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

Antoine Pitrou solipsis at pitrou.net
Wed Jul 24 23:57:33 CEST 2013

On Wed, 24 Jul 2013 10:56:05 -0700 Guido van Rossum <guido at python.org> wrote:

But I'm also ready to propose that all this is such a mess that we should change the default fd/handle inheritance to False, *across platforms*, and damn the torpedoes -- i.e. accept breaking all existing 3rd party UNIX code for subprocess creation that bypasses the subprocess module, as well as breaking uses of os.spawn*() on both platforms that depend on FD inheritance beyond stdin/stdout/stderr).

So I suppose you mean "change it to False except for stdin/stdout/stderr"?

With the new, sane default, all we need instead of PEP 446 is a way to make an FD inheritable after it's been created, which can be a single os.makeinheritable(fd) call that you must apply to the fileno() of the stream or socket object you want inherited (or directly to a FD you created otherwise, e.g. with os.pipe()). On Windows, this should probably only work with os.spawn*(), since otherwise you need handle inheritance, not FD inheritance, and that's a non-portable concept anyway.

I'm not sure how fd inheritance could work without handle inheritance. (since a fd seems to just be a proxy for a handle)

To reduce the need for 3rd party subprocess creation code, we should have better daemon creation code in the stdlib -- I wrote some damn robust code for this purpose in my previous job, but it never saw the light of day.

What do you call "daemon"? An actual Unix-like daemon?

Regards

Antoine.

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