important info consider this call func restype ccharp funcccharp123 it returns 123 why is this so argument tuple ccharp123 is destroyed after the function func is called but not before the result is actually built if the arglist would be destroyed before the result has been built the ccharp123 object would already have a zero refcount and the pointer passed to and returned by the function would probably point to deallocated space in this case there would have to be an additional reference to the argument return machine address a as a possibly long nonnegative integer starting with python 2 5 idanything is always nonnegative and the ctypes addressof inherits that via pylongfromvoidptr view the bits in a as unsigned instead function returns cvoidp result and has a required parameter named input xxx currently these raise typeerrors although they shouldn t this did crash before important info consider this call func restype c_char_p func c_char_p 123 it returns 123 why is this so argument tuple c_char_p 123 is destroyed after the function func is called but not before the result is actually built if the arglist would be destroyed before the result has been built the c_char_p 123 object would already have a zero refcount and the pointer passed to and returned by the function would probably point to deallocated space in this case there would have to be an additional reference to the argument return machine address a as a possibly long non negative integer starting with python 2 5 id anything is always non negative and the ctypes addressof inherits that via pylong_fromvoidptr view the bits in a as unsigned instead num bits in native machine address function returns c_void_p result and has a required parameter named input xxx currently these raise typeerrors although they shouldn t this did crash before
import _ctypes_test
import unittest
from ctypes import (CDLL, CFUNCTYPE, POINTER, ArgumentError,
                    pointer, byref, sizeof, addressof, create_string_buffer,
                    c_void_p, c_char_p, c_wchar_p, c_char, c_wchar,
                    c_short, c_int, c_long, c_longlong, c_double)


testdll = CDLL(_ctypes_test.__file__)





def positive_address(a):
    if a >= 0:
        return a
    
    import struct
    num_bits = struct.calcsize("P") * 8 
    a += 1 << num_bits
    assert a >= 0
    return a


def c_wbuffer(init):
    n = len(init) + 1
    return (c_wchar * n)(*init)


class CharPointersTestCase(unittest.TestCase):
    def setUp(self):
        func = testdll._testfunc_p_p
        func.restype = c_long
        func.argtypes = None

    def test_paramflags(self):
        
        
        prototype = CFUNCTYPE(c_void_p, c_void_p)
        func = prototype(("_testfunc_p_p", testdll),
                         ((1, "input"),))

        try:
            func()
        except TypeError as details:
            self.assertEqual(str(details), "required argument 'input' missing")
        else:
            self.fail("TypeError not raised")

        self.assertEqual(func(None), None)
        self.assertEqual(func(input=None), None)


    def test_int_pointer_arg(self):
        func = testdll._testfunc_p_p
        if sizeof(c_longlong) == sizeof(c_void_p):
            func.restype = c_longlong
        else:
            func.restype = c_long
        self.assertEqual(0, func(0))

        ci = c_int(0)

        func.argtypes = POINTER(c_int),
        self.assertEqual(positive_address(addressof(ci)),
                             positive_address(func(byref(ci))))

        func.argtypes = c_char_p,
        self.assertRaises(ArgumentError, func, byref(ci))

        func.argtypes = POINTER(c_short),
        self.assertRaises(ArgumentError, func, byref(ci))

        func.argtypes = POINTER(c_double),
        self.assertRaises(ArgumentError, func, byref(ci))

    def test_POINTER_c_char_arg(self):
        func = testdll._testfunc_p_p
        func.restype = c_char_p
        func.argtypes = POINTER(c_char),

        self.assertEqual(None, func(None))
        self.assertEqual(b"123", func(b"123"))
        self.assertEqual(None, func(c_char_p(None)))
        self.assertEqual(b"123", func(c_char_p(b"123")))

        self.assertEqual(b"123", func(create_string_buffer(b"123")))
        ca = c_char(b"a")
        self.assertEqual(ord(b"a"), func(pointer(ca))[0])
        self.assertEqual(ord(b"a"), func(byref(ca))[0])

    def test_c_char_p_arg(self):
        func = testdll._testfunc_p_p
        func.restype = c_char_p
        func.argtypes = c_char_p,

        self.assertEqual(None, func(None))
        self.assertEqual(b"123", func(b"123"))
        self.assertEqual(None, func(c_char_p(None)))
        self.assertEqual(b"123", func(c_char_p(b"123")))

        self.assertEqual(b"123", func(create_string_buffer(b"123")))
        ca = c_char(b"a")
        self.assertEqual(ord(b"a"), func(pointer(ca))[0])
        self.assertEqual(ord(b"a"), func(byref(ca))[0])

    def test_c_void_p_arg(self):
        func = testdll._testfunc_p_p
        func.restype = c_char_p
        func.argtypes = c_void_p,

        self.assertEqual(None, func(None))
        self.assertEqual(b"123", func(b"123"))
        self.assertEqual(b"123", func(c_char_p(b"123")))
        self.assertEqual(None, func(c_char_p(None)))

        self.assertEqual(b"123", func(create_string_buffer(b"123")))
        ca = c_char(b"a")
        self.assertEqual(ord(b"a"), func(pointer(ca))[0])
        self.assertEqual(ord(b"a"), func(byref(ca))[0])

        func(byref(c_int()))
        func(pointer(c_int()))
        func((c_int * 3)())

    def test_c_void_p_arg_with_c_wchar_p(self):
        func = testdll._testfunc_p_p
        func.restype = c_wchar_p
        func.argtypes = c_void_p,

        self.assertEqual(None, func(c_wchar_p(None)))
        self.assertEqual("123", func(c_wchar_p("123")))

    def test_instance(self):
        func = testdll._testfunc_p_p
        func.restype = c_void_p

        class X:
            _as_parameter_ = None

        func.argtypes = c_void_p,
        self.assertEqual(None, func(X()))

        func.argtypes = None
        self.assertEqual(None, func(X()))


class WCharPointersTestCase(unittest.TestCase):
    def setUp(self):
        func = testdll._testfunc_p_p
        func.restype = c_int
        func.argtypes = None


    def test_POINTER_c_wchar_arg(self):
        func = testdll._testfunc_p_p
        func.restype = c_wchar_p
        func.argtypes = POINTER(c_wchar),

        self.assertEqual(None, func(None))
        self.assertEqual("123", func("123"))
        self.assertEqual(None, func(c_wchar_p(None)))
        self.assertEqual("123", func(c_wchar_p("123")))

        self.assertEqual("123", func(c_wbuffer("123")))
        ca = c_wchar("a")
        self.assertEqual("a", func(pointer(ca))[0])
        self.assertEqual("a", func(byref(ca))[0])

    def test_c_wchar_p_arg(self):
        func = testdll._testfunc_p_p
        func.restype = c_wchar_p
        func.argtypes = c_wchar_p,

        c_wchar_p.from_param("123")

        self.assertEqual(None, func(None))
        self.assertEqual("123", func("123"))
        self.assertEqual(None, func(c_wchar_p(None)))
        self.assertEqual("123", func(c_wchar_p("123")))

        
        self.assertEqual("123", func(c_wbuffer("123")))
        ca = c_wchar("a")
        self.assertEqual("a", func(pointer(ca))[0])
        self.assertEqual("a", func(byref(ca))[0])


class ArrayTest(unittest.TestCase):
    def test(self):
        func = testdll._testfunc_ai8
        func.restype = POINTER(c_int)
        func.argtypes = c_int * 8,

        func((c_int * 8)(1, 2, 3, 4, 5, 6, 7, 8))

        

        def func(): pass
        CFUNCTYPE(None, c_int * 3)(func)


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