Method test_refcount_errors

Lib/test/test_gc.py:1389–1442

(self)

    @unittest.skipIf(BUILD_WITH_NDEBUG,
                     'built with -NDEBUG')
    def test_refcount_errors(self):
        self.preclean()
        # Verify the "handling" of objects with broken refcounts

        # Skip the test if ctypes is not available
        import_module("ctypes")

        import subprocess
        code = textwrap.dedent('''
            from test.support import gc_collect, SuppressCrashReport

            a = [1, 2, 3]
            b = [a, a]
            a.append(b)

            # Avoid coredump when Py_FatalError() calls abort()
            SuppressCrashReport().__enter__()

            # Simulate the refcount of "a" being too low (compared to the
            # references held on it by live data), but keeping it above zero
            # (to avoid deallocating it):
            import ctypes
            ctypes.pythonapi.Py_DecRef(ctypes.py_object(a))
            del a
            del b

            # The garbage collector should now have a fatal error
            # when it reaches the broken object
            gc_collect()
        ''')
        p = subprocess.Popen([sys.executable, "-c", code],
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE)
        stdout, stderr = p.communicate()
        p.stdout.close()
        p.stderr.close()
        # Verify that stderr has a useful error message:
        self.assertRegex(stderr,
            br'gc.*\.c:[0-9]+: .*: Assertion "gc_get_refs\(.+\) .*" failed.')
        self.assertRegex(stderr,
            br'refcount is too small')
        # "address : 0x7fb5062efc18"
        # "address : 7FB5062EFC18"
        address_regex = br'[0-9a-fA-Fx]+'
        self.assertRegex(stderr,
            br'object address  : ' + address_regex)
        self.assertRegex(stderr,
            br'object refcount : 1')
        self.assertRegex(stderr,
            br'object type     : ' + address_regex)
        self.assertRegex(stderr,
            br'object type name: list')
        self.assertRegex(stderr,
            br'object repr     : \[1, 2, 3, \[\[...\], \[...\]\]\]')


class GCTogglingTests(unittest.TestCase):