220 33552 article Path: news.gmane.org!.POSTED!not-for-mail From: Ville Voutilainen Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Catch block for multiple exceptions Date: Thu, 3 Aug 2017 02:37:58 +0300 Lines: 40 Approved: news@gmane.org Message-ID: References: <4126837.jZlGhgVnua@tjmaciei-mobl1> <54580edb-4a76-4241-b5c8-19ccbc1a562e@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" X-Trace: blaine.gmane.org 1501717086 3794 195.159.176.226 (2 Aug 2017 23:38:06 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 2 Aug 2017 23:38:06 +0000 (UTC) To: "ISO C++ Standard - Future Proposals" Original-X-From: std-proposals+bncBC5JHI7A7ALRBV6ERHGAKGQE5NYOIFI@isocpp.org Thu Aug 03 01:38:02 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf0-f199.google.com ([209.85.192.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dd3D9-0000ST-OS for gclcip-std-proposals@m.gmane.org; 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[2607:f8b0:400c:c08::242]) by mx.google.com with ESMTPS id p30si8415776uad.373.2017.08.02.16.37.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 02 Aug 2017 16:37:59 -0700 (PDT) Received-SPF: pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400c:c08::242 as permitted sender) client-ip=2607:f8b0:400c:c08::242; Original-Received: by mail-ua0-x242.google.com with SMTP id q25so3374963uah.0 for ; Wed, 02 Aug 2017 16:37:59 -0700 (PDT) X-Received: by 10.159.60.34 with SMTP id u34mr17468397uah.69.1501717079047; Wed, 02 Aug 2017 16:37:59 -0700 (PDT) Original-Received: by 10.103.103.65 with HTTP; Wed, 2 Aug 2017 16:37:58 -0700 (PDT) In-Reply-To: <54580edb-4a76-4241-b5c8-19ccbc1a562e@isocpp.org> X-Original-Sender: ville.voutilainen@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.b=vI4MZ2gh; spf=pass (google.com: domain of ville.voutilainen@gmail.com designates 2607:f8b0:400c:c08::242 as permitted sender) smtp.mailfrom=ville.voutilainen@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:33552 Archived-At: On 3 August 2017 at 01:56, Arthur O'Dwyer wrote: > FYI, this exact puzzle (variadic "catch") was discussed in the > #meta_programming Slack channel on June 30th; participants were Vittorio > Romeo, Barry Revzin, Eric Niebler, Peter Dimov, and myself (belatedly). My > solution is here. Its punch line is: > > try { > throw Derived(); // this is just a placeholder for some code > that might throw > } catch (...) { > variant_catch([](auto&& e) { > printf("caught %s (%s)\n", typeid(e).name(), > __PRETTY_FUNCTION__); > }); > } > > but with the caveat that this signature (also provided at the Wandbox link > above) will be more performant (not that we care about the performance of > the exceptional path, of course): > > variant_catch([&]() { > throw Derived(); // this is just a placeholder for some code that > might throw > }, [](auto&& e) { > printf("caught %s (%s)\n", typeid(e).name(), __PRETTY_FUNCTION__); > }); Note that both of our solutions suffer from the problem that the code in the catch-clause cannot break, continue, goto or return like plain code could. An if-else chain of any_casts from exception_ptr would be able to do that. -- 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/CAFk2RUZncz91iozp5d%3DWVhPCHwLa67dhmpwBRMEU5xioJvPuRA%40mail.gmail.com. .