220 34937 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 08:48:48 +0200 Lines: 102 Approved: news@gmane.org Message-ID: References: <0a8293b4-3246-47a5-9881-bc1ca4b91772@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a114699dc473a40055b9048b4" X-Trace: blaine.gmane.org 1508050138 15016 195.159.176.226 (15 Oct 2017 06:48:58 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 15 Oct 2017 06:48:58 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCUMHC4Z6QGBBUUJRTHQKGQET2JYKKY@isocpp.org Sun Oct 15 08:48:52 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wr0-f198.google.com ([209.85.128.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e3cj5-00029K-Jz for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id y85sor1229146wmd.52.2017.10.14.23.48.50 for (Google Transport Security); Sat, 14 Oct 2017 23:48:50 -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 10.28.109.23 with SMTP id i23mr4591097wmc.32.1508050129597; Sat, 14 Oct 2017 23:48:49 -0700 (PDT) Original-Received: by 10.223.173.203 with HTTP; Sat, 14 Oct 2017 23:48:48 -0700 (PDT) Original-Received: by 10.223.173.203 with HTTP; Sat, 14 Oct 2017 23:48:48 -0700 (PDT) In-Reply-To: <0a8293b4-3246-47a5-9881-bc1ca4b91772@isocpp.org> 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=R5iWOSTz; 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:34937 Archived-At: --001a114699dc473a40055b9048b4 Content-Type: text/plain; charset="UTF-8" On Oct 14, 2017 10:14, "Mingxin Wang" wrote: Specifically, in order to define a "concrete memory resource", I suggest to add the following concept: A type MR meets the MemoryResource requirements if the following expressions are well-formed and have the specified semantics (mr denotes a value of type MR). mr.allocate(bytes, alignment) Requires: The types of `bytes` and `alignment` are both `std::size_t`. Returns: A pointer to allocated storage with a size of at least `bytes`. The returned storage is aligned to the specified `alignment`, if such alignment is supported; otherwise it is aligned to `max_align`. Throws: Appropriate exception if it is unable to allocate memory with the requested size and alignment. mr.deallocate(p, bytes, alignment) Requires: The type of `p` is `void*`, the type of `bytes` and `alignment` are both `std::size_t`; `p` shall have been returned from a prior call to `allocate(bytes, alignment)` on a memory resource equal to `*this`, and the storage at `p` shall not yet have been deallocated. Effects: Dispose of allocated storage. Throws: Nothing. It is non-standard but my memory library provides an allocator concept similar to those you've described. You can find it here: github.com/foonathan/memory. I agree that making the PMRs polymorphic by default wasn't an ideal choice. They should have been template based and provide a type erasure wrapper. However, I've heard that the virtual overhead doesn't really matter much. -- 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/CAEddoJZzSZ5RROJ6Uu%3D2%2BR90mXi%2BhnHPDCxobrHM2daM6AxPVw%40mail.gmail.com. --001a114699dc473a40055b9048b4 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On O= ct 14, 2017 10:14, "Mingxin Wang" <wmx16835vv@163.com> wrote:
Specifically, in order to define a "concrete memory reso= urce", I suggest to add the following concept:

A type MR meets the MemoryResource requirements if the following expressi= ons are well-formed and have the specified semantics (mr denotes a value of= type MR).

mr.allocate(bytes, alignment)
=C2=A0 Requires: The types of `bytes` and `alignment` are both `std::size_= t`.
=C2=A0 Returns: A pointer to allocated storage with a size of= at least `bytes`. The returned storage is aligned to the specified `alignm= ent`, if such alignment is supported; otherwise it is aligned to `max_align= `.
=C2=A0 Throws: Appropriate exception if it is unable to alloca= te memory with the requested size and alignment.

m= r.deallocate(p, bytes, alignment)
=C2=A0 Requires: The type of `p= ` is `void*`, the type of `bytes` and `alignment` are both `std::size_t`; `= p` shall have been returned from a prior call to `allocate(bytes, alignment= )` on a memory resource equal to `*this`, and the storage at `p` shall not = yet have been deallocated.
=C2=A0 Effects: Dispose of allocated s= torage.
=C2=A0 Throws: Nothing.

<plug>
It is non-standard = but my memory library provides an allocator concept similar to those you= 9;ve described. You can find it here: github.com/foonathan/memory.
</plug= >

I agree that making= the PMRs polymorphic by default wasn't an ideal choice. They should ha= ve been template based and provide a type erasure wrapper.

However, I've heard that the virtual= overhead doesn't really matter much.

--
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--001a114699dc473a40055b9048b4-- .