diff --git a/Lib/concurrent/futures/_base.py b/Lib/concurrent/futures/_base.py index 4c140508c9eaec..9ac2e6b32f3ddd 100644 --- a/Lib/concurrent/futures/_base.py +++ b/Lib/concurrent/futures/_base.py @@ -381,7 +381,11 @@ def done(self): def __get_result(self): if self._exception: - raise self._exception + try: + raise self._exception + finally: + # Break a reference cycle with the exception in self._exception + self = None else: return self._result @@ -418,20 +422,24 @@ def result(self, timeout=None): timeout. Exception: If the call raised then that exception will be raised. """ - with self._condition: - if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: - raise CancelledError() - elif self._state == FINISHED: - return self.__get_result() - - self._condition.wait(timeout) - - if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: - raise CancelledError() - elif self._state == FINISHED: - return self.__get_result() - else: - raise TimeoutError() + try: + with self._condition: + if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: + raise CancelledError() + elif self._state == FINISHED: + return self.__get_result() + + self._condition.wait(timeout) + + if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: + raise CancelledError() + elif self._state == FINISHED: + return self.__get_result() + else: + raise TimeoutError() + finally: + # Break a reference cycle with the exception in self._exception + self = None def exception(self, timeout=None): """Return the exception raised by the call that the future represents. diff --git a/Misc/NEWS.d/next/Library/2021-03-23-17-18-56.bpo-35930.RZ51pM.rst b/Misc/NEWS.d/next/Library/2021-03-23-17-18-56.bpo-35930.RZ51pM.rst new file mode 100644 index 00000000000000..71c6012f52b8f1 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-03-23-17-18-56.bpo-35930.RZ51pM.rst @@ -0,0 +1,2 @@ +Raising an exception raised in a "future" instance will create reference +cycles.