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

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Date:	Fri, 10 Oct 2008 15:02:44 +0200
From:	Bernd Petrovitsch <bernd@...mix.at>
To:	mtk.manpages@...il.com
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: dup2() vs dup3() inconsistency when

On Fri, 2008-10-10 at 14:15 +0200, Michael Kerrisk wrote:
> On Fri, Oct 10, 2008 at 2:09 PM, Bernd Petrovitsch <bernd@...mix.at> wrote:
> > On Fri, 2008-10-10 at 07:04 +0200, Michael Kerrisk wrote:
> > [....]
> >> Well, as long as we are fixing the dup3() interface in the way that Al
> >> and Ulrich have suggested, what about another fix:
> >>
> >> give an error if newfd is already open, thus forcing the user to do an
> >> explicit close
> >>
> >> ?
> >>
> >> This silent close in dup2() is an implementation blemish.  Why not eliminate it?
> >
> > Apart from the usual "do not break almost all existing apps" killer
> > reason: The alternative is that people will simply add a "close(newfd)"
> > everytime before "dup2(oldfd,newfd)" since close() is harmless on a
> > non-open fd.
> 
> Bernd,
> 
> I think you've missed the point.  The idea is not to change to dup2(),

That may well be. So the "eliminate it" apparently doesn't mean
"eliminate it in dup2()".

> but to eliminate the blemish in its design in the new dup3() (since we
> have alrady eliminated one other blemish).

FWIW I consider the automatic close() in dup2() a feature (if only that
it avoids an additional system call). So I would include it in dup3()
too.
But a sane, clear and consistent definition and handling of flags are
more important the auto-close() feature.

	Bernd
-- 
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