220 37456 article Path: news.gmane.org!.POSTED!not-for-mail From: Hyman Rosen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Why do we need `volatile` in C++? Date: Sun, 25 Mar 2018 13:26:54 +0000 Lines: 70 Approved: news@gmane.org Message-ID: References: <044dfdd3-2313-4ce3-a5e2-3a23c1c0d678@isocpp.org> <1622054.9qo2sSbJHP@tjmaciei-mobl1> <8f73ba25-08d7-40a7-9bf8-9adf7cb9235f@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="001a114b332c0d25d205683c9d67" X-Trace: blaine.gmane.org 1521984305 9078 195.159.176.226 (25 Mar 2018 13:25:05 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 25 Mar 2018 13:25:05 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDKJJPVBQMKRBK6H33KQKGQEOCFO66Q@isocpp.org Sun Mar 25 15:25:01 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wr0-f200.google.com ([209.85.128.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1f05ds-0002F1-SM for gclcip-std-proposals@m.gmane.org; Sun, 25 Mar 2018 15:25:00 +0200 Original-Received: by mail-wr0-f200.google.com with SMTP id m7sf2362817wrb.16 for ; Sun, 25 Mar 2018 06:27:08 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1521984428; cv=pass; d=google.com; s=arc-20160816; b=rbhSDSD/bA9dnTRzSoI1fKMFLxJsrymKFIfx1m2EcHXQbiNE2BDxQ0lSRnATiSnwBx eOh7pREuTy99yuad7uj7pO2iF8i6I745C1mPe945/cVdPF+4/2Xj5o8f3vU6xjO3/6tB JMQNAdFGlNZR+DGEIEX31NF5uVkXTzgpojFhROC+jP6MPSO6g/LitRB37wfD4s5ngSQU WerMzXp03lITsXN/f3A2H58jLgFDbYTKR0C8RV3T6sX8MmtA1eiqFLbYVe1kifrBE6Ef a/vyPVrEiXIt1qKTuNOooigHBxqseY4/812p8qgETnntEa4g49Br61T3FtEcFg/ddutT pkrQ== 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:to:subject:message-id:date :from:in-reply-to:references:mime-version:arc-authentication-results :arc-message-signature:dkim-signature:arc-authentication-results; bh=PuqrmXNG+YV1ztFmfmEgLyZ7ajLP5dWSNerE+Eg37fg=; b=ibg5dqOnkpFLaImJJrdaRt6k3qJbnEqWHxxFjsWUjxID9Q6aOCvRSTM+PeJUD3FPe7 sRmLmdGgZFEldTikN6m9NKbfyWdpZG3EwbPIRUW6yTQ2ZCtnVByfhiOfPxhKC53We+U7 6BNFAjVkOLT4vBndVxUHk1qSE0TBfV3nAowTmt2b2jHtNyn8h4212m9KyU65wF1lwRGB IftowX/gJ4RRgpnA5bQ71wuftwERvayDnUxGDYfoicx6HQg3UGnS+XofOFeqeLRGLdQo /0KCyL5hQFdI7v/ewbmkCgmz9AK6x4RelNaH6E2I8VxFzbRHkyfBSKX5LAMdwISudX9V B9KQ== ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=FSELQY03; spf=pass (google.com: domain of hyman.rosen@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hyman.rosen@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE 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=mime-version:references:in-reply-to:from:date:message-id:subject:to :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=PuqrmXNG+YV1ztFmfmEgLyZ7ajLP5dWSNerE+Eg37fg=; b=UYzxm7Jjf5ArG1RktPv/jb+s1Sp/LJ3GPARsy402TXT1wPQ0Zf97+4tr9DPzf3dra1 gedOwBvwmouqXLZIh3uWhIzThJxlG9u79HQyqtQt6xja17+Z/sBvVr1yBhKtMzSmsOj1 EkDNXkaUWwCV+w89p1wrCsAZWRocRHZEOw0Z/HIkrkn8Cn3GEeBcoyR+qU6JzLZgYoHw DrY5nBtNlXLnJDC9byroCyaoiQOSiIVQS4tRDFBaO+VUnCcE2+EUKxL9Jiv82zdbp1W1 9oWcC6ssMb/uXeE2S0DbmdRd7ZmfIUO/sAbI2s35cpbC+J4pGHIV1PNXmt1xBEvycFoc +wzA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject: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=PuqrmXNG+YV1ztFmfmEgLyZ7ajLP5dWSNerE+Eg37fg=; b=rLd8rc8wt7oT0pRGUO+d1zGkHEbqTObY829I3IU8ZrlkC+sni7pKaZ3vPMCFFRNRha Au6qvoEppfpmMGMMHqOMX3Zn+ahz6cQq+Jy/eIBW+Krstla5I6r9TaNhgEwKoWtRuo64 mI360v9tO92v90M97CylYumcrgR48qNFPBLp7zGZmoNa6KfGJQZWnWDCBm1bS9V1yT7y CoU9Vri4QbgJt1Cz44R05XU+LV7WK1JKfiqOlVtH7S8JZ41rDodUdXJ/qrSZ5FDRZOfF Bob388FzQhpDSeQ/1K3CcGPBwFXGfE1wm+pNvLIThF7EtT028LsES2h+RDZfEPe7uxZk vLhQ== X-Gm-Message-State: AElRT7HHQYL2Vug/ak7bx8QC7vcGbjbMvKlZzPRXqJEDF3g+uKjiPXH+ IGDdahDtKXWu+CWAgEi1x4fAbg== X-Google-Smtp-Source: AG47ELuvaguYZPFj//7Nz07dGS5u8A+EwN0njH0zzlS642Zl3kcmDMX6x8q8uXHnVgfrwVOGlJirDQ== X-Received: by 10.28.20.18 with SMTP id 18mr1655448wmu.22.1521984428200; Sun, 25 Mar 2018 06:27:08 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.134.67 with SMTP id i64ls174204wmd.2.gmail; Sun, 25 Mar 2018 06:27:06 -0700 (PDT) X-Received: by 10.28.195.67 with SMTP id t64mr10054596wmf.113.1521984426564; Sun, 25 Mar 2018 06:27:06 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1521984426; cv=none; d=google.com; s=arc-20160816; b=RAomDlmkdCANoBA32o5faCOsOu6t9+iKERYpU937bIAZ6kyx275TtfMvgk3sQWcsNE h6pZhQ/th7bOJzICO9MeKXNKILG0m/mYmmVz3G34KZUb/1e3sVLzzcwM8mRjm11QbkLK Qrg5CjjZGVRL0l39IpEqH4KcTivwcIf2BwM3BdJkChxu2jwNRoSjUJWkxWEjscuh5sWE Az6iaaD4JpOQAkWW4cmx1QlfdUQI0b9yMcxuKir0+p6k0UyLT6cyksxvdR9kwHiiGNC+ pq7j0F/5zOKly3zCXdjfV081ZbObyj30r595OPM4emRv3Rxzrmx708XW1Gej8UzJNGjZ K2wQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=to:subject:message-id:date:from:in-reply-to:references:mime-version :dkim-signature:arc-authentication-results; bh=1vrxn5S6oKbv3xaIgMnII71HvG/yVMlSpzORA/ok0Bo=; b=gscdsCXg14bpoiPvkR2FZprbgbLp2zHgka5F3MWZuOZauOlTaZe7/b3Q0j7Ud4oKL4 KGhIb3weVAnuahR87sjPdSJK8fTDsFjskuEHncQkh64QrDxEVYXnH5uNn4rFQYvi9vY8 +ZP4YaJ3PKiPjEUbiEbw4pf0s+s86atmW7V01EYGRypEDsv80argbJMQMXd9cRCPl3KF EwLwyjHArUFLmsYsNPWC06GjXIDh+cE8Fa/mH2DwzcR0QYAc1iS+dHn9MKZLTF197eNv r5PE5myu415rLX0QVZlIQVjJ8jyHlRlrzxmMEIXPc5gwk1iourEV8tozwS71NE4GmEds IWDQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=FSELQY03; spf=pass (google.com: domain of hyman.rosen@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hyman.rosen@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE 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 f14sor3637402wmi.51.2018.03.25.06.27.06 for (Google Transport Security); Sun, 25 Mar 2018 06:27:06 -0700 (PDT) Received-SPF: pass (google.com: domain of hyman.rosen@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.28.101.6 with SMTP id z6mr11817325wmb.110.1521984425762; Sun, 25 Mar 2018 06:27:05 -0700 (PDT) In-Reply-To: <8f73ba25-08d7-40a7-9bf8-9adf7cb9235f@isocpp.org> X-Original-Sender: hyman.rosen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=FSELQY03; spf=pass (google.com: domain of hyman.rosen@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hyman.rosen@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:37456 Archived-At: --001a114b332c0d25d205683c9d67 Content-Type: text/plain; charset="UTF-8" On Sun, Mar 25, 2018, 8:52 AM Bengt Gustafsson < bengt.gustafsson@beamways.com> wrote: > While all of this is true volatile sees very little use compared to its > rather large effects on the standard. I'm pretty sure that if we had a > fresh start > handling of memory mapped IO would be relegated to a few library > intrinsics. > I've had to use volatile distressingly often, and it has nothing to do with memory-mapped IO. I use it to force assignments to floating-point variables to be written to memory, denying the compiler permission to use the value from an extended-precision register instead. Volatile can go only when this permission is revoked (or gcc is changed to obey the rules properly, which won't happen because of optimizationism). > -- 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/CAHSYqdYiQvDvijZVMhpV%3D4k_nv3S8oZbrxXWPwjjCH0KmK4LXQ%40mail.gmail.com. --001a114b332c0d25d205683c9d67 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
= On Sun, Mar 25, 2018, 8:52 AM Bengt Gustafsson <bengt.gustafsson@beamways.com> wrote:
While all of this is tr= ue volatile sees very little use compared to its rather large effects on th= e standard. I'm pretty sure that if we had a fresh start
handling o= f memory mapped IO would be relegated to a few library intrinsics.

I&#= 39;ve had to use volatile distressingly often, and it has nothing to do wit= h memory-mapped IO.=C2=A0 I use it to force assignments to floating-point v= ariables to be written to memory, denying the compiler permission to use th= e value from an extended-precision register instead.=C2=A0 Volatile can go = only when this permission is revoked (or gcc is changed to obey the rules p= roperly, which won't happen because of optimizationism).

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
To view this discussion on the web visit h= ttps://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAHSYqdYiQvDvij= ZVMhpV%3D4k_nv3S8oZbrxXWPwjjCH0KmK4LXQ%40mail.gmail.com.
--001a114b332c0d25d205683c9d67-- .