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https://issues.apache.org/jira/browse/HIVE-6264?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13879079#comment-13879079
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Jason Dere commented on HIVE-6264:
----------------------------------
https://reviews.apache.org/r/17200/
> Unbalanced number of HiveParser msgs.push/msgs.pop calls when doing lookahead
> -----------------------------------------------------------------------------
>
> Key: HIVE-6264
> URL: https://issues.apache.org/jira/browse/HIVE-6264
> Project: Hive
> Issue Type: Bug
> Reporter: Jason Dere
> Assignee: Jason Dere
> Attachments: HIVE-6264.1.patch
>
>
> HiveParser pushes/pops messages describing the current parse rule like so:
> {noformat}
> joinSource
> @init { gParent.msgs.push("join source"); }
> @after { gParent.msgs.pop(); }
> ...
> {noformat}
> The ANTLR generated code for the init/after actions looks like this:
> {noformat}
> gParent.msgs.push("join source");
> ...
> if ( state.backtracking==0 ) { gParent.msgs.pop(); }
> {noformat}
> If we have a parse rule that does some lookahead, the message is always
> pushed onto the message stack since the init action has no check of
> state.backtracking. But that message is never popped because the after
> action does check state.backtracking. As a result there can be a bunch of
> parser context messages added to the stack which are never taken off.
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