I noticed a memory leak in the usage of native mpy files.

Even for the simple example given in the documentation the following code demonstrates the issue:

import factorial
from urandom import randint
import gc

for i in range(100000):
    c = factorial.factorial(randint(4, 15))
    print(gc.mem_free())
    print(i, c)

I tested this with

MicroPython v1.12 on 2019-12-20; PYBD-SF2W with STM32F722IEK

on a Pyboad D-series.