QUERY · ISSUE

bytearray(length) does not validate length is >= 0

openby dhalbertopened 2021-08-26updated 2021-08-28

py-core

>>> bytearray(-1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
MemoryError: memory allocation failed, allocating 4294967295 bytes

This is pretty minor, since it does raise an error. CPython raises a ValueError instead:

>>> bytearray(-1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: negative count

CANDIDATE · ISSUE

Unix: CPython incompatibility assigning negative values to bytearrays.

openby peterhinchopened 2017-07-09updated 2025-04-04

py-core

This is arguably minor, but I thought it worth flagging up. It also applies to bytes objects.

MicroPython v1.8.7-893-g46b849a on 2017-06-22; linux version
Use Ctrl-D to exit, Ctrl-E for paste mode
>>> a = bytearray([0, 1, -1])
>>> a[2]
255
>>>

Under CPython 3.4.3:

>>> a = bytearray([0, 1, -1])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: byte must be in range(0, 256)

Assessment

Q Qwen · high

Both issues concern CPython compatibility problems with bytearray validation in MicroPython, but they address different specific bugs. Issue #7712 is about the bytearray() constructor not validating that the length argument is non-negative (raising MemoryError instead of ValueError for negative length). Issue #3204 is about bytearray/bytes initialization not validating that individual byte values are in the valid range (0-255), accepting negative values and wrapping them instead of raising ValueError. These are distinct validation issues in different parts of the bytearray implementation.

Suggested action

Keep both issues open as they address different validation problems. The fix for #7712 (constructor length validation) does not resolve #3204 (element value range validation).

bytearray(length) does not validate length is >= 0

Unix: CPython incompatibility assigning negative values to bytearrays.

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