Fixed leaked sock states, issue tokio-rs#1146. A reference of the soc…

…k state Arc is blocked by a pending afd poll request, this reference will leak if there's no explicit poll done before the program terminates. That's why

doing an explicit "select" during iner selector drop ensures all sock state references are freed.

Signed-off-by: Daniel Tacalau <dst4096@gmail.com>

src/sys/windows/selector.rs

@@ -391,6 +391,20 @@ pub struct SelectorInner {
 // We have ensured thread safety by introducing lock manually.
 unsafe impl Sync for SelectorInner {}
 
+impl Drop for SelectorInner {
+    fn drop(&mut self) {
+        loop {
+            let mut events = Events::with_capacity(1024);
+            let _ = self.select(&mut events, Some(std::time::Duration::from_millis(0)));
+            if events.events.len() < 1024 {
+                break;
+            }
+        }
+
+        self.afd_group.release_unused_afd();
+    }
+}
+
 impl SelectorInner {
     pub fn new() -> io::Result<SelectorInner> {
         CompletionPort::new(0).map(|cp| {