bpo-42639: atexit._run_exitfuncs() uses sys.unraisablehook (GH-23779)

atexit._run_exitfuncs() now logs callback exceptions using
sys.unraisablehook, rather than logging them directly into
sys.stderr and raising the last exception.

Run GeneralTest of test_atexit in a subprocess since it calls
atexit._clear() which clears all atexit callbacks.

_PyAtExit_Fini() sets state->callbacks to NULL.

Lib/test/test_atexit.py

@@ -1,5 +1,4 @@
 import atexit
-import io
 import os
 import sys
 import textwrap
@@ -7,154 +6,14 @@ import unittest
 from test import support
 from test.support import script_helper
 
-### helpers
-def h1():
-    print("h1")
-
-def h2():
-    print("h2")
-
-def h3():
-    print("h3")
-
-def h4(*args, **kwargs):
-    print("h4", args, kwargs)
-
-def raise1():
-    raise TypeError
-
-def raise2():
-    raise SystemError
-
-def exit():
-    raise SystemExit
-
 
 class GeneralTest(unittest.TestCase):
+    def test_general(self):
+        # Run _test_atexit.py in a subprocess since it calls atexit._clear()
+        script = support.findfile("_test_atexit.py")
+        script_helper.run_test_script(script)
 
-    def setUp(self):
-        self.save_stdout = sys.stdout
-        self.save_stderr = sys.stderr
-        self.stream = io.StringIO()
-        sys.stdout = sys.stderr = self.stream
-        atexit._clear()
-
-    def tearDown(self):
-        sys.stdout = self.save_stdout
-        sys.stderr = self.save_stderr
-        atexit._clear()
-
-    def test_args(self):
-        # be sure args are handled properly
-        atexit.register(h1)
-        atexit.register(h4)
-        atexit.register(h4, 4, kw="abc")
-        atexit._run_exitfuncs()
-
-        self.assertEqual(self.stream.getvalue(),
-                            "h4 (4,) {'kw': 'abc'}\nh4 () {}\nh1\n")
-
-    def test_badargs(self):
-        atexit.register(lambda: 1, 0, 0, (x for x in (1,2)), 0, 0)
-        self.assertRaises(TypeError, atexit._run_exitfuncs)
-
-    def test_order(self):
-        # be sure handlers are executed in reverse order
-        atexit.register(h1)
-        atexit.register(h2)
-        atexit.register(h3)
-        atexit._run_exitfuncs()
-
-        self.assertEqual(self.stream.getvalue(), "h3\nh2\nh1\n")
-
-    def test_raise(self):
-        # be sure raises are handled properly
-        atexit.register(raise1)
-        atexit.register(raise2)
-
-        self.assertRaises(TypeError, atexit._run_exitfuncs)
-
-    def test_raise_unnormalized(self):
-        # Issue #10756: Make sure that an unnormalized exception is
-        # handled properly
-        atexit.register(lambda: 1 / 0)
-
-        self.assertRaises(ZeroDivisionError, atexit._run_exitfuncs)
-        self.assertIn("ZeroDivisionError", self.stream.getvalue())
-
-    def test_exit(self):
-        # be sure a SystemExit is handled properly
-        atexit.register(exit)
-
-        self.assertRaises(SystemExit, atexit._run_exitfuncs)
-        self.assertEqual(self.stream.getvalue(), '')
-
-    def test_print_tracebacks(self):
-        # Issue #18776: the tracebacks should be printed when errors occur.
-        def f():
-            1/0  # one
-        def g():
-            1/0  # two
-        def h():
-            1/0  # three
-        atexit.register(f)
-        atexit.register(g)
-        atexit.register(h)
-
-        self.assertRaises(ZeroDivisionError, atexit._run_exitfuncs)
-        stderr = self.stream.getvalue()
-        self.assertEqual(stderr.count("ZeroDivisionError"), 3)
-        self.assertIn("# one", stderr)
-        self.assertIn("# two", stderr)
-        self.assertIn("# three", stderr)
-
-    def test_stress(self):
-        a = [0]
-        def inc():
-            a[0] += 1
-
-        for i in range(128):
-            atexit.register(inc)
-        atexit._run_exitfuncs()
-
-        self.assertEqual(a[0], 128)
-
-    def test_clear(self):
-        a = [0]
-        def inc():
-            a[0] += 1
-
-        atexit.register(inc)
-        atexit._clear()
-        atexit._run_exitfuncs()
-
-        self.assertEqual(a[0], 0)
-
-    def test_unregister(self):
-        a = [0]
-        def inc():
-            a[0] += 1
-        def dec():
-            a[0] -= 1
-
-        for i in range(4):
-            atexit.register(inc)
-        atexit.register(dec)
-        atexit.unregister(inc)
-        atexit._run_exitfuncs()
-
-        self.assertEqual(a[0], -1)
-
-    def test_bound_methods(self):
-        l = []
-        atexit.register(l.append, 5)
-        atexit._run_exitfuncs()
-        self.assertEqual(l, [5])
-
-        atexit.unregister(l.append)
-        atexit._run_exitfuncs()
-        self.assertEqual(l, [5])
-
+class FunctionalTest(unittest.TestCase):
     def test_shutdown(self):
         # Actually test the shutdown mechanism in a subprocess
         code = textwrap.dedent("""