From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83]) by sourceware.org (Postfix) with ESMTPS id D915E389A101; Thu, 31 Mar 2022 16:01:24 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D915E389A101 X-IronPort-AV: E=Sophos;i="5.90,225,1643670000"; d="scan'208";a="29389192" Received: from pc94-85.math.u-psud.fr ([129.175.94.85]) by mail2-relais-roc.national.inria.fr with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Mar 2022 18:01:24 +0200 Date: Thu, 31 Mar 2022 18:01:23 +0200 (CEST) From: Marc Glisse Reply-To: libstdc++@gcc.gnu.org To: Matthias Kretz cc: gcc-patches@gcc.gnu.org, libstdc++@gcc.gnu.org Subject: Re: [PATCH] libstdc++: Implement std::unreachable() for C++23 (P0627R6) In-Reply-To: <3572914.e9J7NaK4W3@minbar> Message-ID: <48cc3e77-8f70-a4a7-ad16-22ba11d883b4@grove.saclay.inria.fr> References: <20220331153029.1898244-1-jwakely@redhat.com> <3572914.e9J7NaK4W3@minbar> MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset=US-ASCII X-Spam-Status: No, score=-3.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libstdc++@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++ mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 31 Mar 2022 16:01:26 -0000 On Thu, 31 Mar 2022, Matthias Kretz via Gcc-patches wrote: > I like it. But I'd like it even more if we could have > > #elif defined _UBSAN > __ubsan_invoke_ub("reached std::unreachable()"); > > But to my knowledge UBSAN has no hooks for the library like this (yet). -fsanitize=undefined already replaces __builtin_unreachable with its own thing, so I was indeed going to ask if the assertion / trap provide a better debugging experience compared to plain __builtin_unreachable, with the possibility to get a stack trace (UBSAN_OPTIONS=print_stacktrace=1), etc? Detecting if (the right subset of) ubsan is enabled sounds like a good idea. -- Marc Glisse