220 37359 <22ef47e6-e957-4519-820f-1decb09a116d@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: `offsetof` in a macro-less, modular world Date: Fri, 16 Mar 2018 08:16:45 -0700 (PDT) Lines: 81 Approved: news@gmane.org Message-ID: <22ef47e6-e957-4519-820f-1decb09a116d@isocpp.org> References: <71ed1718-d272-4920-92fe-3b59750e6fb8@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1144_1649908020.1521213405837" X-Trace: blaine.gmane.org 1521213287 13095 195.159.176.226 (16 Mar 2018 15:14:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 16 Mar 2018 15:14:47 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBXV7V7KQKGQEGIE2RKI@isocpp.org Fri Mar 16 16:14:43 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f72.google.com ([209.85.213.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ewr44-0003Fn-NP for gclcip-std-proposals@m.gmane.org; Fri, 16 Mar 2018 16:14:40 +0100 Original-Received: by mail-vk0-f72.google.com with SMTP id l81sf6411311vkd.18 for ; Fri, 16 Mar 2018 08:16:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=/1y48GsbLvgzQKbGzgeyaTiJnMx5G3qTcuDmFnq8JN0=; b=N5KE8ZL2cS0kiOn6q6OtG2bx0ytSxgcvZGCERcpuaK2cjMfyktCQZj3nLWeNGAjCyS 81Vk2nnoObdrC6bvZzPvYzzp89YmXnibG8PyO6u13dzHXd5bPEOL8EY/H+hUbMN21Btt AUhl4bX3uakFmJU/xa7B1YmwejObgh4sWS57D6eprQMM+PlyuEV/awCrhnzjJxos54jP 7gRAhtT0YQVUt0ITvNcSZZSGEDNUKR8x7avS7C2LE3H64Iavvk+BIeoj98lgFdWZ7UtX EhcSmeFZJjBSLfbVyewYjovNkZgz51d9LX+icJlJvZ8/oWEDSlEVe/a+LWxuowzR8+lC hj4Q== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=/1y48GsbLvgzQKbGzgeyaTiJnMx5G3qTcuDmFnq8JN0=; b=sMqmlnIsw0oYoXjjVC+rXT9bTMG9TsUs1dJZoG32F2oP3iIB6Y6pMdkIoYvE/n4YAd NaEUKh2isdzh6GT7lFy+U/mvVT7pLescOejQU4utmibFMzx9UAYlOjvSkTzVDT+X6RQr XrsW31XhI8UEMHX1jwzHDnxb5w2gts87Xv7tUf40bOidvSQhLvITPGgto1mYzy1rEiax /V8/TbRENRJ8EGytOnqvf2zHtiOpToQYDaTod/mq2EBIW0N5BP08+sowOIySbcUf+b3p 6gOsuATYSZoogmDcC0e0UNAtMIs55wAvl1//CH1KpnQ2ezqXSHAM+vvw423L1Gt9Crdd q9VQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=/1y48GsbLvgzQKbGzgeyaTiJnMx5G3qTcuDmFnq8JN0=; b=m7SAjpVAHil8iAQ8gJgzCXsmN7y2e8kV5gBqsYyeJag48yRcl6vX8pTC5+vAbKKHaR RyFFZxP/qJQpInSDUav8cOBx5CFUwBvECr10Cc9BQ7anBAsp1VXFW1cdwOAKRa/0cIiA YJVvPyk4pUs9roKefYlpox6j4OoNGSPyzcx1x3UhGdayg0AXsgZkItmzEbyHg27P1biO bOZ3Gy779Pco/Y16i+nY2ypYHjNllEJdHG4ijDlC499vFTtOcv+0b9TWHrRL1zU4as3s dOPYWiGj8adLlLLeQ5AK2p+M9sTNVGoA50HdOIycFUkjESNC6b301vo9UR6IxEr+EQfc ZTtg== X-Gm-Message-State: AElRT7HeyKisWQOu/8voijFNp1hL+Nwu+vAOB0j2RqARjd5Ap2atv8zz CB1KanQaBGuRKyPoeBJxJpOSWg== X-Google-Smtp-Source: AG47ELtHjS3RFRPhd0H4ACmxj73TqLFtWI4AibpuVqUGjXOD7fqeyStQNEILZS6u+CYq6pq2rjTSrQ== X-Received: by 10.31.252.70 with SMTP id a67mr919067vki.11.1521213407711; Fri, 16 Mar 2018 08:16:47 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.31.50.79 with SMTP id y76ls3909960vky.7.gmail; Fri, 16 Mar 2018 08:16:46 -0700 (PDT) X-Received: by 10.31.151.87 with SMTP id z84mr247914vkd.5.1521213406258; Fri, 16 Mar 2018 08:16:46 -0700 (PDT) In-Reply-To: X-Original-Sender: jmckesson@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:37359 Archived-At: ------=_Part_1144_1649908020.1521213405837 Content-Type: multipart/alternative; boundary="----=_Part_1145_1684924087.1521213405838" ------=_Part_1145_1684924087.1521213405838 Content-Type: text/plain; charset="UTF-8" On Friday, March 16, 2018 at 10:54:35 AM UTC-4, Hyman Rosen wrote: > > On Thu, Mar 15, 2018 at 11:55 PM, Nicol Bolas > wrote: >> >> The problem I'm talking about here is that if you have a `std.cstddef` >> module, without the ability to export macros, it cannot export anything >> which is compatible with `offsetof` usage. So even if we make an operator >> for this or empower member pointers or whatever, the existence of such a >> feature won't allow you to switch from `#include ` to `import >> std.cstddef` without changing your code. >> > > You just need to simultaneously modify C++ so that there is a built-in > equivalent > to offsetof, and make offsetof a pre-defined macro that expands to that. > And if modules can't export macros, how will `import std.cstddef` give me access to that module? -- 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/22ef47e6-e957-4519-820f-1decb09a116d%40isocpp.org. ------=_Part_1145_1684924087.1521213405838 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Friday, March 16, 2018 at 10:54:35 AM UTC-4, Hy= man Rosen wrote:
On Thu, Mar 15, 2018 at 11:55 PM, Nicol = Bolas <jmck...@gmail.com> wrote:
The problem I'm talking about h= ere is that if you have a `std.cstddef` module, without the ability to expo= rt macros, it cannot export anything which is compatible with `offsetof` us= age. So even if we make an operator for this or empower member pointers or = whatever, the existence of such a feature won't allow you to switch fro= m `#include <cstddef>` to `import std.cstddef` without changing your = code.

You just need to simultaneously modi= fy C++ so that there is a built-in equivalent
to offsetof, and make offs= etof a pre-defined macro that expands to that.

And if modules can't export macros, how will `import s= td.cstddef` give me access to that module?

--
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 https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/22ef47e6-e957-4519-820f-1decb09a116d= %40isocpp.org.
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