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Posted to issues-all@impala.apache.org by "Daniel Becker (Jira)" <ji...@apache.org> on 2019/08/21 08:32:00 UTC
[jira] [Resolved] (IMPALA-8846) Undefined behaviour in
RleEncoder::Put
[ https://issues.apache.org/jira/browse/IMPALA-8846?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Daniel Becker resolved IMPALA-8846.
-----------------------------------
Resolution: Fixed
> Undefined behaviour in RleEncoder::Put
> --------------------------------------
>
> Key: IMPALA-8846
> URL: https://issues.apache.org/jira/browse/IMPALA-8846
> Project: IMPALA
> Issue Type: Bug
> Reporter: Daniel Becker
> Assignee: Daniel Becker
> Priority: Major
> Attachments: original.txt, with_check.txt
>
>
> On line [https://github.com/apache/impala/blob/4000da35be69e469500f5f11e0e5fdec119cf5c7/be/src/util/rle-encoding.h#L346,] we test repeat_count_ <= std::numeric_limits<int32_t>::max(), which is always true (repeat_count_ is an int), then we increment repeat_count which could be std::numeric_limits<int32_t>::max() and overflow, which is undefined behaviour for signed integers.
>
> We should either change <= to < or if we think that this never happens, remove the misleading check.
> If we correct the check, it may lead to some (probably small) performance regression because the compiler could have optimised this out.
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