Attached bug.py does crash *randomly* on AArch64. The code is extract from ctypes.test.test_as_parameter.AsParamPropertyWrapperTestCase.test_callbacks test.

Example with Python 2.7.15 and Python 3.6.8 on RHEL8:

# python2 bug.py
Illegal instruction (core dumped)
[root@cav-thunderx2s-cn88xx-01 ~]# python3 bug.py
...
OK
[root@cav-thunderx2s-cn88xx-01 ~]# python3 bug.py
Illegal instruction (core dumped)

I can reproduce the crash on Python 2.7.16rc compiled manually:
./configure --enable-unicode=ucs4 --with-system-ffi && make

RHEL8 currently uses libffi-3.1-18.el8.aarch64.

(I tried optimization levels -O0, -O1, -O2, -O3: I am always able to *randomly* trigger the crash.)

Original bug report, Python 2 crash on RHEL8:
https://bugzilla.redhat.com/show_bug.cgi?id=1652930

--

I don't know if it's related but I also saw the following error which has been reported in bpo-30991.

FAIL: test_pass_by_value (ctypes.test.test_structures.StructureTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/root/src/python-3.6.2/Lib/ctypes/test/test_structures.py", line 416, in test_pass_by_value
    self.assertEqual(s.first, 0xdeadbeef)
AssertionError: 195948557 != 3735928559