220 39325 article Path: news.gmane.org!.POSTED!not-for-mail From: Jake Arkinstall Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Alternative proposal for mapping P0709 Deterministic Exceptions into C Date: Tue, 24 Jul 2018 02:54:59 +0100 Lines: 72 Approved: news@gmane.org Message-ID: References: <6a65c934-5d2a-4e75-b88d-9eaaee338bd3@isocpp.org> <1c229827-6d5d-45bd-8766-c3af818b2b0b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="0000000000004130860571b50d36" X-Trace: blaine.gmane.org 1532397184 1796 195.159.176.226 (24 Jul 2018 01:53:04 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 24 Jul 2018 01:53:04 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDCZX3WUUQFRB7MN3LNAKGQEE5EMIBY@isocpp.org Tue Jul 24 03:53:00 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-io0-f199.google.com ([209.85.223.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fhmVY-0000LN-DK for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id d1-v6sor166090itf.5.2018.07.23.18.55.09 for (Google Transport Security); Mon, 23 Jul 2018 18:55:09 -0700 (PDT) Received-SPF: pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a24:2206:: with SMTP id o6-v6mr1151167ito.112.1532397308946; Mon, 23 Jul 2018 18:55:08 -0700 (PDT) In-Reply-To: <1c229827-6d5d-45bd-8766-c3af818b2b0b@isocpp.org> X-Original-Sender: jake.arkinstall@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=JgohdTEM; spf=pass (google.com: domain of jake.arkinstall@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jake.arkinstall@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:39325 Archived-At: --0000000000004130860571b50d36 Content-Type: text/plain; charset="UTF-8" Error handling via an effective static state isn't thread safe. Marking the flag as volatile and telling users to check for errors immediately after the function call goes some way to help, I guess, but it's not sufficient to guarantee that errors won't crop up in the wrong thread (or do I have some reading to do?) This issue is conceded in the paper, albeit referenced as "complicated function calls", but later they state that the C standard library should make this ubiquitous. It follows that any code using this approach in future (and any code that calls that code, and so on) is not thread safe. Any error which occurs in one thread could pop up as an error in a different thread - and depending how deep that error handling code is in a library, this could have a devastating impact. An option is to have the error structs as an array indexed by thrd_current(). This means dynamic allocation and the introduction of helper functions rather than the nice direct struct member access, and thus it is unlikely to gain much traction. -- 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/CAC%2B0CCP_jeR%3Dfr7a%2BXVeVJ%2B0wm4KG9U6iEunOHk3y2qSi3jrjg%40mail.gmail.com. --0000000000004130860571b50d36 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Error ha= ndling via an effective static state isn't thread safe. Marking the fla= g as volatile and telling users to check for errors immediately after the f= unction call goes some way to help, I guess, but it's not sufficient to= guarantee that errors won't crop up in the wrong thread (or do I have = some reading to do?)

This issue is conceded in the paper,=C2=A0albeit referenced as &q= uot;complicated function calls", but later they state that the C stand= ard library should make this ubiquitous.

<= div dir=3D"auto">It follows that any code using this approach in future (an= d any code that calls that code, and so on) is not thread safe. Any error w= hich occurs in one thread could pop up as an error in a different thread - = and depending how deep that error handling code is in a library, this could= have a devastating impact.

An option is to have the error structs as an array indexed by thrd_curr= ent(). This means dynamic allocation and the introduction of helper functio= ns rather than the nice direct struct member access, and thus it is unlikel= y to gain much traction.

--
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To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAC%2B0CC= P_jeR%3Dfr7a%2BXVeVJ%2B0wm4KG9U6iEunOHk3y2qSi3jrjg%40mail.gmail.com. --0000000000004130860571b50d36-- .