Lib/test/test_wait3.py

"""This test checks for correct wait3() behavior.
"""

import os
import subprocess
import sys
import time
import unittest
from test.fork_wait import ForkWait
from test import support

if not hasattr(os, 'fork'):
    raise unittest.SkipTest("os.fork not defined")

if not hasattr(os, 'wait3'):
    raise unittest.SkipTest("os.wait3 not defined")

class Wait3Test(ForkWait):
    def wait_impl(self, cpid, *, exitcode):
        # This many iterations can be required, since some previously run
        # tests (e.g. test_ctypes) could have spawned a lot of children
        # very quickly.
        deadline = time.monotonic() + support.SHORT_TIMEOUT
        while time.monotonic() <= deadline:
            # wait3() shouldn't hang, but some of the buildbots seem to hang
            # in the forking tests.  This is an attempt to fix the problem.
            spid, status, rusage = os.wait3(os.WNOHANG)
            if spid == cpid:
                break
            time.sleep(0.1)

        self.assertEqual(spid, cpid)
        self.assertEqual(status, exitcode << 8,
                         "cause = %d, exit = %d" % (status&0xff, status>>8))
        self.assertTrue(rusage)

    def test_wait3_rusage_initialized(self):
        # Ensure a successful wait3() call where no child was ready to report
        # its exit status does not return uninitialized memory in the rusage
        # structure. See bpo-36279.
        args = [sys.executable, '-c', 'import sys; sys.stdin.read()']
        proc = subprocess.Popen(args, stdin=subprocess.PIPE)
        try:
            pid, status, rusage = os.wait3(os.WNOHANG)
            self.assertEqual(0, pid)
            self.assertEqual(0, status)
            self.assertEqual(0, sum(rusage))
        finally:
            proc.stdin.close()
            proc.wait()


def tearDownModule():
    support.reap_children()

if __name__ == "__main__":
    unittest.main()