gh-118013: Use weakrefs for the cache key in inspect._shadowed_dict

Lib/inspect.py

@@ -160,6 +160,7 @@
 from keyword import iskeyword
 from operator import attrgetter
 from collections import namedtuple, OrderedDict
+from weakref import ref as make_weakref
 
 # Create constants for the compiler flags in Include/code.h
 # We try to get them from dis to avoid duplication
@@ -1832,9 +1833,11 @@ def _check_class(klass, attr):
             return entry.__dict__[attr]
     return _sentinel
 
+
 @functools.lru_cache()
-def _shadowed_dict_from_mro_tuple(mro):
-    for entry in mro:
+def _shadowed_dict_from_weakref_mro_tuple(*weakref_mro):
+    for weakref_entry in weakref_mro:
+        entry = weakref_entry()
         dunder_dict = _get_dunder_dict_of_class(entry)
         if '__dict__' in dunder_dict:
             class_dict = dunder_dict['__dict__']
@@ -1844,8 +1847,12 @@ def _shadowed_dict_from_mro_tuple(mro):
                 return class_dict
     return _sentinel
 
+
 def _shadowed_dict(klass):
-    return _shadowed_dict_from_mro_tuple(_static_getmro(klass))
+    return _shadowed_dict_from_weakref_mro_tuple(
+        *[make_weakref(entry) for entry in _static_getmro(klass)]
+    )
+
 
 def getattr_static(obj, attr, default=_sentinel):
     """Retrieve attributes without triggering dynamic lookup via the

Lib/test/libregrtest/utils.py

@@ -275,7 +275,6 @@ def clear_caches():
     except KeyError:
         pass
     else:
-        inspect._shadowed_dict_from_mro_tuple.cache_clear()
         inspect._filesbymodname.clear()
         inspect.modulesbyfile.clear()