2012/2/18 Stefan Behnel <stefan_ml@behnel.de>

I couldn't find the PyWeakref_LockObject() function anywhere. That's a
PyPy-only thing, right? I aliased it to (NULL) when compiling for CPython.

Yes, this function is PyPy-only, to fix a flaw of PyWeakref_GetObject:

it returns a borrowed reference, which is very dangerous because the object

can disappear anytime: with a garbage collection, or another thread...

Fortunately the GIL is here to protect you, but the only sane thing to do

is to quickly INCREF the returned reference.

PyWeakref_LockObject directly returns a new reference.

In PyPy, the behavior of PyWeakref_GetObject is even worse:

to avoid returning a refcount of zero, the returned reference is attached

to the weakref, effectively turning it into a strong reference!

I now realize that this was written before we implemented the

"temporary container" for borrowed references: PyWeakref_GetObject()

could return a reference valid for the duration of the current C call.

--
Amaury Forgeot d'Arc