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bpo-30306: release arguments of contextmanager (GH-1500)

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The arguments to a generator function which is declared as a
contextmanager are stored inside the context manager, and
thus are kept alive, even when it is used as a regular context
manager, and not as a function decorator (where it needs
the original arguments to recreate the generator on each
call).

This is a possible unnecessary memory leak, so this changes
contextmanager.__enter__ to release the saved arguments,
as that method being called means that particular CM instance
isn't going to need to recreate the underlying generator.

Patch by Martin Teichmann.
This commit is contained in:
Martin Teichmann 2018-01-28 05:17:46 +01:00 • committed by Nick Coghlan
parent c4b1248308
commit dd0e087edc
2 changed files with 50 additions and 0 deletions
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3
Lib/contextlib.py
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@ -105,6 +105,9 @@ class _GeneratorContextManager(_GeneratorContextManagerBase,
return self.__class__(self.func, self.args, self.kwds)
def __enter__(self):
# do not keep args and kwds alive unnecessarily
# they are only needed for recreation, which is not possible anymore
del self.args, self.kwds, self.func
try:
return next(self.gen)
except StopIteration: