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bpo-35182: fix communicate() crash after child closes its pipes #18117

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Merged
gpshead merged 1 commit into from
Jan 22, 2020
Merged

bpo-35182: fix communicate() crash after child closes its pipes #18117

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4 changes: 2 additions & 2 deletions Lib/subprocess.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1983,9 +1983,9 @@ def _communicate(self, input, endtime, orig_timeout):
with _PopenSelector() as selector:
if self.stdin and input:
selector.register(self.stdin, selectors.EVENT_WRITE)
if self.stdout:
if self.stdout and not self.stdout.closed:
selector.register(self.stdout, selectors.EVENT_READ)
if self.stderr:
if self.stderr and not self.stderr.closed:
selector.register(self.stderr, selectors.EVENT_READ)

while selector.get_map():
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11 changes: 11 additions & 0 deletions Lib/test/test_subprocess.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3145,6 +3145,17 @@ def test_send_signal_race(self):
# so Popen failed to read it and uses a default returncode instead.
self.assertIsNotNone(proc.returncode)

def test_communicate_repeated_call_after_stdout_close(self):
proc = subprocess.Popen([sys.executable, '-c',
'import os, time; os.close(1), time.sleep(2)'],
stdout=subprocess.PIPE)
while True:
try:
proc.communicate(timeout=0.1)
return
except subprocess.TimeoutExpired:
pass


@unittest.skipUnless(mswindows, "Windows specific tests")
class Win32ProcessTestCase(BaseTestCase):
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2019-10-31-19-23-25.bpo-35182.hzeNl9.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fixed :func:`Popen.communicate` subsequent call crash when the child process
has already closed any piped standard stream, but still continues to be
running. Patch by Andriy Maletsky.