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gh-133290: Use PyObject_SetAttr to set _type_ #133292

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Merged
merged 3 commits into from
May 2, 2025
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gh-133290: Use PyObject_SetAttr to set _type_ #133292

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f475056
gh-133290: Use PyObject_SetAttr to set _type_
encukou May 2, 2025
3e2dc35
blurb
encukou May 2, 2025
05eb47d
Don't reference an undocumented function
encukou May 2, 2025
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11 changes: 11 additions & 0 deletions Lib/test/test_ctypes/test_pointers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -224,6 +224,17 @@ def test_pointer_type_str_name(self):
def test_abstract(self):
self.assertRaises(TypeError, _Pointer.set_type, 42)

def test_repeated_set_type(self):
# Regression test for gh-133290
class C(Structure):
_fields_ = [('a', c_int)]
ptr = POINTER(C)
# Read _type_ several times to warm up cache
for i in range(5):
self.assertIs(ptr._type_, C)
ptr.set_type(c_int)
self.assertIs(ptr._type_, c_int)


if __name__ == '__main__':
unittest.main()
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2025-05-02-13-16-44.gh-issue-133290.R5WrLM.rst
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@@ -0,0 +1,3 @@
Fix attribute caching issue when setting :attr:`ctypes._Pointer._type_` in
the undocumented and deprecated :func:`!ctypes.SetPointerType` function and the
undocumented :meth:`!set_type` method.
12 changes: 1 addition & 11 deletions Modules/_ctypes/_ctypes.c
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Expand Up @@ -1298,34 +1298,24 @@ PyCPointerType_set_type_impl(PyTypeObject *self, PyTypeObject *cls,
PyObject *type)
/*[clinic end generated code: output=51459d8f429a70ac input=67e1e8df921f123e]*/
{
PyObject *attrdict = PyType_GetDict(self);
if (!attrdict) {
return NULL;
}
ctypes_state *st = get_module_state_by_class(cls);
StgInfo *info;
if (PyStgInfo_FromType(st, (PyObject *)self, &info) < 0) {
Py_DECREF(attrdict);
return NULL;
}
if (!info) {
PyErr_SetString(PyExc_TypeError,
"abstract class");
Py_DECREF(attrdict);
return NULL;
}

if (PyCPointerType_SetProto(st, info, type) < 0) {
Py_DECREF(attrdict);
return NULL;
}

if (-1 == PyDict_SetItem(attrdict, &_Py_ID(_type_), type)) {
Py_DECREF(attrdict);
if (PyObject_SetAttr((PyObject *)self, &_Py_ID(_type_), type) < 0) {
return NULL;
}

Py_DECREF(attrdict);
Py_RETURN_NONE;
}

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