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Subject: Re: [Qemu-devel] [PATCH] flush stdout after printing usage()
From: Lionel Landwerlin <lionel.landwerlin@openwide.fr>
In-Reply-To: <20090128210639.GB4155@kos.to>
References: <20090128184713.GA29581@kos.to> <4980BBC2.3050709@codemonkey.ws>
	<20090128210639.GB4155@kos.to>
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Date: Wed, 28 Jan 2009 22:51:25 +0100
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To: qemu-devel@nongnu.org

Le mercredi 28 janvier 2009 =C3=A0 23:06 +0200, Riku Voipio a =C3=A9crit =
:
> On Wed, Jan 28, 2009 at 02:10:42PM -0600, Anthony Liguori wrote:
> > Riku Voipio wrote:
> > >testcase:
> > >
> > >qemu-arm|grep cpu
> > >
> > >Without fflush() getting output from piped qemu is a bit random.
>=20
> > It should get flushed upon exit(). Perhaps the problem is that we're=20
> > using _exit() instead of exit()?
>=20

_exit does not trigger callbacks registred with at_exit.

from the man page :

       The function _exit() is like exit(3), but does not call  any  func=
tions
       registered  with  atexit(3) or on_exit(3).  Whether it flushes sta=
ndard
       I/O buffers and removes temporary  files  created  with  tmpfile(3=
)  is
       implementation-dependent.   On  the other hand, _exit() does close=
 open
       file descriptors, and this may cause  an  unknown  delay,  waiting=
  for
       pending  output to finish.  If the delay is undesired, it may be u=
seful
       to call functions like tcflush(3) before calling _exit().  Whether=
  any
       pending  I/O  is  canceled,  and which pending I/O may be canceled=
 upon
       _exit(), is implementation-dependent.