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From: ericblake AT comcast DOT net
To: Lieven Govaerts <lieven DOT govaerts AT gmail DOT com>
Cc: cygwin AT cygwin DOT com
Subject: Re: pwd output changed with coreutils upgrade from 5.2.1-4 to 5.3.0-2
Date: Tue, 22 Feb 2005 23:41:34 +0000
Message-Id: <022220052341.28716.421BC32D000DA54F0000702C22007507440A050E040D0C079D0A@comcast.net>
X-Authenticated-Sender: ZXJpY2JsYWtlQGNvbWNhc3QubmV0

> Hi all, 
> 
> I'm using the pwd.exe command from a standard winXP command prompt
> ( for building Mozilla ). 
> 
> However, when I upgrade to coreutils 5.3.0-2 I get this weird result:
> C:\devel\lgo\mozilla>pwd
> pwd: reading directory `../../../..'
> 
> Even more strange, is that when I execute pwd from the command prompt, I hear 
> my floppy disk being accessed. 
> 
> Can somebody help me out on this? Is this expected behaviour?
> 

I can reproduce the bug.  It is because coreutils switched in 5.3.0 to using opendir("..")/readdir()/closedir() to find the child directory in .. with the same inode as stat(".").  However, using the readdir() sequence on "/cygdrive":
 a) scans all Windows drives, including floppies (hence the sound of your disk access)
 b) tickles a cygwin bug where closedir() incorrectly returns -1 without setting errno (hence the cryptic error message from pwd)

The bug never bit me in testing because I tested from mount points other than /cygdrive.

Also, there is a known bug in coreutils, http://lists.gnu.org/archive/html/bug-coreutils/2005-02/msg00085.html, that pwd(1) is not POSIX compliant because it does not have a -L option that defaults to reading $PWD rather than assuming -P and scanning inodes.

Until such time as a cygwin snapshot fixes closedir() to work correctly (hopefully by cygwin 1.5.13), or such time as I release a coreutils with a compiled in hack to ignore the return of closedir if errno is unchanged, you have two workarounds:
 a) rather than using /bin/pwd, use the builtin pwd of /bin/sh or /bin/bash
 b) use mount(1) to ensure that your files can be accessed without having to use /cygdrive as their prefix

--
Eric Blake




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