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[3.13] gh-144100: Fix crash for POINTER(str) used in ctypes argtypes (#144108) #144245

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Merged
vstinner merged 1 commit into from
Jan 27, 2026
Merged

[3.13] gh-144100: Fix crash for POINTER(str) used in ctypes argtypes (#144108) #144245

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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 @@ -235,6 +235,17 @@ class C(Structure):
ptr.set_type(c_int)
self.assertIs(ptr._type_, c_int)

def test_pointer_proto_missing_argtypes_error(self):
class BadType(ctypes._Pointer):
# _type_ is intentionally missing
pass

func = ctypes.pythonapi.Py_GetVersion
func.argtypes = (BadType,)

with self.assertRaises(ctypes.ArgumentError):
func(object())


if __name__ == '__main__':
unittest.main()
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-01-21-19-39-07.gh-issue-144100.hLMZ8Y.rst
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@@ -0,0 +1,3 @@
Fixed a crash in ctypes when using a deprecated ``POINTER(str)`` type in
``argtypes``. Instead of aborting, ctypes now raises a proper Python
exception when the pointer target type is unresolved.
8 changes: 7 additions & 1 deletion Modules/_ctypes/_ctypes.c
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Expand Up @@ -1338,7 +1338,13 @@ PyCPointerType_from_param_impl(PyObject *type, PyTypeObject *cls,
/* If we expect POINTER(<type>), but receive a <type> instance, accept
it by calling byref(<type>).
*/
assert(typeinfo->proto);
if (typeinfo->proto == NULL) {
PyErr_SetString(
PyExc_TypeError,
"cannot convert argument: POINTER _type_ type is not set"
);
return NULL;
}
switch (PyObject_IsInstance(value, typeinfo->proto)) {
case 1:
Py_INCREF(value); /* _byref steals a refcount */
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