[ARROW-3790] [C++] Signed to unsigned integer cast yields incorrect results when type sizes are the same

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.12.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20160
• Assignee: Francois Saint-Jacques
• Reporter: Wes McKinney
• Created: 14/Nov/18 15:17
• Updated: 11/Jan/23 07:29
• Resolved: 27/Nov/18 22:16

Description

In https://github.com/apache/arrow/blob/master/cpp/src/arrow/compute/kernels/cast.cc#L239, an int32_t is overflows in

constexpr in_type kMax = static_cast<in_type>(std::numeric_limits<out_type>::max());

resulting in safety checks not being correctly performed

In [2]: arr = pa.array([-1, -2, -3], type='int32')

In [3]: arr.cast('uint32')
Out[3]: 
<pyarrow.lib.UInt32Array object at 0x7f4889457b88>
[
  4294967295,
  4294967294,
  4294967293
]

This would be expected to error when safe=True

Issue Links

• links to: GitHub Pull Request #3022