With the current state of gevent on 3.12b3 (gevent 23.7.0, greenlet 3.0a1), test__util.py crashes the interpreter while executing pure-Python code that calls traceback.format_stack(). This test exercises the format_run_info function, which looks for any reachable greenlet objects (using gc.get_objects()) and prints their stacks, starting with the greenlet.gr_frame frame object.

The crash happens when the traceback code executes f = f.f_back, and the crash is inside PyObject_GetAttr.

This suggests that the frame object is invalid or corrupted, which in turn suggests a greenlet issue, but:

1. All the other tests for gevent and greenlet pass, so greenlets and frame switching are working; and
2. Only some greenlets cause this error. Most of them print fine.

Perhaps gc.get_objects is finding greenlets that it shouldn't? Perhaps greenlet needs to be more proactive about setting gr_frame to None?

This has been observed on macOS.

On Linux, instead of crashing, f = f.f_back was producing an AttributeError: dict has no attribute f_back. Not sure how that could happen either baring memory corruption of some sort.

(Windows is not yet testing 3.12, so I don't know what happens there.)

For the release of gevent 23.7.0, I have disabled stack traces for greenlets in util.GreenletTree.__render_tb as a workaround. This is not ideal, obviously.