220 28428 <0574ad73-0d36-47c0-9e47-79e234cc6708@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Edward Catmur Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Marking more std::string_view members noexcept Date: Tue, 27 Sep 2016 15:52:46 -0700 (PDT) Lines: 48 Approved: news@gmane.org Message-ID: <0574ad73-0d36-47c0-9e47-79e234cc6708@isocpp.org> References: <3d03cd7d-2177-98fd-408d-f74b1f6a8552@gmail.com> <2b8591ee-3a1e-4a41-8c14-221bdc5cd1e4@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2996_946260890.1475016766678" X-Trace: blaine.gmane.org 1475016778 24297 195.159.176.226 (27 Sep 2016 22:52:58 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 27 Sep 2016 22:52:58 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDZLZTXF7UJBBP7QVO7QKGQEPPDJCAQ@isocpp.org Wed Sep 28 00:52:54 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f69.google.com ([209.85.214.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bp1F1-00056y-GV for gclcip-std-proposals@m.gmane.org; Wed, 28 Sep 2016 00:52:47 +0200 Original-Received: by mail-it0-f69.google.com with SMTP id j69sf64961323itb.1 for ; Tue, 27 Sep 2016 15:52:49 -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 :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=/drpUSnhORY62UcfLe+I12y8GhyU9lCP88okTwEWKlQ=; b=UAQbiSFbolaIOHcL8HNn6IYcU+yiWO5ZykDdhIc/vSaiRktpnHqy4W4XI99hiR+vbb MLW45zpqYpP68TkHrzc30rEICYkct3/McOvTfgVGq8LvGoCBzWCGrAbaOqhkvu38Kyzj wkrRAHIqXgfzjpp4yVKPC/Bhm8RPFreoGb62qr2W5tOJ/ViGgoY+YM9SuuVTUxKacjYD bHdVx9S/rR2RUQICnV4lshyPc4q7YuULHIMPCZZN7wAunsm1UQeh26yf9BkqilzYaZ1+ oRhd99DjLLEPnIobX9xAaRIHscTzeWDxa7gEo1EK+rdio+XeeJsO3qRH1YM0mK4YSU/Q HaHw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; 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=/drpUSnhORY62UcfLe+I12y8GhyU9lCP88okTwEWKlQ=; b=kd+/eZdeqhOevtymQmE99DnwUHwpnHWlyNmHEdf1RCRcjmbuHyMMclJNZxS08GzYtv z1omwI0OXClDBKSJM4VBBpp5no35fJoNa5cPFs7tnuH5j+tduwgfzCEbkbrhIadKQ0V5 W1EleRP49DWbmsEWhGhTCcL3koozdwG/QpcSZoRXglbo8qRv1YjOG2wdbv8LnlvBBxa2 t2JLhdlW4Kvmod/K1WGrpcaUVEM2m4dqrGEeP1cxZX7SHVzC1ZYZrDWBeyCatHk6n0Uc KuNe45v8R+wrREb9+qdGXJPmEZ01U50dcZBYHGDN80TGTrBP1Dlt7hDVbir9ihDFfD6z HmEA== X-Gm-Message-State: AA6/9Rm8ajhlWjEJ+Yynagv/M0NYTM0heCGawuO2Hqp5yiSmv/im4Y1EpoxfRom+/k1+2Q== X-Received: by 10.36.242.129 with SMTP id j123mr1706456ith.36.1475016769077; Tue, 27 Sep 2016 15:52:49 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.106.72 with SMTP id l69ls1539784itc.16.gmail; Tue, 27 Sep 2016 15:52:47 -0700 (PDT) X-Received: by 10.36.217.2 with SMTP id p2mr384192itg.5.1475016767699; Tue, 27 Sep 2016 15:52:47 -0700 (PDT) In-Reply-To: X-Original-Sender: ed@catmur.co.uk 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:28428 Archived-At: ------=_Part_2996_946260890.1475016766678 Content-Type: text/plain; charset=UTF-8 On Tuesday, 27 September 2016 21:59:49 UTC+1, Andrey Semashev wrote: > On 09/27/16 23:42, Nicol Bolas wrote: > > > > On Tuesday, September 27, 2016 at 2:24:48 PM UTC-4, Andrey Semashev wrote: > > > > Still, it feels wrong that functions that you never expect to > > throw are not marked noexcept. When you write non-throwing code you > > would look at the functions your code calls and not seeing noexcept > > there immediately throws a red flag. > > > > I believe the point is that it /shouldn't/ "throw a red flag". This is a > > matter of simple practicality. > > > > C API functions cannot throw exceptions, but they equally are incapable > > of being marked `noexcept`. C++ libraries written before C++11 will not > > have non-throwing functions marked `noexcept`. And many C++ libraries > > even post-11 don't rigidly mark every non-throwing function as `noexcept`. > > > > At the end of the day, C++ programmers cannot in general assume that > > every function not marked `noexcept` is a throwing function. > > That is true. But if one really wants to rely on such function in a > non-throwing code, he would have to inspect its implementation or rely > on documentation stating it won't throw. C functions (i.e. the ones that > are declared extern "C") are not a problem in this respect as they > implicitly never throw. > > What I'm saying is that yes, you can use unmarked functions, but it > entails more cost on you and is more fragile (what if the function > starts to throw at some point in the future?) While by simply marking > the function you can remove that cost and make the no-throw guarantee > part of the interface. It is intentional that the function might start to throw in the future, or at least in certain compilation modes. A high quality implementation might well throw from front() called on an empty string_view when built in debug mode. noexcept is properly reserved for functions that have no preconditions, or where throwing would never be an appropriate reaction to precondition violation. -- 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/0574ad73-0d36-47c0-9e47-79e234cc6708%40isocpp.org. ------=_Part_2996_946260890.1475016766678-- .