diff --git a/Lib/multiprocessing/popen_fork.py b/Lib/multiprocessing/popen_fork.py index 5d0fa569f12eaa..6396db45b136b6 100644 --- a/Lib/multiprocessing/popen_fork.py +++ b/Lib/multiprocessing/popen_fork.py @@ -14,14 +14,7 @@ class Popen(object): method = 'fork' def __init__(self, process_obj): - try: - sys.stdout.flush() - except (AttributeError, ValueError): - pass - try: - sys.stderr.flush() - except (AttributeError, ValueError): - pass + util._flush_std_streams() self.returncode = None self._launch(process_obj) diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py index 1d26b5e521e7e7..c6157b6046a0a6 100644 --- a/Lib/multiprocessing/process.py +++ b/Lib/multiprocessing/process.py @@ -274,8 +274,7 @@ def _bootstrap(self): traceback.print_exc() finally: util.info('process exiting with exitcode %d' % exitcode) - sys.stdout.flush() - sys.stderr.flush() + util._flush_std_streams() return exitcode diff --git a/Lib/multiprocessing/util.py b/Lib/multiprocessing/util.py index b490caa7e64333..24573764fab16a 100644 --- a/Lib/multiprocessing/util.py +++ b/Lib/multiprocessing/util.py @@ -388,6 +388,20 @@ def _close_stdin(): except (OSError, ValueError): pass +# +# Flush standard streams, if any +# + +def _flush_std_streams(): + try: + sys.stdout.flush() + except (AttributeError, ValueError): + pass + try: + sys.stderr.flush() + except (AttributeError, ValueError): + pass + # # Start a program with only specified fds kept open # diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py index e4d60f8804269d..dd0a9d7a862a46 100644 --- a/Lib/test/_test_multiprocessing.py +++ b/Lib/test/_test_multiprocessing.py @@ -427,10 +427,19 @@ def test_lose_target_ref(self): close_queue(q) @classmethod - def _test_error_on_stdio_flush(self, evt): + def _test_error_on_stdio_flush(self, evt, break_std_streams={}): + for stream_name, action in break_std_streams.items(): + if action == 'close': + stream = io.StringIO() + stream.close() + else: + assert action == 'remove' + stream = None + setattr(sys, stream_name, None) evt.set() - def test_error_on_stdio_flush(self): + def test_error_on_stdio_flush_1(self): + # Check that Process works with broken standard streams streams = [io.StringIO(), None] streams[0].close() for stream_name in ('stdout', 'stderr'): @@ -444,6 +453,24 @@ def test_error_on_stdio_flush(self): proc.start() proc.join() self.assertTrue(evt.is_set()) + self.assertEqual(proc.exitcode, 0) + finally: + setattr(sys, stream_name, old_stream) + + def test_error_on_stdio_flush_2(self): + # Same as test_error_on_stdio_flush_1(), but standard streams are + # broken by the child process + for stream_name in ('stdout', 'stderr'): + for action in ('close', 'remove'): + old_stream = getattr(sys, stream_name) + try: + evt = self.Event() + proc = self.Process(target=self._test_error_on_stdio_flush, + args=(evt, {stream_name: action})) + proc.start() + proc.join() + self.assertTrue(evt.is_set()) + self.assertEqual(proc.exitcode, 0) finally: setattr(sys, stream_name, old_stream) diff --git a/Misc/NEWS.d/next/Library/2018-03-11-19-03-52.bpo-31804.i8KUMp.rst b/Misc/NEWS.d/next/Library/2018-03-11-19-03-52.bpo-31804.i8KUMp.rst new file mode 100644 index 00000000000000..7fcede297aca31 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2018-03-11-19-03-52.bpo-31804.i8KUMp.rst @@ -0,0 +1,2 @@ +Avoid failing in multiprocessing.Process if the standard streams are closed +or None at exit.