gh-88863: Clear ref cycles to resolve leak when asyncio.open_connection raises (#95739)

Break reference cycles to resolve memory leak, by
removing local exception and future instances from the frame

1 files changed, 19 insertions, 12 deletions

diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index c8a2f9f..91d32e3 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -986,6 +986,8 @@ class BaseEventLoop(events.AbstractEventLoop):
             if sock is not None:
                 sock.close()
             raise
+        finally:
+            exceptions = my_exceptions = None
 
     async def create_connection(
             self, protocol_factory, host=None, port=None,
@@ -1084,19 +1086,22 @@ class BaseEventLoop(events.AbstractEventLoop):
 
             if sock is None:
                 exceptions = [exc for sub in exceptions for exc in sub]
-                if all_errors:
-                    raise ExceptionGroup("create_connection failed", exceptions)
-                if len(exceptions) == 1:
-                    raise exceptions[0]
-                else:
-                    # If they all have the same str(), raise one.
-                    model = str(exceptions[0])
-                    if all(str(exc) == model for exc in exceptions):
+                try:
+                    if all_errors:
+                        raise ExceptionGroup("create_connection failed", exceptions)
+                    if len(exceptions) == 1:
                         raise exceptions[0]
-                    # Raise a combined exception so the user can see all
-                    # the various error messages.
-                    raise OSError('Multiple exceptions: {}'.format(
-                        ', '.join(str(exc) for exc in exceptions)))
+                    else:
+                        # If they all have the same str(), raise one.
+                        model = str(exceptions[0])
+                        if all(str(exc) == model for exc in exceptions):
+                            raise exceptions[0]
+                        # Raise a combined exception so the user can see all
+                        # the various error messages.
+                        raise OSError('Multiple exceptions: {}'.format(
+                            ', '.join(str(exc) for exc in exceptions)))
+                finally:
+                    exceptions = None
 
         else:
             if sock is None:
@@ -1904,6 +1909,8 @@ class BaseEventLoop(events.AbstractEventLoop):
 
         event_list = self._selector.select(timeout)
         self._process_events(event_list)
+        # Needed to break cycles when an exception occurs.
+        event_list = None
 
         # Handle 'later' callbacks that are ready.
         end_time = self.time() + self._clock_resolution