From 7be36cb53ba54e3ca8ef668425bf269dfcd8c735 Mon Sep 17 00:00:00 2001
From: Andrew Straw <strawman@astraw.com>
Date: Mon, 27 Nov 2023 17:44:55 +0100
Subject: [PATCH] Clear input/output buffers on macOS upon TTY open

I don't understand why this works, but it resolves problematic behavior
(#49) on macOS. Bisecting history, I found commit
3d6c1b25e3430e45290da752e01da96e81beddc3, which removed flushing the IO
buffers for a TTY, was problematic on macOS. However, the test
`test_osx_pty_pair` which tests pseudo-ttys with baud_rate 0 on macOS
(introduced in b54264b2588879bdca4aeb69c5b91f8a4bf980cb) fails if I
simply reintroduced flushing. Therefore, this change now re-introduces
flushing the IO buffers upon opening a TTY, but only on macOS and only
when baud-rate is non-zero.

Thanks to @berkus for the original work.
---
 src/posix/tty.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/posix/tty.rs b/src/posix/tty.rs
index e6a83ecd..c21cf2d1 100644
--- a/src/posix/tty.rs
+++ b/src/posix/tty.rs
@@ -156,6 +156,11 @@ impl TTYPort {
             ));
         };
 
+        #[cfg(any(target_os = "ios", target_os = "macos"))]
+        if builder.baud_rate > 0 {
+            unsafe { libc::tcflush(fd.0, libc::TCIOFLUSH) };
+        }
+
         // clear O_NONBLOCK flag
         fcntl(fd.0, F_SETFL(nix::fcntl::OFlag::empty()))?;