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[3.13] gh-146615: Fix crash in __get__() for METH_METHOD descriptors with invalid type argument (GH-146634) #146648

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Merged
serhiy-storchaka merged 1 commit into from
Mar 31, 2026
Merged

[3.13] gh-146615: Fix crash in __get__() for METH_METHOD descriptors with invalid type argument (GH-146634) #146648

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gh-146615: Fix crash in __get__() for METH_METHOD descriptors with in… 
…valid type argument (GH-146634)

(cherry picked from commit 72d29ea)

Co-authored-by: sunmy2019 <59365878+sunmy2019@users.noreply.github.com>
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@sunmy2019 @miss-islington
sunmy2019 authored and miss-islington committed Mar 31, 2026
commit 20c327aff8f2cfce56af44891e2f84639e4b2edd
22 changes: 22 additions & 0 deletions Lib/test/test_descr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1662,6 +1662,28 @@ class SubSpam(spam.spamlist): pass
spam_cm.__get__(None, list)
self.assertEqual(str(cm.exception), expected_errmsg)

@support.cpython_only
def test_method_get_meth_method_invalid_type(self):
# gh-146615: method_get() for METH_METHOD descriptors used to pass
# Py_TYPE(type)->tp_name as the %V fallback instead of the separate
# %s argument, causing a missing argument for %s and a crash.
# Verify the error message is correct when __get__() is called with a
# non-type as the second argument.
#
# METH_METHOD|METH_FASTCALL|METH_KEYWORDS is the only flag combination
# that enters the affected branch in method_get().
import io

obj = io.StringIO()
descr = io.TextIOBase.read

with self.assertRaises(TypeError) as cm:
descr.__get__(obj, "not_a_type")
self.assertEqual(
str(cm.exception),
"descriptor 'read' needs a type, not 'str', as arg 2",
)

def test_staticmethods(self):
# Testing static methods...
class C(object):
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3 changes: 3 additions & 0 deletions ...d/next/Core_and_Builtins/2026-03-31-01-06-35.gh-issue-146615.fix-method-get.rst
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@@ -0,0 +1,3 @@
Fix a crash in :meth:`~object.__get__` for :c:expr:`METH_METHOD` descriptors
when an invalid (non-type) object is passed as the second argument.
Patch by Steven Sun.
2 changes: 1 addition & 1 deletion Objects/descrobject.c
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Expand Up @@ -149,7 +149,7 @@ method_get(PyObject *self, PyObject *obj, PyObject *type)
} else {
PyErr_Format(PyExc_TypeError,
"descriptor '%V' needs a type, not '%s', as arg 2",
descr_name((PyDescrObject *)descr),
descr_name((PyDescrObject *)descr), "?",
Py_TYPE(type)->tp_name);
return NULL;
}
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