2012/2/18 Stefan Behnel <stefan...@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
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