linux-kernel - Re: dup2() vs dup3() inconsistency when

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Date:	Fri, 10 Oct 2008 16:43:51 +0300
From:	Heikki Orsila <shdl@...alwe.fi>
To:	Ulrich Drepper <drepper@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, mtk.manpages@...il.com,
	Al Viro <viro@...iv.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: dup2() vs dup3() inconsistency when

On Thu, Oct 09, 2008 at 01:31:39PM -0700, Ulrich Drepper wrote:
> H. Peter Anvin wrote:
> > The dup2() behavior comes from the logical consequence of dup2()'s
> > "close on reuse"; one would think it would be logical for dup3() to
> > behave the same way.
> 
> No.  We deliberately decided on this change.  Otherwise, what is the
> result of dup3(fd, fd, O_CLOEXEC)?  There is no reason to use
> dup2(fd,fd), so why the hell somebody wants to defend this is beyond me.

The reason is: application programmers expect it to behave that way. 
The interface is mostly targeted for typical application programmers, 
and consistency decreases bugs. In this respect, it would be a good 
idea for dup3() to have the same semantics. Doing that might not make 
practical sense, but it is secondary to obviousness.

-- 
Heikki Orsila
heikki.orsila@....fi
http://www.iki.fi/shd
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