On my FreeBSD 12.0-RELEASE-p10 VM, test_threading.test_recursion_limit() does crash with SIGSEGV and create a coredump.

vstinner@freebsd$ ./python -m test -v test_threading -m test_recursion_limit
== CPython 3.9.0a0 (heads/master:e0b6117e27, Aug 21 2019, 12:23:28) [Clang 6.0.1 (tags/RELEASE_601/final 335540)]
== FreeBSD-12.0-RELEASE-p10-amd64-64bit-ELF little-endian
== cwd: /usr/home/vstinner/python/master/build/test_python_3547
== CPU count: 2
== encodings: locale=UTF-8, FS=utf-8
Run tests sequentially
0:00:01 load avg: 4.85 [1/1] test_threading
test_recursion_limit (test.test_threading.ThreadingExceptionTests) ... FAIL

======================================================================
FAIL: test_recursion_limit (test.test_threading.ThreadingExceptionTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/vstinner/python/master/Lib/test/test_threading.py", line 1086, in test_recursion_limit
    self.assertEqual(p.returncode, 0, "Unexpected error: " + stderr.decode())
AssertionError: -11 != 0 : Unexpected error: 

----------------------------------------------------------------------

Ran 1 test in 6.017s

FAILED (failures=1)
Warning -- files was modified by test_threading
  Before: []
  After:  ['python.core'] 
test test_threading failed
test_threading failed

== Tests result: FAILURE ==

1 test failed:
    test_threading

Total duration: 7 sec 284 ms
Tests result: FAILURE