Method test_is_alive_after_fork

Lib/test/test_threading.py:734–754

(self)

    @skip_unless_reliable_fork
    def test_is_alive_after_fork(self):
        # Try hard to trigger #18418: is_alive() could sometimes be True on
        # threads that vanished after a fork.
        old_interval = sys.getswitchinterval()
        self.addCleanup(sys.setswitchinterval, old_interval)

        # Make the bug more likely to manifest.
        test.support.setswitchinterval(1e-6)

        for i in range(20):
            t = threading.Thread(target=lambda: None)
            t.start()
            # Ignore the warning about fork with threads.
            with warnings.catch_warnings(category=DeprecationWarning,
                                         action="ignore"):
                if (pid := os.fork()) == 0:
                    os._exit(11 if t.is_alive() else 10)
                else:
                    t.join()

                    support.wait_process(pid, exitcode=10)

    def test_main_thread(self):
        main = threading.main_thread()