220 39390 article Path: news.gmane.org!.POSTED!not-for-mail From: David Brown Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Alternative proposal for mapping P0709 Deterministic Exceptions into C Date: Wed, 25 Jul 2018 09:33:07 +0200 Lines: 78 Approved: news@gmane.org Message-ID: References: <6a65c934-5d2a-4e75-b88d-9eaaee338bd3@isocpp.org> <1c229827-6d5d-45bd-8766-c3af818b2b0b@isocpp.org> <5e1086ff-802e-4e45-bd6c-077a93287b08@isocpp.org> <6a349048-5ffe-4d46-9b6a-d3246e2d505b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1532503873 24996 195.159.176.226 (25 Jul 2018 07:31:13 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 25 Jul 2018 07:31:13 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDP6R2XHXIARBPOP4DNAKGQEYKDNB5I@isocpp.org Wed Jul 25 09:31:09 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lj1-f200.google.com ([209.85.208.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fiEGJ-0006OJ-FX for gclcip-std-proposals@m.gmane.org; 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Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1fiEGH-0006ME-5s for std-proposals@isocpp.org; Wed, 25 Jul 2018 09:31:05 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 64 Original-X-Complaints-To: usenet@blaine.gmane.org In-Reply-To: <6a349048-5ffe-4d46-9b6a-d3246e2d505b@isocpp.org> X-Original-Sender: david@westcontrol.com X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 195.159.176.226 is neither permitted nor denied by best guess record for domain of gclcip-std-proposals@m.gmane.org) smtp.mailfrom=gclcip-std-proposals@m.gmane.org 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:39390 Archived-At: On 24/07/18 16:40, Nicol Bolas wrote: >=20 >=20 > On Tuesday, July 24, 2018 at 5:08:45 AM UTC-4, David Brown wrote: >=20 > On 24/07/18 10:25, Ga=C5=A1per A=C5=BEman wrote: > > If we are to use the function's name, how do we deal with unutterab= le > > functions, like lambdas, or methods? You can dismiss it as "right, = C > > doesn't have those", but they might in the future. I don't think > it's a > > good idea at all. > > > > I also don't like that if I rename the function, I now have to chan= ge > > its body. That makes very little sense to me. A rose by any other > name > > *should* smell as sweet. > > >=20 > Having programmed in Pascal, where you use the function's name as the > return value pseudo-variable, I agree with that - it is a pain. >=20 > It may also be a challenge for recursive functions, and it will > certainly be a problem if you want to use the function more than once > before checking for errors: >=20 > x =3D foo(y) + foo(z); > if (foo.error) ... // Which foo call? >=20 > I appreciate the desire for cheap and standardised error handling, bu= t > this syntax is not going to work. >=20 >=20 > I think the design of this proposal is intended to be much more > conservative than Niall's. In particular, it is /purely/ focused on the > transmission of error codes via this invisible fail state. That is, it's > a mere optimization of what you would otherwise have written in an > error-code-based world. >=20 > If your hypothetical `foo` function had returned an error code, then > there's no way for that `foo(y) + foo(z)` code to work. Therefore, > error-code-based functions wouldn't have been written that way, so > functions under the new paradigm also wouldn't be written this way. There are currently two main ways of handling errors in C++. You can use C-style status returns. In that case, "foo(y) + foo(z)" does not work. But you /know/ it does not work - it is very clear from the way the functions are declared and used. Or you can use exceptions. Then "foo(y) + foo(z)" /does/ work, and it is clear that it works. With this proposal, it looks like "foo(y) + foo(z)" should work, but it does not work. And therein lies the danger. >=20 > Now personally, I think that's basically throwing away a golden > opportunity to more reasonably handle errors in C. But that is the basic > thinking behind the proposal; that kind of compatibility is exactly what > it's going for. The idea is that this is merely about how you transmit > the information you would have, rather than how you process it. >=20 --=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/pj98vf%24n6o%241%40blaine.gmane.org. .