From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: [Emacs-diffs] master 605f901: Prefer memcpy and memset to doing it by hand Date: Sun, 7 Feb 2016 13:24:28 -0800 Organization: UCLA Computer Science Department Message-ID: <56B7B60C.7070407@cs.ucla.edu> References: <20160205003917.14369.86929@vcs.savannah.gnu.org> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1454880298 11643 80.91.229.3 (7 Feb 2016 21:24:58 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 7 Feb 2016 21:24:58 +0000 (UTC) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Feb 07 22:24:50 2016 Return-path: Envelope-to: ged-emacs-devel@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 1aSWp8-0000vP-N0 for ged-emacs-devel@m.gmane.org; Sun, 07 Feb 2016 22:24:50 +0100 Original-Received: from localhost ([::1]:38395 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aSWp7-0003gj-W0 for ged-emacs-devel@m.gmane.org; Sun, 07 Feb 2016 16:24:49 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:33008) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aSWou-0003gd-Jw for emacs-devel@gnu.org; Sun, 07 Feb 2016 16:24:37 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aSWor-0002kK-Eg for emacs-devel@gnu.org; Sun, 07 Feb 2016 16:24:36 -0500 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:53804) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aSWor-0002jb-8l for emacs-devel@gnu.org; Sun, 07 Feb 2016 16:24:33 -0500 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id F3BDC160E48 for ; Sun, 7 Feb 2016 13:24:29 -0800 (PST) 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 QRi_GYN4CUKE for ; Sun, 7 Feb 2016 13:24:29 -0800 (PST) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 53E11160F5C for ; Sun, 7 Feb 2016 13:24:29 -0800 (PST) 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 K0C3mqF56Hx2 for ; Sun, 7 Feb 2016 13:24:29 -0800 (PST) Original-Received: from [192.168.1.9] (pool-100-32-155-148.lsanca.fios.verizon.net [100.32.155.148]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 2F9E5160E48 for ; Sun, 7 Feb 2016 13:24:29 -0800 (PST) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 In-Reply-To: X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 131.179.128.68 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 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-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:199463 Archived-At: John Wiegley wrote: > Is this so performance critical that we can't just always use the memset? We can't always use the memset. The memset works only if the bit pattern we're trying to store can be implemented by storing the same unsigned char value repeatedly. The important special case here is storing Qnil, which is represented by the all-zeros bit pattern.