220 37371 article Path: news.gmane.org!.POSTED!not-for-mail From: inkwizytoryankes@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: `offsetof` in a macro-less, modular world Date: Fri, 16 Mar 2018 15:02:16 -0700 (PDT) Lines: 137 Approved: news@gmane.org Message-ID: References: <71ed1718-d272-4920-92fe-3b59750e6fb8@isocpp.org> <22ef47e6-e957-4519-820f-1decb09a116d@isocpp.org> <64578641-a89f-4b60-82ce-5183a54a3630@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2696_401175840.1521237736111" X-Trace: blaine.gmane.org 1521237615 31464 195.159.176.226 (16 Mar 2018 22:00:15 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 16 Mar 2018 22:00:15 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDDLTAGNTIBBB2P5WDKQKGQE4ATEV4Q@isocpp.org Fri Mar 16 23:00:11 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f69.google.com ([209.85.213.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ewxOV-00087Q-FF for gclcip-std-proposals@m.gmane.org; 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Fri, 16 Mar 2018 15:02:18 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.31.148.12 with SMTP id w12ls4463773vkd.1.gmail; Fri, 16 Mar 2018 15:02:17 -0700 (PDT) X-Received: by 10.31.158.83 with SMTP id h80mr394250vke.9.1521237736948; Fri, 16 Mar 2018 15:02:16 -0700 (PDT) In-Reply-To: <64578641-a89f-4b60-82ce-5183a54a3630@isocpp.org> X-Original-Sender: inkwizytoryankes@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:37371 Archived-At: ------=_Part_2696_401175840.1521237736111 Content-Type: multipart/alternative; boundary="----=_Part_2697_1190768618.1521237736112" ------=_Part_2697_1190768618.1521237736112 Content-Type: text/plain; charset="UTF-8" On Friday, March 16, 2018 at 6:23:12 PM UTC+1, Nicol Bolas wrote: > > On Friday, March 16, 2018 at 11:34:02 AM UTC-4, Hyman Rosen wrote: >> >> On Fri, Mar 16, 2018 at 11:16 AM, Nicol Bolas wrote: >>> >>> 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? >>> >> >> What module? I don't understand. >> >> Let me try again: >> >> - Change C++ so that there is a built-in version of offsetof under a >> different name, say __offsetof. >> - __offsetof is available for use in all C++ code without any header >> or module needed, just as sizeof is. >> - Also change C++ so that offsetof is a pre-defined macro that >> expands to __offsetof. >> >> > Oh, when you said "built-in" you meant like "supplied by the compiler". > > So... what happens with people's code that *don't* include or > that happens to use the `offsetof` identifier? Admittedly this is > a minor issue, as I rather doubt someone's going to make a class or > function that conflicts with a fairly widely known C macro that gets > included by quite a few things (even if only because of other useful > things). > People who use `` will still use `` we don not change antything (this why I suggest leaving it alone). We add new keyword `real_super_offsetof` that will be available everywhere. Only problem would be migration of heder to modules usage but because offsetof is macro we can safely use text replace to change it to new keyword. -- 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/d9e85fb4-6296-44ee-81f8-7b8fdbc8822e%40isocpp.org. ------=_Part_2697_1190768618.1521237736112 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Friday, March 16, 2018 at 6:23:12 PM UTC+1, Nic= ol Bolas wrote:
On Friday, March 16, 2018 at 11:34:02 AM UTC-4, Hyman Rosen wrote:
On Fri, Mar 16, 2018 at 11:16 AM, Nicol Bolas <= jmck...@gmail.com> wrote:
You just need to s= imultaneously modify C++ so that there is a built-in equivalent
to offse= tof, and make offsetof a pre-defined macro that expands to that.

And if modules can't export m= acros, how will `import std.cstddef` give me access to that module?

What module?=C2=A0 I don't understand.
Let me try again:<= br>
  • Change C++ so that there is a built-in version of offsetof under a different name, say __offsetof.
  • __offsetof=C2=A0is available for use in all C++ code without any header o= r module needed, just as sizeof = is.
  • Also change C++ so that off= setof=C2=A0is a pre-defined macro that expands to __offsetof.

Oh, wh= en you said "built-in" you meant like "supplied by the compi= ler".

So... what happens with people's code that don'= ;t include <cstddef> or <stddef> that happens to use the `o= ffsetof` identifier? Admittedly this is a minor issue, as I rather doubt so= meone's going to make a class or function that conflicts with a fairly = widely known C macro that gets included by quite a few things (even if only= because of other useful things).

Peop= le who use=C2=A0 `<cstddef>` will still use `<cstddef>` we don = not change antything (this why I suggest leaving it alone).
We add new k= eyword `real_super_offsetof` that will be available everywhere.
Only pro= blem would be migration of heder to modules usage but because offsetof is m= acro we can safely use text replace to change it to new keyword.
<= /div>

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