gh-152666: Avoid reference counting of code objects

[brijkapadia]

Functions keep a list of past code objects so that a frame only needs borrowed references to them.

• Issue: Avoid refcounting on code objects during frame creation/destruction #152666

[markshannon]

The implementation of the old codes list looks good.
I'm wondering if the behavior, not the implementation, could be tested (or is it already?)

Also, can you make f_executable a PyObject * and always borrow it, to minimize overhead?

[bedevere-app]

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[brijkapadia]

I have made the requested changes; please review again

Unless I'm missing something (which is possible!) I do not think there is a way for generators to hold borrowed references without changing behavior.

[bedevere-app]

Thanks for making the requested changes!

@markshannon: please review the changes made to this pull request.

[markshannon]

Unless I'm missing something (which is possible!) I do not think there is a way for generators to hold borrowed references without changing behavior.

The generator is no different to the frame: it can borrow the reference to the code object, as long as it has a strong reference to the function. As the generator needs to keep a reference to the code object when cleared, it must also keep a reference to the function.