[Python-checkins] bpo-31804: Fix multiprocessing.Process with broken standard streams (#6079)
Antoine Pitrou
webhook-mailer at python.org
Sun Mar 11 14:21:41 EDT 2018
https://github.com/python/cpython/commit/e756f66c83786ee82f5f7d45931ae50a6931dd7f
commit: e756f66c83786ee82f5f7d45931ae50a6931dd7f
branch: master
author: Antoine Pitrou <pitrou at free.fr>
committer: GitHub <noreply at github.com>
date: 2018-03-11T19:21:38+01:00
summary:
bpo-31804: Fix multiprocessing.Process with broken standard streams (#6079)
In some conditions the standard streams will be None or closed in the child process (for example if using "pythonw" instead of "python" on Windows). Avoid failing with a non-0 exit code in those conditions.
Report and initial patch by poxthegreat.
files:
A Misc/NEWS.d/next/Library/2018-03-11-19-03-52.bpo-31804.i8KUMp.rst
M Lib/multiprocessing/popen_fork.py
M Lib/multiprocessing/process.py
M Lib/multiprocessing/util.py
M Lib/test/_test_multiprocessing.py
diff --git a/Lib/multiprocessing/popen_fork.py b/Lib/multiprocessing/popen_fork.py
index b0fc01396eb2..008b97b36628 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.finalizer = None
self._launch(process_obj)
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
index 8fff3e105ead..cd592d0bdf09 100644
--- a/Lib/multiprocessing/process.py
+++ b/Lib/multiprocessing/process.py
@@ -314,8 +314,7 @@ def _bootstrap(self):
finally:
threading._shutdown()
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 f0827f0a9693..0c4eb2473273 100644
--- a/Lib/multiprocessing/util.py
+++ b/Lib/multiprocessing/util.py
@@ -391,6 +391,20 @@ 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 1e497a572a76..940fe584e752 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -584,10 +584,19 @@ def test_wait_for_threads(self):
self.assertTrue(evt.is_set())
@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'):
@@ -601,6 +610,24 @@ 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 000000000000..7fcede297aca
--- /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.
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