From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22075 invoked by alias); 21 Apr 2014 18:46:46 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 21993 invoked by uid 89); 21 Apr 2014 18:46:46 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.7 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=3.3.2 X-HELO: mailbackend.panix.com Received: from mailbackend.panix.com (HELO mailbackend.panix.com) (166.84.1.89) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 21 Apr 2014 18:46:45 +0000 Received: from compute01.cs.columbia.edu (compute01.cs.columbia.edu [128.59.11.31]) by mailbackend.panix.com (Postfix) with ESMTP id C11D92E25A for ; Mon, 21 Apr 2014 14:46:43 -0400 (EDT) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Message-ID: <21333.26515.393838.380071@compute01.cs.columbia.edu> Date: Mon, 21 Apr 2014 18:46:00 -0000 To: cygwin@cygwin.com Subject: Re: fstat st_size on open files on Parallels filesystem is wrong In-Reply-To: <227151856.20140421223417@yandex.ru> References: <21333.25325.11106.958642@compute01.cs.columbia.edu> <227151856.20140421223417@yandex.ru> From: lennox@cs.columbia.edu X-SW-Source: 2014-04/txt/msg00491.txt.bz2 On Monday, April 21 2014, "Andrey Repin" wrote to "lennox at cs.columbia.edu, cygwin at cygwin.com" saying: > Greetings, lennox at cs.columbia.edu! >=20 > > I=E2=80=99m running cygwin64 1.7.29 in a Windows 8.1 Pro virtual machin= e, running in > > Parallels Desktop 9.0.24229 on Mac OS X 10.9.2. >=20 > > Parallels Desktop automatically mounts my Mac OS X home directory as a = Z: > > drive in Windows. Cygwin mount reports this drive as being type "prlsf= ". >=20 > > Unfortunately, I've discovered that if I have an open file on this > > filesystem which has been written to, the size returned by Cygwin fstat= () on > > the open file is wrong. A stat() of the file after it's been closed is > > correct. >=20 > > This has the consequence that emacs always thinks saved files have been > > modified externally, since emacs looks at files' sizes (as well as their > > modification times) to detect external changes. This makes emacs > > near-unusable. >=20 > > This problem does not occur for files in my Cygwin home directory, or o= ther > > locations mounted on my Windows C: drive. >=20 > > I've attached a simple unit test program that illustrates the problem. > > I've also attached my cygcheck -s -v -r output. >=20 > > Any ideas? Is this a Cygwin bug, a Parallels bug, or something else? > > Glancing over the Cygwin code, I see that there are a few cases where f= stat > > has special cases for certain filesystem types. >=20 > You never flushing the buffer in your test code, or I'm reading it wrong? This is using Posix APIs -- open() / write() -- not C APIs, fopen() / fwrite(), so there shouldn't be a buffer? Notice that the test behaves as I expect for a file on NTFS. Adding a call to fsync() prior to the fstat() call doesn't change anything. I've modeled this as closely as I could on what it appears emacs is doing, as far as I could tell. --=20 Jonathan Lennox lennox at cs.columbia.edu -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple