QUERY · ISSUE

Taking slice of memoryview in Viper function crashes PyBoard

openby twisteroidambassadoropened 2020-10-07updated 2025-07-02

bugpy-core

On a PyBoard v1.1 with firmware 1.13, put the following code into a file:

import micropython


@micropython.viper
def take_memoryview_slice():
    ba = bytearray(10)
    mv = memoryview(ba)
    slice = mv[0:1]

Running take_memoryview_slice() resets the PyBoard.

CANDIDATE · ISSUE

Resizing bytearray with active memoryviews corrupts state and segfaults

openby MaksimFengopened 2025-09-29updated 2025-10-20

bug

Port, board and/or hardware

Unix

MicroPython version

MicroPython v1.27.0-preview.107.gd1607598f on 2025-09-09; linux [GCC 14.2.0] version

Reproduction

import gc

ba = bytearray(b"abcdefghij")
views = [memoryview(ba) for _ in range(4)]

ba[:] = ba + b"X"*256   

gc.collect()            

for i, mv in enumerate(views):
    mv[0:1] = b"Y"

Expected behaviour

Attempting to resize a bytearray that has active memoryview exports should raise a Python exception and must not corrupt the VM or crash.

Observed behaviour

The resize succeeds; existing memoryviews retain stale pointers to the old buffer. After gc.collect() (or later operations), the VM state gets corrupted and the process segfaults in unrelated code paths (e.g., during enumerate, inside mp_load_method_maybe).

Additional Information

No, I've provided everything above.

Code of Conduct

Yes, I agree