maximum space on con= struction, and shrink to fit when the next token was found. I had to depart= from the standard allocator model and roll my own string class. It really = should be doable with the standard library.

=
Sooner or later, if nobody else proposes it, I will.

--

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