From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id E13823943401 for ; Thu, 31 Mar 2022 16:06:04 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E13823943401 Received: from mail-yw1-f199.google.com (mail-yw1-f199.google.com [209.85.128.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-656-ATE5wD13PU6ChA1yVFAUIQ-1; Thu, 31 Mar 2022 12:06:00 -0400 X-MC-Unique: ATE5wD13PU6ChA1yVFAUIQ-1 Received: by mail-yw1-f199.google.com with SMTP id 00721157ae682-2d7eaa730d9so2066297b3.13 for ; Thu, 31 Mar 2022 09:06:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Pi2g4jqqFzWhzEtQAe0sEHO+zA8i79NjlJlBg4DGpLM=; b=XnfY7Rx6lJpB+CflunCeP9ChAXQgQlIZNBd/+8eiUAtjogXRgujLRqY35uIzhpYhDb 5yC4KvZjyVYPHM61Hk0ALp/9WRL5IP012pZZfXZyNwrDprksrO2Ou4lGpHgDDSXoJQmp uvKC8LdLEhsf9Ak2LnWds8F1cp2eXTIEaHBR2z8G5wTLJszZeEsj+jUIkO+oql8j+Xnt ywIZvGJLifosW9+x/E9HWZ3LQ7ebHatCVYuEoDTYm7RxgO1tqFsB6wixBmBv6kNkCKGV JP6CNyzLCYJcgF9cqRZm9IXsUvlWioDBSZ5/hhyOYXXOKyLwvEORStgkmJnkpZwFhaGT tDdA== X-Gm-Message-State: AOAM530nSINz2SiwFRfy1ePyxkQpx4Pwv6ydZCRWBMTjjfs2Plmc1iTh P7vK6X/OTAaUMvSsMF/Q5ljFFW/oqx0ymjUACuM774V94AUODyvcJWlt8Tx+hD3kKzUF0tQ/AwE 9y1MD7nETgta+nfTBMwMmLY7YeXy0OoE0mg== X-Received: by 2002:a81:6e54:0:b0:2e5:caaf:e1a1 with SMTP id j81-20020a816e54000000b002e5caafe1a1mr5381946ywc.475.1648742759960; Thu, 31 Mar 2022 09:05:59 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx85jGqtK1dYx2bkALNcMCGfOe/xlIjFz9VQHr9Sg2FUvDn+CB1r09xKXRFlKEMvlRMc+suMpK47SV5KYj0fGk= X-Received: by 2002:a81:6e54:0:b0:2e5:caaf:e1a1 with SMTP id j81-20020a816e54000000b002e5caafe1a1mr5381929ywc.475.1648742759797; Thu, 31 Mar 2022 09:05:59 -0700 (PDT) MIME-Version: 1.0 References: <20220331153029.1898244-1-jwakely@redhat.com> <3572914.e9J7NaK4W3@minbar> <48cc3e77-8f70-a4a7-ad16-22ba11d883b4@grove.saclay.inria.fr> In-Reply-To: <48cc3e77-8f70-a4a7-ad16-22ba11d883b4@grove.saclay.inria.fr> From: Jonathan Wakely Date: Thu, 31 Mar 2022 17:05:48 +0100 Message-ID: Subject: Re: [PATCH] libstdc++: Implement std::unreachable() for C++23 (P0627R6) To: "libstdc++" Cc: Matthias Kretz , Marc Glisse , gcc Patches X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 31 Mar 2022 16:06:06 -0000 On Thu, 31 Mar 2022 at 17:03, Marc Glisse via Libstdc++ wrote: > > 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. Does UBsan define a macro that we can use to detect it?