Python bug affecting PyTools/PyCUDA on Windows - invalid handle when piping stdout from subprocess
by Boswell, Dan - GT&O JPN-MLJS
There's a bug in python (http://bugs.python.org/issue3905) that affects PyTools when PyCUDA creates a subprocess to run nvcc. Fortunately this is only the case for Windows machines, and specifically when PyCUDA is run in a UI application (shell) which itself is run from the console; something that's probably not very common. Unfortunately for me, that is _exactly_ the scenario for the IDE/shell that we use where I work (Windows XP, Python 2.6.5).
Although the python bug remains open, there's a simple workaround which involves passing subprocess.PIPE as the argument to _all_ the std* keywords when using subprocess.Popen in prefork.py. I've attached a patch, but let me know if this is not the correct forum to do so, or if there's an alternative process (e.g. a git pull request).
One simple way of reproducing this is to use IDLE:
1. From the Windows console run 'pythonw idlelib\idle.pyw -n', then in IDLE:
>>> # This fails
>>> from subprocess import Popen, PIPE
>>> Popen(['nvcc', '--version'], stdout=PIPE)
>>> # This works
>>> Popen(['nvcc', '--version'], stdin=PIPE, stdout=PIPE, stderr=PIPE)
2. Or run hello_gpu.py in that IDLE window
And you should get an error like the following
File "C:\home\dbo\argh\ext\win32_vc9\lib\python2.6\subprocess.py", line 773, in _make_inheritable
WindowsError: [Error 6] The handle is invalid
Hope that helps, and it would be good to get this into the official PyTools repo/distribution so that we don't have to maintain a patched version here! :)
Risk Technology, BoAML
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