[PATCH] Cygwin: pty: Make system_printf() work after closing pty slave.

[Ken Brown]

Hi Takashi,

On 5/19/2020 7:35 AM, Takashi Yano via Cygwin-patches wrote:
> - Current pty cannot show system_printf() output after closing pty
>    slave. This patch fixes the issue.

Sorry to be returning the favor so soon, but this patch causes 'make check' in 
the texinfo source tree to hang.  I don't have time at the moment to try to 
produce a simple test case, so here's a complicated way to reproduce the problem:

1. Clone the texinfo git repo:

   $ git clone https://git.savannah.gnu.org/git/texinfo.git

2. Build texinfo:

   $ cd texinfo
   $ ./autogen.sh && ./configure # Maybe CFLAGS='-g -O0' for debugging
   $ make

3. Test the standalone info reader:

   $ cd info
   $ make check

It hangs while running the test t/malformed-split.sh, leaving a ginfo process 
and a pseudotty process running, with ginfo trying to close a pty slave.

Note that this test uses both ptys and fifos, so there's always a chance that 
this is another fifo bug.  But reverting your patch fixes the problem, so I 
think it's probably a pty bug.

Ken