Vinay Sajip added the comment:
When adding the fix for #20160 I had added a test involving passing a struct by
value to a Python callback. I modified that test to update the struct in the
callback, and check that the passed-in struct hadn't changed.
def test_callback_large_struct(self):
class Check: pass
class X(Structure):
_fields_ = [
('first', c_ulong),
('second', c_ulong),
('third', c_ulong),
]
def callback(check, s):
check.first = s.first
check.second = s.second
check.third = s.third
# See issue #29565.
# The structure should be passed by value, so
# any changes to it should not be reflected in
# the value passed
s.first = s.second = s.third = 0x0badf00d
check = Check()
s = X()
s.first = 0xdeadbeef
s.second = 0xcafebabe
s.third = 0x0bad1dea
CALLBACK = CFUNCTYPE(None, X)
dll = CDLL(_ctypes_test.__file__)
func = dll._testfunc_cbk_large_struct
func.argtypes = (X, CALLBACK)
func.restype = None
# the function just calls the callback with the passed structure
func(s, CALLBACK(functools.partial(callback, check)))
self.assertEqual(check.first, s.first)
self.assertEqual(check.second, s.second)
self.assertEqual(check.third, s.third)
self.assertEqual(check.first, 0xdeadbeef)
self.assertEqual(check.second, 0xcafebabe)
self.assertEqual(check.third, 0x0bad1dea)
# See issue #29565.
# Ensure that the original struct is unchanged.
self.assertEqual(s.first, check.first)
self.assertEqual(s.second, check.second)
self.assertEqual(s.third, check.third)
The changed test still passes, so it looks like ctypes makes a copy when
passing from C to a Python callback, but not when passing from Python to C.
----------
_______________________________________
Python tracker <[email protected]>
<http://bugs.python.org/issue29565>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
