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✏️ Editing: test_refcounts.py

import unittest
from test import support
import ctypes
import gc

MyCallback = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_int)
OtherCallback = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_int, ctypes.c_ulonglong)

import _ctypes_test
dll = ctypes.CDLL(_ctypes_test.__file__)

class RefcountTestCase(unittest.TestCase):

@support.refcount_test
    def test_1(self):
        from sys import getrefcount as grc

f = dll._testfunc_callback_i_if
        f.restype = ctypes.c_int
        f.argtypes = [ctypes.c_int, MyCallback]

def callback(value):
            #print "called back with", value
            return value

self.assertEqual(grc(callback), 2)
        cb = MyCallback(callback)

self.assertGreater(grc(callback), 2)
        result = f(-10, cb)
        self.assertEqual(result, -18)
        cb = None

gc.collect()

self.assertEqual(grc(callback), 2)

@support.refcount_test
    def test_refcount(self):
        from sys import getrefcount as grc
        def func(*args):
            pass
        # this is the standard refcount for func
        self.assertEqual(grc(func), 2)

# the CFuncPtr instance holds at least one refcount on func:
        f = OtherCallback(func)
        self.assertGreater(grc(func), 2)

# and may release it again
        del f
        self.assertGreaterEqual(grc(func), 2)

# but now it must be gone
        gc.collect()
        self.assertEqual(grc(func), 2)

class X(ctypes.Structure):
            _fields_ = [("a", OtherCallback)]
        x = X()
        x.a = OtherCallback(func)

# the CFuncPtr instance holds at least one refcount on func:
        self.assertGreater(grc(func), 2)

# and may release it again
        del x
        self.assertGreaterEqual(grc(func), 2)

# and now it must be gone again
        gc.collect()
        self.assertEqual(grc(func), 2)

f = OtherCallback(func)

# the CFuncPtr instance holds at least one refcount on func:
        self.assertGreater(grc(func), 2)

# create a cycle
        f.cycle = f

del f
        gc.collect()
        self.assertEqual(grc(func), 2)

class AnotherLeak(unittest.TestCase):
    def test_callback(self):
        import sys

proto = ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_int, ctypes.c_int)
        def func(a, b):
            return a * b * 2
        f = proto(func)

a = sys.getrefcount(ctypes.c_int)
        f(1, 2)
        self.assertEqual(sys.getrefcount(ctypes.c_int), a)

@support.refcount_test
    def test_callback_py_object_none_return(self):
        # bpo-36880: test that returning None from a py_object callback
        # does not decrement the refcount of None.

for FUNCTYPE in (ctypes.CFUNCTYPE, ctypes.PYFUNCTYPE):
            with self.subTest(FUNCTYPE=FUNCTYPE):
                @FUNCTYPE(ctypes.py_object)
                def func():
                    return None

# Check that calling func does not affect None's refcount.
                for _ in range(10000):
                    func()

if __name__ == '__main__':
    unittest.main()

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