[Python] Numba cfunc factory with numpy arrays

I want to have a factory method that calls a cfunc using numpy arrays. I am trying to pass the numpy arrays by using a ctype pointer. Since my original code is rather complicated I have made a simple case that reproduces the error I am getting:

import numpy as np
from numba import cfunc, carray
from numba.types import intc, CPointer, float64
import ctypes

class SimpleExample():
def __init__(self,array):
self.array = array
self.n = array.size

# Define the C signature: double func(double *input_array, int n)
sig = float64(CPointer(float64), intc)
sig2 = float64()

@staticmethod
@cfunc(sig)
def sum_array(ptr, n):
arr = carray(ptr, n) # Convert raw pointer to NumPy array
return np.sum(arr)

def sum_factory(self):
arr = self.array
size = self.n
sum_fun = type(self).sum_array
arr_ptr = arr.ctypes.data_as(ctypes.POINTER(ctypes.c_double))
@cfunc(sig2)
def sum_array_2():
return sum_fun(arr_ptr,size)
return sum_array_2.address


a = np.array([1.0, 2.0, 3.0, 4.0], dtype=np.float64)
example = SimpleExample(a)

# Get pointer to factory-generated function
func_ptr = example.sum_factory()

# Create ctypes function pointer with no args (signature: double func())
cfunc_type = ctypes.CFUNCTYPE(ctypes.c_double)
cfunc_instance = cfunc_type(func_ptr)

print("Sum from SimplerExample sum_factory:", cfunc_instance())


This should produce the error:

KeyError Traceback (most recent call last)
File ".../numba/core/typing/bufproto.py", line 56, in decode_pep3118_format
return _pep3118_scalar_map[fmt.lstrip('=')]
KeyError: '&<d'

During handling of the above exception, another exception occurred:

NumbaValueError Traceback (most recent call last)
File "<ipython-input>", line 36, in <module>
func_ptr = example.sum_factory()
File "<ipython-input>", line 27, in sum_factory
arr_ptr = arr.ctypes.data_as(ctypes.POINTER(ctypes.c_double))
...
File ".../numba/core/typing/bufproto.py", line 58, in decode_pep3118_format
raise NumbaValueError("unsupported PEP 3118 format %r" % (fmt,))

NumbaValueError: Failed in nopython mode pipeline (step: nopython frontend)
Untyped global name 'arr_ptr': unsupported PEP 3118 format '&<d'
During: Pass nopython_type_inference

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