[Hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1885) LA(0) is undefined

[Brian C. (JIRA) <no...@at...>]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1885?page=comments#action_23649 ] 

Brian Cox commented on HHH-1885:
--------------------------------

Further investigation shows that one way this can happen is after the TokenQueue.expand() method has been called.
The new queue elements will be NULL; therefore, LT(0) will return NULL and LA(0) will throw a NullPtrExcp.

> LA(0) is undefined
> ------------------
>
>          Key: HHH-1885
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1885
>      Project: Hibernate3
>         Type: Bug

>   Components: query-hql
>     Versions: 3.1.2
>  Environment: Hibernate 3.1.2  Postgres 8.1.2
>     Reporter: Brian Cox

>
>
> method weakKeywords() in org.hibernate.hql.ast.HqlParser.java has:
> if (LA(0) == FROM && t != IDENT && LA(2) == DOT) {
> ...
> }
> According to a posting on the antlr mailing list [see "LT(0) Specification" posted 1 July 2006],
> LA(i) and LT(i) are defined only for i > 0. Examining the code supports this assertion.  Also these
> methods are documented as "lookahead" not "lookbehind".  LT(0) can return NULL and then LA(0)
> will throw a NullPointerException as shown:
> java.lang.NullPointerException
> 	at antlr.TokenBuffer.LA(TokenBuffer.java:81)
> 	at antlr.LLkParser.LA(LLkParser.java:52)
> 	at org.hibernate.hql.ast.HqlParser.weakKeywords(HqlParser.java:296)
> 	at org.hibernate.hql.antlr.HqlBaseParser.negatedExpression(HqlBaseParser.java:2366)
> 	at org.hibernate.hql.antlr.HqlBaseParser.logicalAndExpression(HqlBaseParser.java:2331)
> 	at org.hibernate.hql.antlr.HqlBaseParser.logicalOrExpression(HqlBaseParser.java:2296)
> 	at org.hibernate.hql.antlr.HqlBaseParser.expression(HqlBaseParser.java:2082)
> 	at org.hibernate.hql.antlr.HqlBaseParser.compoundExpr(HqlBaseParser.java:2991)
> 	at org.hibernate.hql.antlr.HqlBaseParser.inList(HqlBaseParser.java:2858)
> 	at org.hibernate.hql.antlr.HqlBaseParser.relationalExpression(HqlBaseParser.java:2720)
> 	at org.hibernate.hql.antlr.HqlBaseParser.equalityExpression(HqlBaseParser.java:2449)
> 	at org.hibernate.hql.antlr.HqlBaseParser.negatedExpression(HqlBaseParser.java:2413)
> 	at org.hibernate.hql.antlr.HqlBaseParser.logicalAndExpression(HqlBaseParser.java:2331)
> 	at org.hibernate.hql.antlr.HqlBaseParser.logicalOrExpression(HqlBaseParser.java:2296)
> 	at org.hibernate.hql.antlr.HqlBaseParser.expression(HqlBaseParser.java:2082)
> 	at org.hibernate.hql.antlr.HqlBaseParser.logicalExpression(HqlBaseParser.java:1858)
> 	at org.hibernate.hql.antlr.HqlBaseParser.whereClause(HqlBaseParser.java:454)
> 	at org.hibernate.hql.antlr.HqlBaseParser.updateStatement(HqlBaseParser.java:224)
> 	at org.hibernate.hql.antlr.HqlBaseParser.statement(HqlBaseParser.java:142)
> 	at org.hibernate.hql.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:238)
> 	at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:155)
> 	at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:109)
> 	at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:75)
> 	at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:54)
> 	at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:71)
> 	at org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:134)
> 	at org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:113)
> 	at org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1602)
> 	at com.timestock.tess.util.DbUtils.saveUpdatedUsers(DbUtils.java:38)
> 	at com.timestock.tess.services.collectors.StatsCollector$StatisticsCollector.run(StatsCollector.java:602)
> 	at java.util.TimerThread.mainLoop(Timer.java:512)
> 	at java.util.TimerThread.run(Timer.java:462)

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