Would it be possible to use a "struct _gc_runtime_state *state" variable instead?

struct _gc_runtime_state *state = &_PyInterpreterState_GET_UNSAFE()->gc;

If the line is too lone, maybe add a GET_STATE() macro which returns &_PyInterpreterState_GET_UNSAFE()->gc.

Same comment for the whole file. I would prefer to avoid introducing "PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE(); " lines if it's only used to get the GC state.