gh-139653: If platform API doesn't give the current stack, use generic fallback by encukou · Pull Request #139667 · python/cpython

Fall back to _Py_get_machine_stack_pointer if platform-specific API doesn't give us a stack that we're currently in. This might happen if some bespoke stack switching mechanism is in use.

With this, gh-139653 should be solved if the user calls _Py_InitializeRecursionLimits after each jump_fcontext.