Issue #23209: Break some reference cycles in asyncio. Patch written by Martin

Richard.

Lib/asyncio/base_subprocess.py

@@ -182,6 +182,7 @@ class WriteSubprocessPipeProto(protocols.BaseProtocol):
     def connection_lost(self, exc):
         self.disconnected = True
         self.proc._pipe_connection_lost(self.fd, exc)
+        self.proc = None
 
     def pause_writing(self):
         self.proc._protocol.pause_writing()

Lib/asyncio/futures.py

@@ -405,5 +405,5 @@ def wrap_future(fut, *, loop=None):
     new_future.add_done_callback(_check_cancel_other)
     fut.add_done_callback(
         lambda future: loop.call_soon_threadsafe(
-            new_future._copy_state, fut))
+            new_future._copy_state, future))
     return new_future

Lib/selectors.py

@@ -256,6 +256,7 @@ class _BaseSelectorImpl(BaseSelector):
 
     def close(self):
         self._fd_to_key.clear()
+        self._map = None
 
     def get_map(self):
         return self._map