From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff King Subject: Re: trim_common_tail bug? Date: Sun, 16 Dec 2007 02:06:14 -0500 Message-ID: <20071216070614.GA5072@sigill.intra.peff.net> References: <20071215111621.GA8139@coredump.intra.peff.net> <20071215155150.GA24810@coredump.intra.peff.net> <7vprx7n90t.fsf@gitster.siamese.dyndns.org> <20071215200202.GA3334@sigill.intra.peff.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Linus Torvalds , git@vger.kernel.org To: Junio C Hamano X-From: git-owner@vger.kernel.org Sun Dec 16 08:06:48 2007 Return-path: Envelope-to: gcvg-git-2@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1J3naI-0002lD-G6 for gcvg-git-2@gmane.org; Sun, 16 Dec 2007 08:06:46 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752478AbXLPHGT (ORCPT ); Sun, 16 Dec 2007 02:06:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752306AbXLPHGT (ORCPT ); Sun, 16 Dec 2007 02:06:19 -0500 Received: from 66-23-211-5.clients.speedfactory.net ([66.23.211.5]:3165 "EHLO peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752274AbXLPHGS (ORCPT ); Sun, 16 Dec 2007 02:06:18 -0500 Received: (qmail 20055 invoked by uid 111); 16 Dec 2007 07:06:16 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) (smtp-auth username relayok, mechanism cram-md5) by peff.net (qpsmtpd/0.32) with ESMTP; Sun, 16 Dec 2007 02:06:16 -0500 Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Sun, 16 Dec 2007 02:06:14 -0500 Content-Disposition: inline In-Reply-To: <20071215200202.GA3334@sigill.intra.peff.net> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Sat, Dec 15, 2007 at 03:02:02PM -0500, Jeff King wrote: > > for (i = 0, recovered = 0; recovered < trimmed && i <= ctx; i++) { > > while (recovered < trimmed && ap[recovered++] != '\n') > > ; /* nothing */ > > } > > > > then (warning: I haven't had my coffee yet)? > > Yes, I think that is equivalent. My sleep-deprived brain keeps thinking > there must be a more clear way of writing this whole loop, but it > escapes me at the moment. And this came to me in a dream. :) It fixes the bug, and I think it is a bit simpler to see the termination conditions in a single loop. But please double-check correctness, and that you agree that it is more readable. --- diff --git a/xdiff-interface.c b/xdiff-interface.c index 700def2..98b02ed 100644 --- a/xdiff-interface.c +++ b/xdiff-interface.c @@ -110,7 +110,7 @@ int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf) static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx) { const int blk = 1024; - long trimmed = 0, recovered = 0, i; + long trimmed = 0, recovered = 0; char *ap = a->ptr + a->size; char *bp = b->ptr + b->size; long smaller = (a->size < b->size) ? a->size : b->size; @@ -121,10 +121,9 @@ static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx) bp -= blk; } - for (i = 0, recovered = 0; recovered < trimmed && i <= ctx; i++) { - while (recovered < trimmed && ap[recovered] != '\n') - recovered++; - } + while (recovered < trimmed && ctx) + if (ap[recovered++] == '\n') + ctx--; a->size -= (trimmed - recovered); b->size -= (trimmed - recovered); }