Issue #8780: Fix a regression introduced by r78946 in subprocess on Windows

Ensure that stdout / stderr is inherited from the parent if stdout=PIPE /
stderr=PIPE is not used.

2 files changed, 12 insertions, 1 deletions

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index adbee0b..ad6fd1f 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -843,7 +843,7 @@ class Popen(object):
             # Process startup details
             if startupinfo is None:
                 startupinfo = STARTUPINFO()
-            if None not in (p2cread, c2pwrite, errwrite):
+            if -1 not in (p2cread, c2pwrite, errwrite):
                 startupinfo.dwFlags |= _subprocess.STARTF_USESTDHANDLES
                 startupinfo.hStdInput = p2cread
                 startupinfo.hStdOutput = c2pwrite
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index 96c8ebf..0dd5da4 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -535,6 +535,17 @@ class ProcessTestCase(BaseTestCase):
             if c.exception.errno != 2:  # ignore "no such file"
                 raise c.exception
 
+    def test_issue8780(self):
+        # Ensure that stdout is inherited from the parent
+        # if stdout=PIPE is not used
+        code = ';'.join((
+            'import subprocess, sys',
+            'retcode = subprocess.call('
+                "[sys.executable, '-c', 'print(\"Hello World!\")'])",
+            'assert retcode == 0'))
+        output = subprocess.check_output([sys.executable, '-c', code])
+        self.assert_(output.startswith(b'Hello World!'), ascii(output))
+
 
 # context manager
 class _SuppressCoreFiles(object):