[Python-Dev] PEP 446: Open issues/questions

[Charles-François Natali]

2013/8/2 Victor Stinner <victor.stinner at gmail.com>:
> On Windows, inheritable handles (including open files) are still
> inherited when a standard stream is overriden in the subprocess module
> (default value of close_fds is set to False in this case). This issue
> cannot be solved (at least, I don't see how): it is a limitation of
> Windows. bInheritedHandles must be set to FALSE (inherit *all*
> inheritable handles) when handles of standard streams are specified in
> the startup information of CreateProcess().

Then how about changing the default to creating file descriptors
unheritable on Windows (which is apparently the default)?
Then you can implement keep_fds by setting them inheritable right
before creation, and resetting them right after: sure there's a race
in a multi-threaded program, but AFAICT that's already the case right
now, and Windows API doesn't leave us any other choice.
Amusingly, they address this case by recommending putting process
creation in a critical section:
http://support.microsoft.com/kb/315939/en-us

This way, we keep default platform behavior on Unix and on Windows (so
user using low-level syscalls/APIs won't be surprised), and we have a
clean way to selectively inherit FD in child processes through
subprocess.

cf