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Re: dup2 on mingw

From: Eric Blake
Subject: Re: dup2 on mingw
Date: Tue, 21 Jul 2009 13:50:59 +0000 (UTC)
User-agent: Loom/3.14 (http://gmane.org/)

Eric Blake <ebb9 <at> byu.net> writes:

> > Yes, that's definitely a portability pitfall that warrants a wrapper module.
> And in writing the testcase, I learned that cygwin 1.5 also has a bug, in
> that dup2(1,1) returns 0 (but at least cygwin's dup2(1,2) returns 2).
> Although you seldom see code using dup2 as a no-op for an fd onto itself,
> it provides a great way to non-destructively check whether an fd is open
> without having to use fcntl or _get_osfhandle (and so I did just that in
> test-pipe.c).

Well, it would be nice if doing that didn't hang mingw.  It looks like 
Microsoft has a bug, because using dup2(fd,fd) when fd is closed appears to 
deadlock the process.

I also botched the interaction between fchdir and dup2 (they can't both define 

I'm working on a followup patch for both of these issues.

Eric Blake

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