Missing stack traces for repeated exceptions (reminder)

A long while ago a optimisation was added to the JVM so that if the same exception is thrown again and again and again a single instance of the Exception is created without the stack trace filled in in order to increase performance. This is an excellent idea unless you are trying to diagnose a problem and you have missed the original error.

If you forgot about this optimisation you send the afternoon looking at the following log output and weeping slightly. (In my defence I have a little one in the house hence the fuzzy brain and lack of blogging action this year)

java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
java.lang.ArrayIndexOutOfBoundsException
...
java.lang.Exception: Uncaught exceptions during test
 at oracle.jdevstudio-testware-tests.level0.testADFcMATS(/.../work/mw9111/jdeveloper/jdev/extensions/oracle.jdevstudio-testware-tests/abbot/common-adf/CreateNewCustomAppAndProjectWithName.xml:25)
 at oracle.jdevstudio-testware-tests.level0.testADFcMATS(/.../work/mw9111/jdeveloper/jdev/extensions/oracle.jdevstudio-testware-tests/abbot/level0/testADFcMATS.xml:94)
 at oracle.abbot.JDevScriptFixture.runTest(JDevScriptFixture.java:555)
 at junit.framework.TestCase.runBare(TestCase.java:134)
 at junit.framework.TestResult$1.protect(TestResult.java:110)
 at junit.framework.TestResult.runProtected(TestResult.java:128)
 at junit.framework.TestResult.run(TestResult.java:113)
 at junit.framework.TestCase.run(TestCase.java:124)
 at junit.framework.TestSuite.runTest(TestSuite.java:243)
 at junit.framework.TestSuite.run(TestSuite.java:238)
 at junit.textui.TestRunner.doRun(TestRunner.java:116)
 at junit.textui.TestRunner.doRun(TestRunner.java:109)
 at oracle.abbot.AbbotRunner.run(AbbotRunner.java:614)
 at oracle.abbot.AbbotAddin$IdeAbbotRunner.run(AbbotAddin.java:634)
 at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ArrayIndexOutOfBoundsException

[Crickets]

It turns out that you can turn off this optimisation with a simple flag:

java -XX:-OmitStackTraceInFastThrow ....

In my particular case the actual exception causing this trouble was a NPE from the GlyphView code in JDK8. (One that is being caused by a glitch in hotspot it seems) But that in turn was causing the AIOOBE in some logging code clouding the issue even more.

This in particular is a good flag to add by default when running your automated tests, particularly in combination with the stack trace length override I have talked about before.