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gh-98253: Break potential reference cycles in external code worsened by typing.py lru_cache #98591

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Merged
AlexWaygood merged 3 commits into from
Nov 30, 2022
Merged

gh-98253: Break potential reference cycles in external code worsened by typing.py lru_cache #98591

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break potential reference cycles in external code worsened by typing.…
wjakob Oct 24, 2022
411fd55
added a comment clarifying the indirection
wjakob Nov 25, 2022
f27e49d
removed superfluous space
wjakob Nov 25, 2022
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added a comment clarifying the indirection
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@wjakob
wjakob committed Nov 25, 2022
commit 411fd55cb86c1cf4befe634e7363dea9599e54ac
5 changes: 5 additions & 0 deletions Lib/typing.py
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Expand Up @@ -352,6 +352,11 @@ def _tp_cache(func=None, /, *, typed=False):
original function for non-hashable arguments.
"""
def decorator(func):
# The callback 'inner' references the newly created lru_cache
# indirectly by performing a lookup in the global '_caches' dictionary.
# This breaks a reference that can be problematic when combined with
# C API extensions that leak references to types. See GH-98253.

cache = functools.lru_cache(typed=typed)(func)
_caches[func] = cache
_cleanups.append(cache.cache_clear)
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