The PEP 446 was implemented in Python 3.4. All file descriptors are now created non inheritable. The implementation was not finished on Windows, handles may be created inheritable. The Python code should be audoted for that.

For example, hCryptProv in Python/random.c is inheritable or not?

On Windows, handles are created non-inheritable by default, but I would prefer to double check.

The tool "Handle" can be used to list all open handles of a process:
http://technet.microsoft.com/en-us/sysinternals/bb896655.aspx

To test that all handles are non-inheritable: run all Python unit tests, create a subprocesss with close_fds=False, list open handles of the child process and check that the list of not longer than a fresh Python process.

> For example, hCryptProv in Python/random.c is inheritable or not?

This is not a standard handle. GetHandleInformation() fails with a Windows error 6 (invalid descriptor).

I listed inheritable handles with a loop on range(0, 0x1001): only handles of stdin, stdout and stderr are inheritable. The other handles are not inheritable.

I also listed handles of parent and child processes using "handle.exe" tool from Microsoft. I see that the child has less open handle, all file handles that I opened manually are not inheried, and everything looks fine.

So I think that the issue can now be closed.