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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11221) JAVA specification for hashcode does not enforce it to be non-negative, but IdentityHashStore assumes System.identityHashCode() is non-negative
Date Fri, 31 Oct 2014 13:20:38 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14191788#comment-14191788
] 

Hudson commented on HADOOP-11221:
---------------------------------

FAILURE: Integrated in Hadoop-Hdfs-trunk #1918 (See [https://builds.apache.org/job/Hadoop-Hdfs-trunk/1918/])
HADOOP-11221. IdentityHashStore assumes System.identityHashCode() is non-negative. Contributed
by Jinghui Wang (szetszwo: rev a3dacc07e2c08bb4ecfce7b5e6d5602273989e9c)
* hadoop-common-project/hadoop-common/CHANGES.txt
* hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/IdentityHashStore.java


> JAVA specification for hashcode does not enforce it to be non-negative, but IdentityHashStore
assumes System.identityHashCode() is non-negative
> -----------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-11221
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11221
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: util
>    Affects Versions: 2.4.1
>            Reporter: Jinghui Wang
>            Assignee: Jinghui Wang
>             Fix For: 2.6.0
>
>         Attachments: HADOOP-11221.patch, HADOOP-11221.v1.patch, HADOOP-11221.v2.patch,
HADOOP-11221.v3.patch
>
>
> The following code snippet shows that IdentityHashStore assumes the hashCode is always
non-negative.
> {code:borderStyle=solid}
>    private void putInternal(Object k, Object v) {
>      int hash = System.identityHashCode(k);
>      final int numEntries = buffer.length / 2;
>      int index = hash % numEntries;
> 	 ...
>    }
>    
>   private int getElementIndex(K k) {
>      ...
>      final int numEntries = buffer.length / 2;
>      int hash = System.identityHashCode(k);
>      int index = hash % numEntries;
>      int firstIndex = index;
>      ...
>   }
> {code}



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