[Patches] [ python-Patches-1603907 ] subprocess: error redirecting i/o from non-console process
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Patches item #1603907, was opened at 2006-11-27 17:20
Message generated for change (Comment added) made by orenti
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Category: Library (Lib)
Group: Python 2.6
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Oren Tirosh (orenti)
Assigned to: Peter Åstrand (astrand)
Summary: subprocess: error redirecting i/o from non-console process
Initial Comment:
In IDLE, PythonWin or other non-console interactive Python under Windows:
>>> from subprocess import *
>>> Popen('cmd', stdout=PIPE)
Traceback (most recent call last):
File "<pyshell#11>", line 1, in -toplevel-
Popen('', stdout=PIPE)
File "C:\python24\lib\subprocess.py", line 533, in __init__
(p2cread, p2cwrite,
File "C:\python24\lib\subprocess.py", line 593, in _get_handles
p2cread = self._make_inheritable(p2cread)
File "C:\python24\lib\subprocess.py", line 634, in _make_inheritable
DUPLICATE_SAME_ACCESS)
TypeError: an integer is required
The same command in a console windows is successful.
Why it happens:
subprocess assumes that GetStdHandle always succeeds but when there is no console it returns None. DuplicateHandle then complains about getting a non-integer. This problem does not happen when redirecting all three standard handles.
Solution:
Replace None with -1 (INVALID_HANDLE_VALUE) in _make_inheritable.
Patch attached.
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>Comment By: Oren Tirosh (orenti)
Date: 2007-01-07 18:09
Message:
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If you duplicate INVALID_HANDLE_VALUE you get a new valid handle to
nothing :-) I guess the code really should not rely on this undocumented
behavior. The reason I didn't return INVALID_HANDLE_VALUE directly is
because DuplicateHandle returns a _subprocess_handle object, not an int.
It's expected to have a .Close() method elsewhere in the code.
Because of subtle difference between in the behavior of the _subprocess
and win32api implementations of GetStdHandle in this case solving this
issue this gets quite messy!
File Added: subprocess-noconsole2.patch
----------------------------------------------------------------------
Comment By: Peter Åstrand (astrand)
Date: 2007-01-07 10:58
Message:
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This patch looks very interesting. However, it feels a little bit strange
to call DuplicateHandle with a handle of -1. Is this really allowed? What
will DuplicateHandle return in this case? INVALID_HANDLE_VALUE? In that
case, isn't it better to return INVALID_HANDLE_VALUE directly?
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