220 39409 article Path: news.gmane.org!.POSTED!not-for-mail From: Niall Douglas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Alternative proposal for mapping P0709 Deterministic Exceptions into C Date: Wed, 25 Jul 2018 12:47:03 -0700 (PDT) Lines: 112 Approved: news@gmane.org Message-ID: References: <6a65c934-5d2a-4e75-b88d-9eaaee338bd3@isocpp.org> <1c229827-6d5d-45bd-8766-c3af818b2b0b@isocpp.org> <4ac80882-16fc-4ab4-9a12-64da1ef0e974@isocpp.org> <8866881c-ef1d-4c37-9242-5b1d3327c288@isocpp.org> <363df3db-b747-449f-b95d-81d15b6c3842@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_9439_1083350221.1532548023426" X-Trace: blaine.gmane.org 1532547898 13486 195.159.176.226 (25 Jul 2018 19:44:58 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 25 Jul 2018 19:44:58 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDGKFT5YZADRBOFH4PNAKGQE6MIBKLA@isocpp.org Wed Jul 25 21:44:54 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb0-f197.google.com ([209.85.213.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fiPiQ-0003Pv-I2 for gclcip-std-proposals@m.gmane.org; Wed, 25 Jul 2018 21:44:54 +0200 Original-Received: by mail-yb0-f197.google.com with SMTP id g6-v6sf4577893ybc.5 for ; Wed, 25 Jul 2018 12:47:05 -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=ouuDb8ZnUN6yF2MXvuujy7CTRUWfrgnj+sVufmEjII8=; b=vNfQapRZ65l4YEUSckxbcKXyv98DNwgwVpIiODWNitNOlpkviqWD9BUblFI5DChsLA E3NXJhjtApBJKIpmCjgYSMPQRO9xQqLXS4WQalRp61SJFgQQXrUNbYzLgEZShRffnInk XWefwRcigbkosSAKyrgChQCunX4lKA4BDgR2MAs5IgNEB77JawMkg6B2lXmUg3lQ4Aal CwrHMwRtMt7hB+k7Pjh+Ox8k1OUsBYuMo3ottni+2zA+Nt+SiMg1H5YONl7W67+xwHxK fU7yhm+YmmXg5c8+NL6uD40sFqvzThY2f9qyOcjQc/n+DOlyt5cHJH76ZZkWwdXm8IaA 1ryw== 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=ouuDb8ZnUN6yF2MXvuujy7CTRUWfrgnj+sVufmEjII8=; b=k/OQYPJVZNfDxOWkhxwCNK/nydrMf3ZS0ecIV0pkyTtPtJ78Br7vHSbvA0ZrHAnB59 Eq6JFLwQWDVzgQ4cW2Qv/Ok+gV1SDPJaS31N9TUMLmX7TjNMjEkVMYXPEkttrgTsXsi0 PXc+7LYWjppjNlNrNRssgeMm7MXhWuJgrN5JPAYWykuvuCpxqjfQiOCEt0dwHC117WPw R1q7FMfO45dZ0k5LJaeDyC+Gn9nBUsxH3JsUy2rlY79MVPgeLs3DRTkrjoK2sOzn7L5m LVicgm8PERqhz+gw9giAT4/xcBIXZfKm476hR2Ai3sAp0ghMVqULGXc9dNzFWkaP5PI0 d8VQ== 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=ouuDb8ZnUN6yF2MXvuujy7CTRUWfrgnj+sVufmEjII8=; b=Kxuvq5ZuwXEa9n13NwOo3jsGua5LN0FTFmXsjGKqrqG5NffRQAwXFIbEOpV/x86J/y 0EZ3iFbmJGoBjtISYUPmTz+8I3E/esqLDCBh3iLeF2woJRF0Z+pfgUe9Lp2jm3v8WmdM LBj0Eta+uCOisHD/aHVzEfn6eeM0IEyBdebAR3kE1TZqegP0PW7wCikoJDMCFznoYvwV w6jHC99i/DBdrlT7Tq9kIprstowen/FhOckSmT4biIo3K2+3ELwnRGJVo21zbqOC7IBT 0n+CZ8B6DVbdWaudDCDgZDnFjinisVWPua9AOno9lyhgnZKW/pSZt0H/1xO/Tk8w1HFZ DiCQ== X-Gm-Message-State: AOUpUlGS++fchyK0wFP2Jas4mSjEIm63eaGzP9r1PYdVFD11P+jiIGas s726Itg/WECAnW4CJR5kjYjC8w== X-Google-Smtp-Source: AAOMgpfWzVyKTNFG1rERlsdyPIhDki2UgVgzDsIvFr/YZUdKW3nhIp4FeOfoUWMf1nxNWLxDqnlC4A== X-Received: by 2002:a81:b2c5:: with SMTP id q188-v6mr6156053ywh.5.1532548025117; Wed, 25 Jul 2018 12:47:05 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a25:5502:: with SMTP id j2-v6ls3596896ybb.7.gmail; Wed, 25 Jul 2018 12:47:04 -0700 (PDT) X-Received: by 2002:a25:5f4a:: with SMTP id h10-v6mr377242ybm.5.1532548024004; Wed, 25 Jul 2018 12:47:04 -0700 (PDT) In-Reply-To: X-Original-Sender: nialldouglas14@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:39409 Archived-At: ------=_Part_9439_1083350221.1532548023426 Content-Type: multipart/alternative; boundary="----=_Part_9440_1277428745.1532548023426" ------=_Part_9440_1277428745.1532548023426 Content-Type: text/plain; charset="UTF-8" > > But in short, C22 _Fails(T) maps directly onto C++ 23 throws(T). >> > > Pedantic note: `throws(T)` doesn't exist. `throws()` is a > *conditional* throws declaration, much like `noexcept()`. P0709 > makes that abundantly clear. > > What you're looking for is `throws{T}`. Which P0709 treats as an > extension, not a required part of the proposal. So there's no guarantee it > will make it into any hypothetical C++23. > There may be some movement on that next revision of P0709 in order to ease things for WG14. > > The only difference is auto-propagation, so a _Fails(T) if unhandled >> results in a failure to compile, whereas a throws(T) if unhandled >> propagates upwards. >> >> This is what WG14 asked for. As C++ 23 would surely be incorporating C22 >> into itself, whatever goes into C also goes in C++. >> > > That's not how C++ has worked since 1998. C++11 did not incorporate C99 > wholesale; it only took specific things from it. Similarly, C++14/17/20 did > not adopt C11 wholesale. The two languages are *diverging*. > > So why should we expect C++23 to adopt C22 in this way? > > Both convenors of WG14 and WG21 want coevolution on this feature, especially as it makes it much easier to bring C++ contracts into C. That doesn't mean it will happen of course. But it does mean that right now, that's the aim, until either committee conclusively decides otherwise. Niall -- 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/fa71557a-d506-4f1d-b39e-590f337b8ae3%40isocpp.org. ------=_Part_9440_1277428745.1532548023426 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
But in short, C22 _Fails(T= ) maps directly onto C++ 23 throws(T).

Pedantic note: `throws(T)` doesn't exist. `throws(<expr>)` is a= conditional throws declaration, much like `noexcept(<expr>)`.= P0709 makes that abundantly clear.

What you'r= e looking for is `throws{T}`. Which P0709 treats as an extension, not a req= uired part of the proposal. So there's no guarantee it will make it int= o any hypothetical C++23.

There= may be some movement on that next revision of P0709 in order to ease thing= s for WG14.
=C2=A0

The only difference is auto-propagation, so a _Fails(T) if unhandle= d results in a failure to compile, whereas a throws(T) if unhandled propaga= tes upwards.

This is what WG14 asked for. As C++ 2= 3 would surely be incorporating C22 into itself, whatever goes into C also = goes in C++.

That's not how C++ h= as worked since 1998. C++11 did not incorporate C99 wholesale; it only took= specific things from it. Similarly, C++14/17/20 did not adopt C11 wholesal= e. The two languages are diverging.

So why should we expect C++23 to adopt C22 in this way?
Both convenors of WG14 and WG21 want coevol= ution on this feature, especially as it makes it much easier to bring C++ c= ontracts into C. That doesn't mean it will happen of course. But it doe= s mean that right now, that's the aim, until either committee conclusiv= ely decides otherwise.

Niall

<= /div>

--
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/fa71557a-d506-4f1d-b39e-590f337b8ae3= %40isocpp.org.
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