Message-ID: <49739071.8030307@dazjorz.com>
Date: Sun, 18 Jan 2009 21:26:25 +0100
From: dazjorz <mailinglist AT dazjorz DOT com>
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To: cygwin AT cygwin DOT com
CC: Ed Schouten <ed AT 80386 DOT nl>
Subject: GNU coreutils does not work on Cygwin because of freopen() ?
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Hey all,

I'm not very great with the inner workings of GNU or Cygwin libc, so 
please bear with me if I make any mistakes or misunderstandings.

I was trying to get GNU coreutils to work on Cygwin. Maybe this seems 
weird to you guys, because Cygwin has coreutils, but there are a few 
reasons:
- Cygwin didn't have md5sum, GNU coreutils did (and I need md5sum)
- It should work, and "Because I Can" is always a valid reason in UNIX world
- I'm trying to bootstrap Debian on Cygwin, and coreutils from Debian is 
my first try; getting coreutils from Cygwin may be done later.

However, I noticed there are some very weird bugs happening. See for 
example, this bug in cat (don't look at the title of the page, I blamed 
bash first)
http://paster.dazjorz.com/?p=3845

A friend of mine and me have been trying to figure out what causes this. 
First, we tested if it wasn't a bug in open() + fork(). This seemed not 
to be the case. So we started looking further, and we're down to GNU 
`cat` calling freopen(). This is not POSIX-compliant and can cause 
problems like this.

`cat` and other coreutils tools only call freopen() if O_BINARY is 
defined on this platform. It's defined on Cygwin, because Cygwin makes a 
difference between O_TEXT and O_BINARY.

1. Why does Cygwin distinguish between O_TEXT and O_BINARY? Shouldn't 
this difference be removed from the Linux API side of Cygwin?
2. I don't know why coreutils is calling freopen() at all. Should I 
patch it out completely, or add something like an #ifndef __CYGWIN__ 
around the pieces of code in question?

I'm hesitant to patch coreutils, so I'm asking for your opinion first.

Thanks for any replies,
Sjors

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