220 39414 article Path: news.gmane.org!.POSTED!not-for-mail From: =?UTF-8?B?R2HFoXBlciBBxb5tYW4=?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Alternative proposal for mapping P0709 Deterministic Exceptions into C Date: Thu, 26 Jul 2018 10:24:16 +0100 Lines: 170 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/alternative; boundary="0000000000005b76090571e3906d" X-Trace: blaine.gmane.org 1532596952 26598 195.159.176.226 (26 Jul 2018 09:22:32 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 26 Jul 2018 09:22:32 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDRYVJ6TVYBRBVNG43NAKGQE3BTXKWA@isocpp.org Thu Jul 26 11:22:28 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf1-f71.google.com ([209.85.167.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1ficTb-0006pz-Ua for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id 96-v6sor84733lfu.11.2018.07.26.02.24.37 for (Google Transport Security); Thu, 26 Jul 2018 02:24:37 -0700 (PDT) Received-SPF: pass (google.com: domain of gasper.azman@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a19:eb1b:: with SMTP id j27-v6mr891732lfh.0.1532597076979; Thu, 26 Jul 2018 02:24:36 -0700 (PDT) Original-Received: by 2002:ab3:416:0:0:0:0:0 with HTTP; Thu, 26 Jul 2018 02:24:16 -0700 (PDT) In-Reply-To: X-Original-Sender: gasper.azman@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=naHKWWKH; spf=pass (google.com: domain of gasper.azman@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=gasper.azman@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:39414 Archived-At: --0000000000005b76090571e3906d Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Niall, Do you have an updated version of your mechanism paper? Among my colleagues, there is a lot of informal interest that Herb's paper just doesn't address - and your paper is really good for shutting down FUD. If you do, could you ping it through here? Thanks, Ga=C5=A1per On Wed, Jul 25, 2018 at 8:47 PM, Niall Douglas wrote: > 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 eas= e > 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 C2= 2 >>> 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 > > . > --=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/CAANG%3DkXwsh37OYXvLrfTo8oFuW3q%2BxR-DheGYTN%2BD= kUzwWVziA%40mail.gmail.com. --0000000000005b76090571e3906d Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Niall,

Do you have an updated version o= f your mechanism paper? Among my colleagues, there is a lot of informal int= erest that Herb's paper just doesn't address - and your paper is re= ally good for shutting down FUD.

If you do, could = you ping it through here?

Thanks,

Ga=C5=A1per

On Wed, Jul 25, 2018 at 8:47 PM, Niall Douglas <= nialldouglas14@gmail.com> wrote:
But in s= hort, C22 _Fails(T) maps directly onto C++ 23 throws(T).
=

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

<= div>What you're looking for is `throws{T}`. Which P0709 treats as an ex= tension, not a required part of the proposal. So there's no guarantee i= t will make it into any hypothetical C++23.
There may be some movement on that next revision of P07= 09 in order to ease things for WG14.
=C2=A0

The only difference is auto-prop= agation, so a _Fails(T) if unhandled results in a failure to compile, where= as a throws(T) if unhandled propagates upwards.

Th= is 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 inco= rporate 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 c= onvenors of WG14 and WG21 want coevolution on this feature, especially as i= t 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.

<= /div>
Niall

--
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-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/fa71= 557a-d506-4f1d-b39e-590f337b8ae3%40isocpp.org.

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