220 38229 article Path: news.gmane.org!.POSTED!not-for-mail From: "dgutson ." Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: memcpy/memset/etc overloads for volatile memory Date: Sun, 27 May 2018 21:07:07 -0300 Lines: 147 Approved: news@gmane.org Message-ID: References: <420b274b-fc4b-413e-8ce9-b78131c782f7@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="000000000000cb4a18056d38e68f" X-Trace: blaine.gmane.org 1527465918 26901 195.159.176.226 (28 May 2018 00:05:18 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 28 May 2018 00:05:18 +0000 (UTC) To: std-proposals Original-X-From: std-proposals+bncBDE3NBMV6UFBBOMQVXMAKGQEK5Y2UWI@isocpp.org Mon May 28 02:05:14 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qk0-f200.google.com ([209.85.220.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fN5ex-0006sD-Ki for gclcip-std-proposals@m.gmane.org; Mon, 28 May 2018 02:05:11 +0200 Original-Received: by mail-qk0-f200.google.com with SMTP id 5-v6sf9608344qke.19 for ; 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[209.85.220.65]) by mx.google.com with SMTPS id 56-v6sor16749382qvi.6.2018.05.27.17.07.21 for (Google Transport Security); Sun, 27 May 2018 17:07:21 -0700 (PDT) Received-SPF: pass (google.com: domain of danielgutson@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; X-Received: by 2002:a0c:9621:: with SMTP id 30-v6mr9722026qvx.127.1527466041230; Sun, 27 May 2018 17:07:21 -0700 (PDT) In-Reply-To: X-Original-Sender: danielgutson@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=dTDZL1EF; spf=pass (google.com: domain of danielgutson@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=danielgutson@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE 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:38229 Archived-At: --000000000000cb4a18056d38e68f Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable El dom., 27 de mayo de 2018 21:02, j c escribi= =C3=B3: > > > On Monday, May 28, 2018, Niall Douglas wrote: > >> On Friday, May 18, 2018 at 9:41:08 PM UTC+1, dgutson wrote: >>> >>> This might be interesting. >>> >>> In some systems, the implementation of memcpy() & friends cannot be use= d >>> for memory-mapped devices. >>> Usually, mapped memory is marked as volatile. >>> >>> I'm proposing to add volatile pointers overloads for the memcpy() >>> function and friends, without specifying exactly what should be differe= nt >>> at the standard-level, but allowing implementations to provide a partic= ular >>> behavior. I'm just proposing to add the declaration to the standard. >>> >>> Just there this weekend I, yet again, had to write a custom memcpy() >> implementation because the built-in one can be elided by the compiler >> during optimisation. I'd like to stop having to write memcpy() personall= y. >> >> I think your idea has two variants: >> >> 1. Cannot be optimised out memcpy/memset/memmove etc. I'd suggest >> secure_memset(), secure_memcpy(), secure_memmove() and so on rather t= han >> editions taking a volatile pointer. >> 2. Said routines, but with additional std::memory_order parameter >> >> > Or just stop compilers from doing daft things > FWIW, from my previous team: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D69976 --=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 > 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/CAFQaeCD83_F= BX4cAE%2B9AAEHai4ciCeOaorHY1K94k_Yb0e9wnA%40mail.gmail.com > > . > --=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/CAFdMc-1x-jV8fwXj7%3DS5-XjA1yMTNVBJYQiwpNVO52-Sk= 4X6CQ%40mail.gmail.com. --000000000000cb4a18056d38e68f Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


= El dom., 27 de mayo de 2018 21:02, j c <james.a.cooper@gmail.com> escribi=C3=B3:


On Monday, May 28, 2018, Niall Douglas <= ;nialldouglas14@gmail.com> wrote:
On Friday, May 18, 2018 at 9:41:08 PM UTC+1, dgutson= wrote:
This might = be interesting.

In some systems, the implementation of m= emcpy() & friends cannot be used for memory-mapped devices.
U= sually, mapped memory is marked as volatile.

I'= ;m proposing to add volatile pointers overloads for the memcpy() function a= nd friends, without specifying exactly what should be different at the stan= dard-level, but allowing implementations to provide a particular behavior. = I'm just proposing to add the declaration to the standard.
Just there this weekend I, yet again, had t= o write a custom memcpy() implementation because the built-in one can be el= ided by the compiler during optimisation. I'd like to stop having to wr= ite memcpy() personally.

I think your idea has two= variants:
  1. Cannot be optimised out memcpy/memset/memmove = etc. I'd suggest secure_memset(), secure_memcpy(), secure_memmove() and= so on rather than editions taking a volatile pointer.
  2. Said routine= s, but with additional std::memory_order parameter

Or just stop compilers from doing daft things= =C2=A0


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