[PATCH] Cygwin: console: Clear readahead buffer on tcflush()

Previously, tcflush(TCIFLUSH) only discarded the input events and
did not clear the readahead buffer. Because of this bug, when user
program called select() -> tcflush() -> read(), the last read()
returned the contents of the readahead buffer instead of blocking
as it should.

Correctly, tcflush() must discard all pending input, so read()
should block until new input arrives. With this patch, the read-
ahead buffer is also cleared as well as input events.

Fixes: 8382778cdb57 ("Cygwin: console: fix select() behaviour")
Suggested-by: Johannes Schindelin <[email protected]>
Signed-off-by: Takashi Yano <[email protected]>
Reviewed-by:
---
 winsup/cygwin/fhandler/console.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/winsup/cygwin/fhandler/console.cc b/winsup/cygwin/fhandler/console.cc
index ba35ca44c..d3fb2fcbd 100644
--- a/winsup/cygwin/fhandler/console.cc
+++ b/winsup/cygwin/fhandler/console.cc
@@ -2362,6 +2362,8 @@ fhandler_console::tcflush (int queue)
 	  res = -1;
 	}
       con.num_processed = 0;
+      eat_readahead (-1);
+      input_ready = false;
     }
   return res;
 }
-- 
2.51.0