Found libffi PR240 that fixes closures on Android:

shell@ASUS_Z00E_2:/data/local/tmp $ python3.6 -m test.test_ctypes
...................................................................s......s..............s....................ssssssssssssssssssssss..................................ssssssssssssssssssssssssssss.s...sssOpenGL libraries:
         ('GL', None)
         ('GLU', None)
         ('gle', None)
sss...........................s.s............s.........libc_name is None
ss.sssss...s...s...........s....s..................................................................s.................................sssss..ss..........................s....................ss.sssssss
----------------------------------------------------------------------
Ran 456 tests in 2.090s

OK (skipped=92)

See https://github.com/yan12125/python3-android/commit/1daebca128e9ca1a9a39ef143ded7090cfa71cc9 for details.

By http://comments.gmane.org/gmane.comp.lib.ffi.general/1235, SELinux affects the result, too. PR240 of libffi assumes SELinux is disabled. I have disabled SELinux on my phone for some root applications. I'm not sure whether PR240 works for phones with SELinux or not.