From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: integer overflow handling for most-negative-fixnum Date: Mon, 23 Jul 2018 12:40:36 -0700 Organization: UCLA Computer Science Department Message-ID: References: <867elsq78b.fsf@gmail.com> <866018yl76.fsf@gmail.com> <83a7qkzyhz.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1532374756 12987 195.159.176.226 (23 Jul 2018 19:39:16 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 23 Jul 2018 19:39:16 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 To: Helmut Eller , emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Jul 23 21:39:12 2018 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fhgfo-0003EY-85 for ged-emacs-devel@m.gmane.org; Mon, 23 Jul 2018 21:39:12 +0200 Original-Received: from localhost ([::1]:36199 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fhght-0008KO-Az for ged-emacs-devel@m.gmane.org; Mon, 23 Jul 2018 15:41:21 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:57075) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fhghG-0008KJ-Lk for emacs-devel@gnu.org; Mon, 23 Jul 2018 15:40:44 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fhghD-0005XR-IU for emacs-devel@gnu.org; Mon, 23 Jul 2018 15:40:42 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:56662) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fhghD-0005X6-8r for emacs-devel@gnu.org; Mon, 23 Jul 2018 15:40:39 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 064FF160DFC; Mon, 23 Jul 2018 12:40:38 -0700 (PDT) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id nuTagpXAmPhQ; Mon, 23 Jul 2018 12:40:37 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 30C93160DFD; Mon, 23 Jul 2018 12:40:37 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id CS79xBAMd_-u; Mon, 23 Jul 2018 12:40:37 -0700 (PDT) Original-Received: from [192.168.1.9] (unknown [47.154.30.119]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id E114C160DFC; Mon, 23 Jul 2018 12:40:36 -0700 (PDT) Openpgp: preference=signencrypt Autocrypt: addr=eggert@cs.ucla.edu; prefer-encrypt=mutual; keydata= xsFNBEyAcmQBEADAAyH2xoTu7ppG5D3a8FMZEon74dCvc4+q1XA2J2tBy2pwaTqfhpxxdGA9 Jj50UJ3PD4bSUEgN8tLZ0san47l5XTAFLi2456ciSl5m8sKaHlGdt9XmAAtmXqeZVIYX/UFS 96fDzf4xhEmm/y7LbYEPQdUdxu47xA5KhTYp5bltF3WYDz1Ygd7gx07Auwp7iw7eNvnoDTAl KAl8KYDZzbDNCQGEbpY3efZIvPdeI+FWQN4W+kghy+P6au6PrIIhYraeua7XDdb2LS1en3Ss mE3QjqfRqI/A2ue8JMwsvXe/WK38Ezs6x74iTaqI3AFH6ilAhDqpMnd/msSESNFt76DiO1ZK QMr9amVPknjfPmJISqdhgB1DlEdw34sROf6V8mZw0xfqT6PKE46LcFefzs0kbg4GORf8vjG2 Sf1tk5eU8MBiyN/bZ03bKNjNYMpODDQQwuP84kYLkX2wBxxMAhBxwbDVZudzxDZJ1C2VXujC OJVxq2kljBM9ETYuUGqd75AW2LXrLw6+MuIsHFAYAgRr7+KcwDgBAfwhPBYX34nSSiHlmLC+ KaHLeCLF5ZI2vKm3HEeCTtlOg7xZEONgwzL+fdKo+D6SoC8RRxJKs8a3sVfI4t6CnrQzvJbB n6gxdgCu5i29J1QCYrCYvql2UyFPAK+do99/1jOXT4m2836j1wARAQABzSBQYXVsIEVnZ2Vy dCA8ZWdnZXJ0QGNzLnVjbGEuZWR1PsLBfgQTAQIAKAUCTIByZAIbAwUJEswDAAYLCQgHAwIG FQgCCQoLBBYCAwECH In-Reply-To: Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 131.179.128.68 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:227742 Archived-At: Helmut Eller wrote: > Can't you simply use some other character for this, like %z (or %=E2=84= =A4) and > leave %x alone. It'd require three new letters, since %o is also affected. I'd rather not= chew=20 up so many letters for such an obscure feature. And as it doesn't appear = that=20 this change will break much if anything, I'd rather not chew up any lette= rs at=20 all; let's just fix %x etc. so that they're not machine-dependent. >> However, it would >> be an incompatible change, so let's have the behavior depend on a >> compatibility variable, much as we already do for >> read-integer-overflow-as-float. >=20 > This sounds more like that other desaster: text-quoting-style. :-) Yes, I remember that well. However, this is a much smaller deal. With= =20 text-quoting style I had to change many uses and the magnitude of the tas= k was=20 known (most of it was in the patches I proposed). Here, I've audited the = Emacs=20 source code and have not found any need to change anything, except option= ally=20 for appearance to make a few strings look nicer, and in a couple of tests= that=20 stress Emacs with unlikely inputs, tests that I've updated in the patch I= =20 proposed. See Bug#32252. > %a also seems like a candidate: in C99 %a prints floating point numbers > in hexadecimal notation. If we were to implement %a it should be reasonably consistent with C99 %a= , and=20 this is something quite different from %x and %X and %o. So we should use= a=20 different letter, if we're going to use any new letter which I'd rather n= ot. > That might be useful so that Emacs can write/read floats without roundi= ng errors. We already have that: (format "%s" N) outputs any number N in a format th= at can=20 be read back without rounding errors. Similar functionality is available = via=20 (number-to-string N), (prin1-to-string N), etc. With all these, the only = loss of=20 floating-point info is with NaNs, something I'd like to fix even though t= hey're=20 not numbers.