Remove workaround for python/cpython#81061.

changes/517.bugfix.rst

@@ -0,0 +1 @@
+A workaround for python/cpython#81061 was conditionally removed when running under Python 3.9 or earlier.

src/rubicon/objc/ctypes_patch.py

@@ -81,12 +81,17 @@ class ffi_type(ctypes.Structure):
 
 # The GETFUNC and SETFUNC typedefs from "Modules/_ctypes/ctypes.h".
 GETFUNC = ctypes.PYFUNCTYPE(ctypes.py_object, ctypes.c_void_p, ctypes.c_ssize_t)
-# The return type of SETFUNC is declared here as a c_void_p instead of py_object to work
-# around a ctypes bug (https://github.com/python/cpython/issues/81061). See the comment
-# in make_callback_returnable's setfunc for details.
-SETFUNC = ctypes.PYFUNCTYPE(
-    ctypes.c_void_p, ctypes.c_void_p, ctypes.py_object, ctypes.c_ssize_t
-)
+if sys.version_info < (3, 10):
+    # The return type of SETFUNC is declared here as a c_void_p instead of py_object to work
+    # around a ctypes bug (https://github.com/python/cpython/issues/81061). See the comment
+    # in make_callback_returnable's setfunc for details. This bug was fixed in 3.10.
+    SETFUNC = ctypes.PYFUNCTYPE(
+        ctypes.c_void_p, ctypes.c_void_p, ctypes.py_object, ctypes.c_ssize_t
+    )
+else:
+    SETFUNC = ctypes.PYFUNCTYPE(
+        ctypes.py_object, ctypes.c_void_p, ctypes.py_object, ctypes.c_ssize_t
+    )
 
 
 if sys.version_info < (3, 13):
@@ -287,20 +292,22 @@ def setfunc(ptr, value, size):
             )
 
         ctypes.memmove(ptr, ctypes.addressof(value), actual_size)
-        # Because of a ctypes bug (https://github.com/python/cpython/issues/81061),
-        # returning None from a callback with restype py_object causes a reference
-        # counting error that can crash Python. To work around this bug, the restype of
-        # SETFUNC is declared as c_void_p instead. This way ctypes performs no automatic
-        # reference counting for the returned object, which avoids the bug. However,
-        # this way we have to manually convert the Python object to a pointer and adjust
-        # its reference count.
-        none_ptr = ctypes.cast(id(None), ctypes.POINTER(PyObject))
-        # The return value of a SETFUNC is expected to have an extra reference
-        # (which will be owned by the caller of the SETFUNC).
-        ctypes.pythonapi.Py_IncRef(none_ptr)
-        # The returned pointer must be returned as a plain int, not as a c_void_p,
-        # otherwise ctypes won't recognize it and will raise a TypeError.
-        return ctypes.cast(none_ptr, ctypes.c_void_p).value
+
+        if sys.version_info < (3, 10):
+            # Because of a ctypes bug (https://github.com/python/cpython/issues/81061),
+            # returning None from a callback with restype py_object causes a reference
+            # counting error that can crash Python. To work around this bug, the restype of
+            # SETFUNC is declared as c_void_p instead. This way ctypes performs no automatic
+            # reference counting for the returned object, which avoids the bug. However,
+            # this way we have to manually convert the Python object to a pointer and adjust
+            # its reference count. This bug was fixed in 3.10.
+            none_ptr = ctypes.cast(id(None), ctypes.POINTER(PyObject))
+            # The return value of a SETFUNC is expected to have an extra reference
+            # (which will be owned by the caller of the SETFUNC).
+            ctypes.pythonapi.Py_IncRef(none_ptr)
+            # The returned pointer must be returned as a plain int, not as a c_void_p,
+            # otherwise ctypes won't recognize it and will raise a TypeError.
+            return ctypes.cast(none_ptr, ctypes.c_void_p).value
 
     # Store the getfunc and setfunc as attributes on the ctype, so they don't
     # get garbage-collected.