Re: gdb pty problem [Was: emacs gud-interface is not updated after gdb command execution (maybe because of incomplete output from gdb)]

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

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On May 30 18:41, Ken Brown wrote:
> On 5/30/2016 4:02 PM, Ken Brown wrote:
> > On 5/26/2016 8:31 AM, Ken Brown wrote:
> > > This looks like a bug I reported several years ago; it actually has
> > > nothing to do with emacs:
> > > 
> > >   https://www.cygwin.com/ml/cygwin/2011-10/msg00445.html
> > > 
> > > It was fixed but then reappeared some months later:
> > > 
> > >   https://www.cygwin.com/ml/cygwin/2012-05/msg00049.html
> > > 
> > > It was fixed again but apparently is back.  The test case from the
> > > original report still exhibits the problem.
> > 
> > I've tracked down the commits that fixed this bug in the past.  The first fix was
> > 
> > commit 31d2bedc585420092eb53895c5f5646651f13215
> > Author: Christopher Faylor <me@cgf.cx>
> > Date:   Sun Oct 23 19:01:47 2011 +0000
> > 
> >     * fhandler_tty.cc (fhandler_pty_slave::read): Use consistent way for testing
> >     ReadFile return.
> >     * pipe.cc (fhandler_pipe::create_selectable): Open the write side of the pipe
> >     in message-mode to force writing as "chunks".  Explain why.
> > 
> > The second was
> > 
> > commit fb9d631817cc2b5d83c2a6ff928851d201c992bf
> > Author: Christopher Faylor <me@cgf.cx>
> > Date:   Fri May 4 03:00:43 2012 +0000
> > 
> >     * DevNotes: Add entry cgf-000002.
> >     * fhandler_tty.cc (bytes_available): Revert to previous Oct-2011 behavior where
> >     a dummy buffer is used to determine how many bytes will be read.
> >     (fhandler_pty_master::ioctl): Correct coercion in assignment.
> > 
> > A few weeks later the code was simplified:
> > 
> > commit bd8afa5eb160b56715b805befe850a5ba2131d28
> > Author: Christopher Faylor <me@cgf.cx>
> > Date:   Wed May 16 01:56:41 2012 +0000
> > 
> >     * DevNotes: Add entry cgf-000008.
> >     * fhandler_tty.cc (bytes_available): Simplify by returning the number of bytes
> >     available in the message unless that is zero.
> > 
> > I've looked at the current code in the vicinity of these changes, and nothing jumps out at me as obviously breaking the previous fixes; but that doesn't mean much.
> 
> FWIW, if I take my original test case, as modified by cgf, and uncomment the
> line "sleep (1);", then the program finishes successfully.  I don't know if
> that provides a clue.
> 
> For convenience, I'm attaching the modified test case.

Any chance you could bisect Cygwin to help finding the culprit?


Thanks,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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