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From "Jason Dere (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-6264) Unbalanced number of HiveParser msgs.push/msgs.pop calls when doing lookahead
Date Wed, 22 Jan 2014 19:13:25 GMT
Jason Dere created HIVE-6264:
--------------------------------

             Summary: 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


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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