extmod/modselect: Properly track number of poll objects that are fd's.

Signed-off-by: Damien George <damien@micropython.org>

tests/extmod/select_poll_custom.py

@@ -77,7 +77,26 @@ try:
 except OSError as er:
     print("OSError", er.errno)
 
+# Register then unregister a socket (a native stream), then test
+# that the Python object is still pollable.
+s2 = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+x.poll_state = _MP_STREAM_POLL_RD
+poller.register(s2)
+poller.unregister(s2)
+print_poll_output(poller.poll())
+
+# Test registering and unregistering multiple times.
+for _ in range(2):
+    poller.unregister(s)
+    poller.unregister(x)
+    poller.register(s2)
+    poller.register(s, select.POLLIN)
+    poller.register(x, select.POLLIN)
+    poller.unregister(s2)
+    print_poll_output(poller.poll())
+
+# Clean up.
 poller.unregister(x)
 poller.unregister(s)
-
+s2.close()
 s.close()

tests/extmod/select_poll_custom.py.exp

@@ -9,3 +9,9 @@ CustomPollable.ioctl 3 1
 [(<class 'CustomPollable'>, 1)]
 CustomPollable.ioctl 3 1
 OSError 1000
+CustomPollable.ioctl 3 1
+[(<class 'CustomPollable'>, 1)]
+CustomPollable.ioctl 3 1
+[(<class 'CustomPollable'>, 1)]
+CustomPollable.ioctl 3 1
+[(<class 'CustomPollable'>, 1)]