[ARROW-4018] [C++] RLE decoder may not big-endian compatible

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.11.1
• Fix Version/s: 1.0.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20620
• Assignee: Kazuaki Ishizaki
• Reporter: Antoine Pitrou
• Created: 13/Dec/18 13:07
• Updated: 11/Jan/23 07:31
• Resolved: 11/May/20 13:20

Description

This issue was found by Coverity. The RleDecoder::NextCounts method has the following code to fetch the repeated literal in repeated runs:

    bool result =
        bit_reader_.GetAligned<T>(static_cast<int>(BitUtil::CeilDiv(bit_width_, 8)),
                                  reinterpret_cast<T*>(&current_value_));

Coverity says this:

Pointer "&this->current_value_" points to an object whose effective type is "unsigned long long" (64 bits, unsigned) but is dereferenced as a narrower "unsigned int" (32 bits, unsigned). This may lead to unexpected results depending on machine endianness.

In addition, it's not obvious whether current_value_ also needs byte-swapping (presumably, at least in the Parquet file format, it's supposed to be stored in little-endian format in the RLE bitstream).

Issue Links

• links to: GitHub Pull Request #7144