Hi,

I think I am experiencing a problem with fifos on cygwin. The attached
C source (fifocomm.c) creates two pipes (/tmp/pipe.{in,out}), expecting
to receive inputs from /tmp/pipe.in and replying to /tmp/pipe.out.

Compiling this source on linux and launching it produces on the terminal

1) Opening pipes

and then the program waits for someone to write to /tmp/pipe.in.
Opening another terminal and launching the fifotest.sh script (also
attached) produces on the first terminal

1) Closing pipes
2) Opening pipes

and the program continues waiting for another input, while the other
terminal shows "You sent: foo"

Instead, on cygwin, after launching the program one gets:

1) Opening pipes
1) Closing pipes
2) Opening pipes
2) Closing pipes
3) Opening pipes
3) Closing pipes
4) Opening pipes
....
....

meaning that the pipes are continually closed and reopened even if
nobody is writing to /tmp/pipe.in.

Seemingly, the problem is the return value of read() on line 55.
As O_NONBLOCK is set, until no data is available for reading,
read() shouldn't block but should return -1 and set errno to EAGAIN.
After a client that opened the pipe for writing, closes it
(and no other client is using the pipe), read() should return 0 and
only at this point the pipes have to be closed and reopened.

However, on cygwin, read() returns 0 also when nobody is writing to the
input pipe causing the above ping pong. As already said, it works as it
should on linux.

-- 
Enrico