220 35118 <1f284e0dd9faeabf60b45140e4c1a2b3@kdab.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Marc Mutz Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Marking more std::string_view members noexcept Date: Thu, 26 Oct 2017 19:44:04 +0200 Organization: KDAB Lines: 32 Approved: news@gmane.org Message-ID: <1f284e0dd9faeabf60b45140e4c1a2b3@kdab.com> References: <3d03cd7d-2177-98fd-408d-f74b1f6a8552@gmail.com> <3446274.dRsjijLxpX@tjmaciei-mobl1> <1931282.giciDSTxGt@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed X-Trace: blaine.gmane.org 1509039857 30040 195.159.176.226 (26 Oct 2017 17:44:17 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 26 Oct 2017 17:44:17 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCRPXDOU7ECRB3V5ZDHQKGQEH5LRBTI@isocpp.org Thu Oct 26 19:44:12 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wm0-f69.google.com ([74.125.82.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e7mCN-0006qm-Q0 for gclcip-std-proposals@m.gmane.org; Thu, 26 Oct 2017 19:44:07 +0200 Original-Received: by mail-wm0-f69.google.com with SMTP id z77sf2180794wmc.16 for ; Thu, 26 Oct 2017 10:44:15 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1509039855; cv=pass; d=google.com; s=arc-20160816; b=hHkvvCpJCMgQsqrg/D1L2v+14BLvnixY3mKUujtKBMuHwGCyj/RcbvzXiHaSAANR3X w/v9YvLKGNp2e5dhwIuSM9xno07fpb9+/2HgJzj/b+ge3QCpR1VOgtnuepCYEJSQLMTH dIAB4KvPPpx7rWQkiR/PUxPvY0Jzb3UU7GUC0qPwtSZNlVAjsev0pAC/CFpvm3AIl5Si Y+0AAnuLF3u6ZtqDyr92R5PJn2qAkatu8EaUhpN6109+pJoWxz82SFJO+Ba2huKlQqPf /Ig7xq4eaOsWnTB6U/emHnH/LSUrMeyhVI/mJFp2QbPURCPzSNVjNLWFQiOye07rA1i2 xreg== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-unsubscribe:list-subscribe:list-archive:list-help:list-post :list-id:mailing-list:precedence:reply-to:message-id:references :in-reply-to:organization:subject:to:from:date:mime-version :arc-authentication-results:arc-message-signature:dkim-signature :arc-authentication-results; bh=Fc/fsi5eafj5fp96SZVP5BzCO+XF+FB3gUay+1zkOso=; b=ZeSFwsOA/nCFZmeEnDvFmHhjxmSgwrdupv7LIO0v7jneUWpEuhE83cVnNZtwG7Vrlv Bvi6yelUfTT9cs2uoVZPTgc1fEeHi9kYmM+CaeEhIGbERmqzfEOLN0l8iZleKf7S8Mee MOveU4qpmz48OMAwdngnIxt1U1D7ADVluXKWpMyTuKDToSH3Vl90+2ElbeOkcZwlWaDt 9xlnZYIMVCvyulYx95ZzqoXJNnC4rRLqS4JPx/gm+YFqyzrJmhU4gw/zPoqprAayRPPG eHb2fhbpysSPgysx0YKzHDX+e9xtA1Yj1DYNK2fDB+pWVCjuSvJetBvMC2MZup9X84+V r90w== ARC-Authentication-Results: i=2; mx.google.com; spf=pass (google.com: domain of marc.mutz@kdab.com designates 176.9.126.58 as permitted sender) smtp.mailfrom=marc.mutz@kdab.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:date:from:to:subject:organization:in-reply-to :references:message-id:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=Fc/fsi5eafj5fp96SZVP5BzCO+XF+FB3gUay+1zkOso=; b=eYlEVavd4+1C12A/TepLg1bzkWOAKY3wct2fygYBxiIyvWMxxyKT1wIKNQr6NkVCkk bKp6JVEeG7XdcW4GniqMUxl1x8BWYZt1qBBxVvVcsXbhp7xBNzUVSGDaohtsFVREI5il 3Wpl2QHF97ebe/ZaoOYk4xWrJZDHZv1JUOGXa5nJ2JijbCRCyeeMl32HyipMcsT73QkS L7GEJ4QEP99OspphBprxVMpaavOpNT8vTVZSohWl3P/zmW3VmqqRls/ixC6EpEF8xky2 lse+AZRTpHhag5tS+siZh0b/48KvR4fU1yGO15NGFja4ndFnPSiUVnjiUEF0cOnBQowZ BAKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:date:from:to:subject:organization :in-reply-to:references:message-id:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=Fc/fsi5eafj5fp96SZVP5BzCO+XF+FB3gUay+1zkOso=; b=j5szdS5tc8TQhcmXa7oJLJE3eW/Giq470AKwuU/+EYCk8qfGUwsElxYQce4Pl9SmLm EpMTOSz/M1MaycixUVy6PhzBUji4bIIjbiQ7Hq/wAMLxyuXAm/dvotplQwEbQPf5YeBr p7HhnYw+VninYX2zMZGzRNRJc2kZgfAaGzFNQPojJzm6+BiR2LlIRa/2DuPqDiKJCUgJ fEg2rpzY+B+TH490H3xNQ3U2SwjLc9SrfHr8DYcOXNEcy69IxolW2g5LYhRLHs/V+Ist W7NcNCiOlqla3DQGWCtHxcMVUtzHmvvLL/4I05piGo4XNxcsOGG8MzF3eeNDPRz5Xpyy buFw== X-Gm-Message-State: AMCzsaUq5SldMYV660V2+aYxzZDgZl0qq3v6GusnO7DYuPev/dOxAsVu rBLwzd6HIwfB62h8B2Xpm+6POQ== X-Google-Smtp-Source: ABhQp+R2r/DDXC3l12yXeimuJOgj7MEx8i8bh658RD4Qp0ytk9NvsGxTAWfWBA/G+oDL3nKkZynwEA== X-Received: by 10.28.156.145 with SMTP id f139mr302490wme.10.1509039855250; Thu, 26 Oct 2017 10:44:15 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.191.29 with SMTP id p29ls28093wmf.8.canary-gmail; Thu, 26 Oct 2017 10:44:14 -0700 (PDT) X-Received: by 10.223.142.208 with SMTP id q74mr6686121wrb.172.1509039854133; Thu, 26 Oct 2017 10:44:14 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1509039854; cv=none; d=google.com; s=arc-20160816; b=d06HSPKGObOjRJN6RlQfh9PEDi8AUDl7P2yuUfJ4F7g6ZxoGr/4kR7jbv9RYX1duuY j7BkTCskKDePpXa47ZfUHasyPQTRz3Tof1oFDoZUgs8ewvHlJBrBpRyrlyo7wqIxp41r wWEAipGJ4KhpYUmthtfmI+V+207dRSAGM/HU7KUh/CyZwhCA02H+MA6015C4TisOYhGA 5Ucw22xD63//sbRF41ZG2/IkC0fOvLYexSMu4HnSP0EMWGbNuF3FeZGq/sDJXIZrC8Ku gnzGAhISUm5FLa8mbADShK5Fat9cEnEXHK3HZSDPfuW82tQ3H0ftVgtehHQeGvWdO4ra 8glQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:references:in-reply-to:organization:subject:to:from:date :content-transfer-encoding:mime-version:arc-authentication-results; bh=duJJtoqW/FNAibKdceD/BEuYnssj9hRkGh0fmjTraUY=; b=GCMNaexYPx/sF63hlZNUxmmdwUie2bI20rdyjQls84iZ4G1YOcRfd1t/N9vH97L+Wb SgQG/HjpnXIt+j/THKbY0pvj7+hJ9hWe2MYPy3TyThklXRLRpKpMnjhvZN5ogtpb1yUv K3PMDjwj7HjxjC22JYqTr1p3AdKiqXoHBS62s+nTqd1tqEsRV0g1rhwmg/CXSsWdx4eR x3uOA4j1N15/qyqsgwZoSGg1iDpQdKCnCKYvsWm4D3Y35Xex8FYtBnReZ1vHkAf6mwc3 w+dDlf4IjC6PX7mZXEmGTY/RcVBci0WwNsv6fE6RVEKXYn4MUboD4mDq+5zKPGTY0SZy quhA== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of marc.mutz@kdab.com designates 176.9.126.58 as permitted sender) smtp.mailfrom=marc.mutz@kdab.com Original-Received: from mail.kdab.com (mail.kdab.com. [176.9.126.58]) by mx.google.com with ESMTPS id o70si1331047wmd.69.2017.10.26.10.44.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 26 Oct 2017 10:44:14 -0700 (PDT) Received-SPF: pass (google.com: domain of marc.mutz@kdab.com designates 176.9.126.58 as permitted sender) client-ip=176.9.126.58; X-Virus-Scanned: amavisd-new at kdab.com In-Reply-To: <1931282.giciDSTxGt@tjmaciei-mobl1> X-Sender: marc.mutz@kdab.com X-Original-Sender: marc.mutz@kdab.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of marc.mutz@kdab.com designates 176.9.126.58 as permitted sender) smtp.mailfrom=marc.mutz@kdab.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:35118 Archived-At: On 2017-10-26 18:09, Thiago Macieira wrote: > On Thursday, 26 October 2017 01:55:04 PDT Marc Mutz wrote: >> > Calculating the length of char16_t* can't be done in a constexpr way. >> >> ... is only C++14-constexpr (well, if you want to support reasonably >> long strings, otherwise you could come up with a recursive >> implementation). > > No, it's not constexpr at all, since I can't run SSE or do > reinterpret_cast > from pointer to integer and back in constexpr mode. > > See http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/tools/ > qstring.cpp#n163 You'd think compilers would recognize an inlined strlen call and throw their own vectoriser at it, no? If not strlen, what else could they possibly auto-vectorise at all? :) And, yes, you can call such functions in constexpr functions: Just loop inline for, say, 64bytes and, if you haven't found the end by then, call the out-of-line hand-optimized function to do the rest. Thanks, Marc -- 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/1f284e0dd9faeabf60b45140e4c1a2b3%40kdab.com. .