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Date: Wed, 10 Sep 2003 09:34:17 -0400 (EDT)
From: Daniel Eischen <eischen@vigrid.com>
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To: Kern Sibbald <kern@sibbald.com>
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cc: Nate Lawson <nate@root.org>
cc: Dan Nelson <dnelson@allantgroup.com>
cc: Dan Langille <dan@langille.org>
Subject: Re: comments on proposed uthread_write.c changes
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On 10 Sep 2003, Kern Sibbald wrote:

> Hello,
> 
> On Wed, 2003-09-10 at 02:34, Garrett Wollman wrote:
> > <<On Tue, 9 Sep 2003 19:46:12 -0400 (EDT), Daniel Eischen <eischen@vigrid.com> said:
> > 
> > >   Libc_r's write treats a return of 0 from __sys_write() as a
> > >   partial write and continues looping.
> > 
> > This is a bug.  The Standard is quite clear that a write of zero bytes
> > is not possible unless the supplied buffer length is zero.  In the
> > specific case of non-blocking files, if data might be written but
> > doing so would cause the calling thread to block, write() must return
> > -1 with errno set to [EAGAIN]; it may not return zero.  Therefore, a
> > zero return from write() always indicates a permanent condition.
> > 
> > -GAWollman
> 
> Can you explain how you came to the conclusion that a non-zero
> write may not return zero?  Keep in mind that from the
> user's or my standpoint, we are talking about blocking
> writes.

He saying that it is an exception and should be returned
as such to the caller.

-- 
Dan Eischen