Trying to robustly patch func.__globals__

[jgarvin (Joseph Garvin)]

@blhsing

However, we can work around it by creating a new types.FunctionType object with all the same attribute values except globals, which we can replace with an object of a dict subclass that per your example records what global lookups occur.

Sorry yeah I spoke imprecisely, that is exactly what I did originally when I was doing a pure python module. In C nothing prevents reassigning func->func_globals although I’m not sure how kosher this is. Since I do it from PyFunction_AddWatcher callback as soon as the function is created I think there’s no time for any other python code to observe the difference.

@blhsing

That is true for updates but untrue for lookups. The Python interpreter has this strange asymmetry where lookups to globals would fall back to a slow path of PyMapping_* calls for an object of a dict subclass

Yep I also posted about that shortly after this

@blhsing

Knowing the above, this approach can actually work if we simply update func.__globals__ with the new content after a call

This is an interesting idea. I think you can probably break it even within one thread though, because you could call other functions before you return that might expect to see changes in globals right away.