When running Drools unit tests on Solaris with Sun JDK 6, the following test throws a SOE:

org.drools.jsr94.rules.StatefulRuleSessionTest.testContainsObject

java.lang.StackOverflowError
	at java.util.regex.Pattern$Loop.match(Pattern.java:4275)
	at java.util.regex.Pattern$GroupTail.match(Pattern.java:4227)
	at java.util.regex.Pattern$BranchConn.match(Pattern.java:4078)
	at java.util.regex.Pattern$CharProperty.match(Pattern.java:3345)
	at java.util.regex.Pattern$Branch.match(Pattern.java:4114)
	at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168)
	at java.util.regex.Pattern$Loop.match(Pattern.java:4295)
...

Turns out this is because of a bug in Sun JDK that will never be fixed:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5050507

There is also a workaround that should be implemented in order to get this fixed.