220 31237 article Path: news.gmane.org!.POSTED!not-for-mail From: Oliver Kowalke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: P0534: call/cc, type safety and exceptions Date: Wed, 1 Mar 2017 11:59:02 +0100 Lines: 158 Approved: news@gmane.org Message-ID: References: <3a57e294-7254-4358-828d-c9f7757f5295@isocpp.org> <9deccbda-26ca-4ad8-a579-1feb674676a6@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a11c03ed8835fdd0549a9344e X-Trace: blaine.gmane.org 1488365964 1920 195.159.176.226 (1 Mar 2017 10:59:24 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 1 Mar 2017 10:59:24 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCLZHP5J7MHRBC6T3LCQKGQE7OGWEIY@isocpp.org Wed Mar 01 11:59:19 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qk0-f198.google.com ([209.85.220.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cj1yY-0008VA-Fg for gclcip-std-proposals@m.gmane.org; Wed, 01 Mar 2017 11:59:18 +0100 Original-Received: by mail-qk0-f198.google.com with SMTP id u188sf55040446qkc.1 for ; Wed, 01 Mar 2017 02:59:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=8cqCQZQOckfnckhZNZX7lnG40TvZ42uJf7szi7S8qX4=; b=B4IpAyyYoP3GHXzsK7/I03GIcFdQBlrC8S4c1utlz9vjwfWQQzw8gRGMO07EmW2M3b dx/QbNrHRthTaKg/CGejhcn7xAJLZppIt56yVghNE7g0D/Rz1b+xUmoeZ9wnr4CvAOGK m5PPaRp0R+9llCgjbSNORkFF8Of3yTJQVjwr6N9qgeocmP+v9Zhw43gLZQjzIg/4SUSa 55r1gHuo876CDSzZR5IVZWBsjSKj32lTOLlzwhcuvcAeoLmP7hVSLiYnx5Gt4onHJ/kS m/HMi/l9mVY+y6LFJZ4aOtDFhNyPMFPNbvAZ0iYnEco5gOjpyEpCIx3q/TP83Ebk5jI8 FVCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=8cqCQZQOckfnckhZNZX7lnG40TvZ42uJf7szi7S8qX4=; b=ujhfSwhWuV0MSjM3JdMVJ5HoxIlPdDVsQMouwVBWulkKI/RjBh6Gahdcs69dnqGDyc 2ZN3EXPBlPVc64je/XMptNTu0vmrDiR16WtizxsQzajgW617f3l/Tiw2bjGR8VDTUCoY 2VhpS+PixrP+rJBc4nNzGHhNtMHs7jl7fb27eZxJiwcJcH9YgdNI28Qcj9Dqn7zYSz8Y wtMJYXLVgOcZFNitI/pNeyTduAWO6mOfdG9qS0PyyonGTvC8o18kvkBMzm/eMQcBOLaL EokK6RPtOrLASiNQwxrbadzz0mY9TR4QifqefC9iEC+YOnKVEkEiyMINv33HTHegv/lA K5pw== X-Gm-Message-State: AMke39luqvwQ2LJpYfJVDqYuwGgDmFfZc7zbBRZYzL6aOlc6V+hy/IblK2Xr2ibUNIpH2g== X-Received: by 10.237.60.99 with SMTP id u32mr2217730qte.24.1488365964355; Wed, 01 Mar 2017 02:59:24 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.7.195 with SMTP id 61ls3580969oto.31.gmail; Wed, 01 Mar 2017 02:59:23 -0800 (PST) X-Received: by 10.129.4.68 with SMTP id 65mr2807958ywe.333.1488365963382; Wed, 01 Mar 2017 02:59:23 -0800 (PST) Original-Received: from mail-yw0-x22d.google.com (mail-yw0-x22d.google.com. [2607:f8b0:4002:c05::22d]) by mx.google.com with ESMTPS id v15si497801ywv.13.2017.03.01.02.59.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Mar 2017 02:59:23 -0800 (PST) Received-SPF: pass (google.com: domain of oliver.kowalke@gmail.com designates 2607:f8b0:4002:c05::22d as permitted sender) client-ip=2607:f8b0:4002:c05::22d; Original-Received: by mail-yw0-x22d.google.com with SMTP id d1so28517080ywd.2 for ; Wed, 01 Mar 2017 02:59:23 -0800 (PST) X-Received: by 10.37.11.146 with SMTP id 140mr2767816ybl.35.1488365962876; Wed, 01 Mar 2017 02:59:22 -0800 (PST) Original-Received: by 10.129.173.21 with HTTP; Wed, 1 Mar 2017 02:59:02 -0800 (PST) In-Reply-To: <9deccbda-26ca-4ad8-a579-1feb674676a6@isocpp.org> X-Original-Sender: oliver.kowalke@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of oliver.kowalke@gmail.com designates 2607:f8b0:4002:c05::22d as permitted sender) smtp.mailfrom=oliver.kowalke@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: 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:31237 Archived-At: --001a11c03ed8835fdd0549a9344e Content-Type: text/plain; charset=UTF-8 2017-03-01 11:39 GMT+01:00 : > 2) P0534 is intended to be as low level as possible while still being >> functional. By specializing types, it would be higher level than strictly >> *necessary*. >> > > low level API it's fcontext_t and several functions to context switching, > continuation it's high level wrapper > that's wrong > On Wednesday, March 1, 2017 at 10:26:57 AM UTC+3, Oliver Kowalke wrote: >> >> For instance during the implementation of my coroutine and fiber >> libraries I encountered that initialization- and termination-phases were >> required. In those phases no data at all or data of different types are >> transferred. >> Imagine the type of the transferred data does not have an default-ctor - >> you have to pass an value each time the continuation is resumed. What if >> you can't produce one or you want to terminate the continuation. >> Of course you could use something like variant or optional, but you would >> pay each time for the overhead even in cases were you don't need >> variant/optional etc. >> > also you can use custom type for wrap it and reduce overhead, or hide > internals from use > you still pay for thinks you don't need The switch mechanism proposed in P0534 is symmetric, e.g you have to >> explicitly specify the continuation that has to resumed next. >> To which continuation do you want to jump to in context_exit? >> > If I get you right `context_exit` executed ontop of caller context > because in `context_entry` we have: > ontop_fcontext( t.fctx, rec, context_exit< Rec >); > and if we catch exception in continuation, we can rethrow it to caller > context in context_exit > or I don't understand some use cases? > if you throw an exception in the middle of your continuation and it it escapes the top-level continuation you have no guaranttee that the calling continuation is still valid (might resumed and termianted already) -- 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/CA%2Bwfc19hFNcyjVn%3DoiFn%2Brf%3DzUYYyxjmZ-Zp-wDiK2n61DqeaA%40mail.gmail.com. --001a11c03ed8835fdd0549a9344e Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
2017= -03-01 11:39 GMT+01:00 <ogee@agnicore.com>:
2) P0534 is intended to be as low level as po= ssible while still being functional. By specializing types, it would be hig= her level than strictly necessary.
low level API it's fcontext_t and = several functions to context switching, continuation it's high level wr= apper

that's wrong
<= /div>
=C2=A0
On = Wednesday, March 1, 2017 at 10:26:57 AM UTC+3, Oliver Kowalke wrote:
For instance during the implementation of my corouti= ne and fiber libraries I encountered that initialization- and=20 termination-phases were required. In those phases no data at all or data of different types are transferred.
Imagine the type of the transf= erred data does not have an default-ctor - you have to pass an value each time the continuation is resumed. What if you can't produce one or you want to terminate the continuation.
Of course you could use something like variant or optional, but you would=20 pay each time for the overhead even in cases were you don't need=20 variant/optional etc.
also = you can use custom type for wrap it and reduce overhead, or hide internals = from use

you still pa= y for thinks you don't need


The switch mechanism proposed in P0534 is symmetric, e.g you have to=20 explicitly specify the continuation that has to resumed next.
To which continuation do you want to jump to in context_exit?
If I get you right `context_exit` executed ontop of ca= ller context because in `context_entry` we have:
ontop_fcontext( t.fctx, rec, context_exit< Rec >);
and if we catch exceptio= n in continuation, we can rethrow it to caller context in context_exit
o= r I don't understand some use cases?
=
if you throw an exception in the middle of your continuation and = it it escapes the top-level continuation you have no guaranttee that the ca= lling continuation is still valid (might resumed and termianted already)

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