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From "Chris Koenig (JIRA)" <>
Subject [jira] [Created] (LUCENE-7916) CompositeBreakIterator is brittle under ICU4J upgrade.
Date Tue, 01 Aug 2017 17:39:00 GMT
Chris Koenig created LUCENE-7916:

             Summary: CompositeBreakIterator is brittle under ICU4J upgrade.
                 Key: LUCENE-7916
             Project: Lucene - Core
          Issue Type: Bug
          Components: modules/analysis
    Affects Versions: 6.6
            Reporter: Chris Koenig

We use lucene-analyzers-icu version 6.6.0 in our project. Lucene 6.6.0 is built against ICU4J
version 56.1, but our use case requires us to use the latest version of ICU4J, 59.1.

The problem that we have encountered is that CompositeBreakIterator.getBreakIterator(int scriptCode)
throws an ArrayIndexOutOfBoundsException for script codes higher than 167. In ICU4J 56.1 the
highest possible script code is 166, but in ICU4j 59.1 it is 174.

Internally, CompositeBreakIterator is creating an array of size UScript.CODE_LIMIT, but the
value of CODE_LIMIT from ICU4J 56.1 is being baked into the bytecode by the compiler. So even
after overriding the version of the ICU4J dependency to 59.1 in our project, this array will
still be size 167, which is too small.

final class CompositeBreakIterator {
  private final ICUTokenizerConfig config;
  private final BreakIteratorWrapper wordBreakers[] = new BreakIteratorWrapper[UScript.CODE_LIMIT];

Output of javap run on CompositeBreakIterator.class from lucene-analyzers-icu-6.6.0.jar
Compiled from ""
final class {;
    descriptor: (Lorg/apache/lucene/analysis/icu/segmentation/ICUTokenizerConfig;)V
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: aload_0
       5: sipush        167
       8: anewarray     #3                  // class org/apache/lucene/analysis/icu/segmentation/BreakIteratorWrapper

In our case, the ArrayIndexOutOfBoundsException was triggered when we encountered a stray
character of the Bhaiksuki script (script code 168) in a chunk of text that we processed.

CompositeBreakIterator can be made more resilient by changing the type of wordBreakers from
an array to a Map and no longer relying on the value of UScript.CODE_LIMIT.

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