[Python-Dev] PyWeakref_GetObject() borrows its reference from... whom?

[Chris Angelico]

On Mon, Oct 10, 2016 at 8:35 PM, Larry Hastings <larry at hastings.org> wrote:
> Huh?  In all other circumstances, a "borrowed" reference is exactly that: X
> has a reference, and you are relying on X's reference to keep the object
> alive.  Borrowing from a borrowed reference is simply a chain of these; Z
> borrows from Y, Y borrows from X, and X is the original person who did the
> incref.  But you're borrowing from something specific, somebody who the API
> guarantees has a legitimate reference on the object and won't drop it while
> you're using it.  I bet for every other spot in the API I can tell you from
> whom you're borrowing the reference.

Okay. Here's a test:

PyObject* PyList_GetItem(PyObject *list, Py_ssize_t index)
Return value: Borrowed reference.

Presumably you own a reference to the list itself before you call
this, and the list has a reference to its items. But suppose another
thread clear()s the list immediately after you call this; whose
reference are you borrowing now? The list's is gone.

Or is this another API that will have to change post gilectomy?

ChrisA