[jira] [Commented] (ARROW-4018) [C++] RLE decoder may not big-endian compatible

[Antoine Pitrou (Jira)]

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https://issues.apache.org/jira/browse/ARROW-4018?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16931653#comment-16931653
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Antoine Pitrou commented on ARROW-4018:
---------------------------------------

Also [~emkornfi...@gmail.com]


> [C++] RLE decoder may not big-endian compatible
> -----------------------------------------------
>
>                 Key: ARROW-4018
>                 URL: https://issues.apache.org/jira/browse/ARROW-4018
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: C++
>    Affects Versions: 0.11.1
>            Reporter: Antoine Pitrou
>            Priority: Major
>             Fix For: 1.0.0
>
>
> This issue was found by Coverity. The {{RleDecoder::NextCounts}} method has 
> the following code to fetch the repeated literal in repeated runs:
> {code:c++}
>     bool result =
>         
> bit_reader_.GetAligned<T>(static_cast<int>(BitUtil::CeilDiv(bit_width_, 8)),
>                                   reinterpret_cast<T*>(&current_value_));
> {code}
> Coverity says this:
> bq. 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.
> bq. 
> 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).



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