From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/15029 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Jeffrey Walton Newsgroups: gmane.linux.lib.musl.general Subject: Re: max_align_t mess on i386 Date: Sun, 15 Dec 2019 16:51:27 -0500 Message-ID: References: <20191214151932.GW1666@brightrain.aerifal.cx> <20191215182314.GB986899@wirbelwind.zhasha.com> <20191215185125.GB1666@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="145277"; mail-complaints-to="usenet@blaine.gmane.org" To: musl@lists.openwall.com Original-X-From: musl-return-15045-gllmg-musl=m.gmane.org@lists.openwall.com Sun Dec 15 22:52:00 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1igbnt-000bWz-UY for gllmg-musl@m.gmane.org; Sun, 15 Dec 2019 22:51:54 +0100 Original-Received: (qmail 21684 invoked by uid 550); 15 Dec 2019 21:51:51 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 21663 invoked from network); 15 Dec 2019 21:51:50 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:reply-to:from:date:message-id :subject:to; bh=Iqom/eO3mf7UHb7EG+ZmHHJSTg8yfeVKNPwKjr9oeU8=; b=JKrNRUDtvWoRVdbR9A6zL+W+c2Jn/xhp1bHqcDkMc0U9Kl7PuR7l/xvGLE6knuH1LK 6fig3EwMwxdxAO//12QYRMHic7+paORG1OSMO6bvt6qdSaY4cBv+kN/g+uOgJNdTz3hb ya9jDL/pPlIvgfmc3/jibwuR8C4itbJrQTQJihvwgysIKt/OFTHgmcPk9adYsr+ulau3 jeUYuke8ap753t0dGPi/h3XcjjBTrtqJqNAL5KLb3GZZ7FYD1hSSMv0/bFzKPH48NKjZ 0WVy9tbWvfP3tpIhHrt++dXarVAMWG7yGiWNoae8dR9ELvYiqzpnBWXY7hsLEp7dpL8y JwPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:reply-to :from:date:message-id:subject:to; bh=Iqom/eO3mf7UHb7EG+ZmHHJSTg8yfeVKNPwKjr9oeU8=; b=FWS099qKqDaO/WuJKKsA4wsF01J802P0pizQGdklBNtR8nF3q9GQB1s6QdSUhTXIgC cgA+WHMg5sKx/oIackFr3O6mAY+fb/FNj+ArJmYRHBnIGmE0O4KgEkClV7yb3derh2Bc pVbP2glT12g+byd3oY5ezUGM68eLPqqLP4Zu4+N7Oc3JcCVTPh8K+W8SHDK6ywB/1RgF /ZNyRzm/TJPycEYsclDbz7zzbJL7KZ2zk6hNn9SuTz43NAa74ErzbCMpt0EV1OZ27U9q hzG9KphpuXih/z+86rm06VfoWrpGHadoy0gyMwX3idLuqSHYQbv16CG4xjxdOuZ8fkfX SAbQ== X-Gm-Message-State: APjAAAWEigI8scR6TEaEuQjFNhfEjjxmkqbJ1SWe9+46ljyVUCssqJyF VQIZRqLOHc11BwUahABdv9FPajfhWn3QfnzwaE4t5MpD X-Google-Smtp-Source: APXvYqyAnfWNMiWV8bAsrSjLCqm7V4OGI6W8xnlq8eAz0/XA2InV9aRJx7rfNWxL2jVaozxVNBUvr85gNr03GMvEdPU= X-Received: by 2002:a5d:9c4e:: with SMTP id 14mr16326697iof.166.1576446698417; Sun, 15 Dec 2019 13:51:38 -0800 (PST) In-Reply-To: Xref: news.gmane.org gmane.linux.lib.musl.general:15029 Archived-At: On Sun, Dec 15, 2019 at 3:03 PM Alexander Monakov wrote: > > ... > [SNIP] Which makes those bit positions available for flags > associated with the pointer, if you can arrange for them to be masked off > to use the pointer itself. Be careful of those tricks. I believe they are called Tagged Pointers. Aarch64 was doing it for a while. It caused a lot of problems in practice. It was breaking diagnostic tools. It was also holding up the porting of some libraries. See, for example, https://releases.llvm.org/6.0.0/tools/clang/docs/HardwareAssistedAddressSanitizerDesign.html and https://bugzilla.mozilla.org/show_bug.cgi?id=1143022 . Jeff