Safely using the C API when Python might shut down

[pitrou (Antoine Pitrou)]

@colesbury

what will you do if PyGILState_EnsureOrSafelyFail() returns an error code indicating failure? How are you going to handle that?

It depends on the situation. If I take the example from A new API for ensuring/releasing thread states - #20 by pitrou, I would return a C++ error reflecting the fact that the IO call failed. It’s quite natural and will allow C++ resources to clean up.

@colesbury

Furthermore, we can’t reliably pass an error up because we’re sometimes in situations where C++ calls into Python, which calls back into C++, which calls into Python:

C++ -> Python -> C++ -> Python
                    [^^ PyGILState_EnsureOrSafelyFail() fails here]

That sounds unlikely, no? If you’re being called synchronously from Python, why would PyGILState_EnsureOrSafelyFail not succeed?

In any case, it’s possible to return an error to the calling Python frame.