From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: "Petros Travioli" Newsgroups: gmane.emacs.bugs Subject: bug#13949: fill-paragraph is buggy, but using MD5 is even more buggy Date: Mon, 28 Mar 2016 06:55:58 +0200 Message-ID: References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: ger.gmane.org 1459155082 20815 80.91.229.3 (28 Mar 2016 08:51:22 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 28 Mar 2016 08:51:22 +0000 (UTC) To: 13949@debbugs.gnu.org Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Mon Mar 28 10:51:11 2016 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1akStC-00086t-Tn for geb-bug-gnu-emacs@m.gmane.org; Mon, 28 Mar 2016 10:51:11 +0200 Original-Received: from localhost ([::1]:39735 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akStC-0004RT-5f for geb-bug-gnu-emacs@m.gmane.org; Mon, 28 Mar 2016 04:51:10 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:58357) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akSt7-0004O7-Aj for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 04:51:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1akSt4-00034H-4B for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 04:51:05 -0400 Original-Received: from debbugs.gnu.org ([208.118.235.43]:43630) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akSt4-00034D-15 for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 04:51:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1akSt3-0005OL-Q8 for bug-gnu-emacs@gnu.org; Mon, 28 Mar 2016 04:51:01 -0400 X-Loop: help-debbugs@gnu.org In-Reply-To: Resent-From: "Petros Travioli" Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Mon, 28 Mar 2016 08:51:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 13949 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 13949-submit@debbugs.gnu.org id=B13949.145915503420689 (code B ref 13949); Mon, 28 Mar 2016 08:51:01 +0000 Original-Received: (at 13949) by debbugs.gnu.org; 28 Mar 2016 08:50:34 +0000 Original-Received: from localhost ([127.0.0.1]:40757 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1akSsc-0005Nd-8e for submit@debbugs.gnu.org; Mon, 28 Mar 2016 04:50:34 -0400 Original-Received: from mout.gmx.net ([212.227.15.15]:64845) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1akPDh-0008JE-MO for 13949@debbugs.gnu.org; Mon, 28 Mar 2016 00:56:06 -0400 Original-Received: from [193.147.107.1] by 3capp-gmx-bs61.server.lan (via HTTP); Mon, 28 Mar 2016 06:55:58 +0200 Importance: normal Sensitivity: Normal X-Priority: 3 X-Provags-ID: V03:K0:37xiuKV9vqlgQZAsQB8MUlR4naMq6G/jpcHxEK0OrcC K/BsNwoh9Fn799hs/o4HrwSxm5DtGFmhrjIIoBCjq0VII7TkkL D/Lc+2WcUsCNoCkwYCFA1vAH3ar4175bgpMI5/MyfN2SaNFhqU WZQt+C/dkOPoQYVpUCsGRlKV2vbpdPw76PBNOHLwPqpzx/RrN+ zKPx09WM1qEFkxq4Qx2Etzjk0ImQP/K6qFY0qeM/8naD1YifRd tJz6i/5qLR88CSgieiE9JXiiyb0d+fMP6aMz8Xo0RfjFwPf3PK mJwC3I= X-UI-Out-Filterresults: notjunk:1;V01:K0:EZiZ5+0Gj3A=:9sXITP3wyFsWS4gZQxcy11 kUz9Ypni3bm88rz/OeTvnVhQ8Q1QUaQJ+H03q3kLOouWPwHqmVhTpTNorDQ218npADepkRnYI CDplBR6aJwFOGEYzqm2TrJ8HjlLtvat+KQcY9tig8umd0DQHU/mkGRVYncneuEh10RBmV5Nfh FXwszUoJYZaD5uPQ0sj6G/h79/KNLve8N71tNkqBMpI4+WGplQJE2MnG/Qe9KJEhN3HGpPOwZ uHQWI5HUCMjQnNYBifPCVZZs9ps/5N2WLDECRVo8Ae0sG4O36m/rdso0db6y27cIGNbav8xHb K+bsiXVCn84zwM5pZ8nodWNbguFvEtvAHTlPkd7K+bCteQmpN7cx+32xy5/UfB9/uYCexsdwI /DGugj2nFewBh+/ECoUGvdQUqRSBey/shDQ0G3suIGRDib9FpSnUMxo0UECY6wb/UwpDGLusf qLVvyuLFVg== X-Mailman-Approved-At: Mon, 28 Mar 2016 04:50:31 -0400 X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 208.118.235.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.bugs:115626 Archived-At: Some details on hashes. For eggheads. Let's assume that you have never typed in some large number, say, 89434823472. And you have never seen it so far. And noone you know has ever seen this number. Neither have your colleagues, though you don't speak to them. On this empirical basis, you declare this number nonexistant for all practical purposes. Encountering this number in the future is less likely than the probability of finding oneself with those two sweet blond ladies you've always wanted at your home in a horizontal position simultaneously. Since instead of the ladies, you have been accustomed to endure the society of your wife, well, you decide to use the value 89434823472 as an error value when, say, returning the file size. Is it clever? Of course NO. There is absolutely nothing which precludes the next large file you see to have size exactly 89434823472. There is absolutely nothing which precludes the next two large files you see to have this size. As the time goes by, files get larger, so 89 GB files may be normal in a decade or so. (The ladies will never change their mind, though. Sigh.) But that's exactly what happens when you are using hash functions to verify buffer equality, just with a more complicated mathematical formulation and at a slightly different scale. So don't use hash functions to a two-sided correct answer to test buffer equality. For a one-sided answer (if hash(x) != hash(y) then x != y), you are fine. Petros