[Python-Dev] Inherance of file descriptor and handles on Windows (PEP 446) (original) (raw)

Victor Stinner victor.stinner at gmail.com
Wed Jul 24 23:50:08 CEST 2013

2013/7/24 Richard Oudkerk <shibturn at gmail.com>:

Wow. Indeed you can -- I just tested this myself. How is this accomplished? I guess the CRT has a backchannel to talk to itself when it creates a process using spawn*? CreateProcess() takes a STARTUPINFO argument with undocumented fields cbReserved2, lpReserved2. They are used to pass an array of fds.

So would it be possible to implement the pass_fds parameter of subprocess using spawnl() or the undocumented fields?

And is it possible to close all handles except one (implement "pass_handles")?

The idea would be to use something subprocess.Popen(cmd, pass_fds=[pipe_rfd], close_fds=True) or subprocess.Popen(cmd, pass_handles=[pipe_rhandle], close_handles=True) instead of subprocess.Popen(cmd, close_fds=False).

In the experimental branch of multiprocessing, child processes no longer inherit unnecessary handles.

Where is this branch? How did you create the channel between the manager and the worker?

Victor

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