Re: [Qemu-devel] [PATCH] flush stdout after printing usage()

[Anthony Liguori <anthony@codemonkey.ws>]

Lionel Landwerlin wrote:
> Le mercredi 28 janvier 2009 à 23:06 +0200, Riku Voipio a écrit :
>   
>> 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.
>>>>         
>>> It should get flushed upon exit(). Perhaps the problem is that we're 
>>> using _exit() instead of exit()?
>>>       
>
> _exit does not trigger callbacks registred with at_exit.
>   

Yes.  The question is why is it being used?  What at_exit handler are we 
trying to avoid.

Regards,

Anthony Liguori

> from the man page :
>
>        The function _exit() is like exit(3), but does not call  any  functions
>        registered  with  atexit(3) or on_exit(3).  Whether it flushes standard
>        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 useful
>        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.
>
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