#From lib-python/3/test/_test_multiprocessing.py
class _Foo(Structure):
    _fields_ = [
        ('x', c_int),
        ('y', c_double)
        ]

def test_copy(self):
    foo = _Foo(2, 5.0)
    bar = copy(foo)
    foo.x = 0
    foo.y = 0
    self.assertEqual(bar.x, 2)
    self.assertAlmostEqual(bar.y, 5.0)

#This goes to the sharedctypes of multiprocessing
def copy(obj):
    new_obj = _new_value(type(obj))
    ctypes.pointer(new_obj)[0] = obj
    return new_obj

#Which then breaks here
def __setitem__(self, index, value):
   cobj = self._type_.from_param(value)
   if ensure_objects(cobj) is not None:
       store_reference(self, index, cobj._objects)
   self._subarray(index)[0] = cobj._get_buffer_value()
   #At this last line

The error:

ERROR: test_copy (test.test_multiprocessing_forkserver.WithProcessesTestSharedCTypes)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/extra1/home/buildslave/buildslave/pypy-c-app-level-linux-x86-64/build/lib-python/3/test/_test_multiprocessing.py", line 2876, in test_copy
    bar = copy(foo)
  File "/extra1/home/buildslave/buildslave/pypy-c-app-level-linux-x86-64/build/lib-python/3/multiprocessing/sharedctypes.py", line 99, in copy
    ctypes.pointer(new_obj)[0] = obj
  File "/extra1/home/buildslave/buildslave/pypy-c-app-level-linux-x86-64/build/lib_pypy/_ctypes/pointer.py", line 116, in __setitem__
    self._subarray(index)[0] = cobj._get_buffer_value()
TypeError: 'StructureInstance' object does not support item assignment