wtf cffi

test_to_cffi.py

import weakref
from xcffib.ffi import bytes_to_cdata, ffi
global_weakkeydict = weakref.WeakKeyDictionary()

def test_to_cffi():
    c_key = ffi.new("struct xcb_extension_t *")
    c_key.name = name = bytes_to_cdata(b"testing")

    c_key_ref = weakref.ref(c_key)
    name_ref = weakref.ref(name)

    return c_key, c_key_ref, name_ref


def test_to_cffi2():
    c_key = ffi.new("struct xcb_extension_t *")
    c_key.name = name = bytes_to_cdata(b"testing2")

    global_weakkeydict[c_key] = name

    c_key_ref = weakref.ref(c_key)
    name_ref = weakref.ref(name)

    return c_key, c_key_ref, name_ref

k, kr, nr = test_to_cffi()
k2, kr2, nr2 = test_to_cffi2()

import gc
gc.collect()

assert kr() is not None
assert nr() is None # We don't want this to be None, but it is
assert ffi.string(k.name) != b'testing' # As a result we lose the name variable

assert kr2() is not None
assert nr2() is not None # Now the reference sticks around
assert ffi.string(k2.name) == b'testing2' # Now the name variable doesn't change