[ARROW-6157] [Python][C++] UnionArray with invalid data passes validation / leads to segfaults

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.16.0
• Component/s: C++, Python
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/22550
• Assignee: Antoine Pitrou
• Reporter: Joris Van den Bossche
• Created: 07/Aug/19 10:30
• Updated: 11/Jan/23 07:45
• Resolved: 29/Nov/19 10:40

Description

From the Python side, you can create an "invalid" UnionArray:

binary = pa.array([b'a', b'b', b'c', b'd'], type='binary') 
int64 = pa.array([1, 2, 3], type='int64') 
types = pa.array([0, 1, 0, 0, 2, 1, 0], type='int8')   # <- value of 2 is out of bound for number of childs
value_offsets = pa.array([0, 0, 2, 1, 1, 2, 3], type='int32')

a = pa.UnionArray.from_dense(types, value_offsets, [binary, int64])

Eg on conversion to python this leads to a segfault:

In [7]: a.to_pylist()
Segmentation fault (core dumped)

On the other hand, doing an explicit validation does not give an error:

In [8]: a.validate()

Should the validation raise errors for this case? (the C++ ValidateVisitor for UnionArray does nothing)

(so that this can be called from the Python API to avoid creating invalid arrays / segfaults there)

Issue Links

• links to: GitHub Pull Request #5892