Message8622

PySystemState initStaticFields and initBuildins initialize PyTypes before Py.False and Py.True are initialized. Intermittently this leads to ExceptionInInitializerError thrown due to a NullPointer exception in PyObject._cmpeq_unsafe.

Stack trace:

Exception in thread "main" java.lang.ExceptionInInitializerError	at org.python.core.PySystemState.initStaticFields(PySystemState.java:912)
	at org.python.core.PySystemState.doInitialize(PySystemState.java:882)
	at org.python.core.PySystemState.initialize(PySystemState.java:800)
	at org.python.core.PySystemState.initialize(PySystemState.java:750)
	at org.python.core.PySystemState.initialize(PySystemState.java:743)
	at org.python.util.jython.run(jython.java:150)
	at org.python.util.jython.main(jython.java:129)
Caused by: java.lang.NullPointerException
	at org.python.core.PyObject._cmpeq_unsafe(PyObject.java:1362)
	at org.python.core.PyObject._eq(PyObject.java:1456)
	at org.python.core.PyObject.equals(PyObject.java:244)
	at java.util.HashMap.put(HashMap.java:475)
	at java.util.HashSet.add(HashSet.java:217)
	at org.python.core.PyType.fromClass(PyType.java:1317)
	at org.python.core.PyType.fromClass(PyType.java:1275)
	at org.python.core.PyEllipsis.<clinit>(PyEllipsis.java:14)
	at java.lang.J9VMInternals.initializeImpl(Native Method)
	at java.lang.J9VMInternals.initialize(J9VMInternals.java:236)
	... 7 more

Root cause of the problem is that PyType.fromClass stores all types in a HashSet exposedTypes. If during initialization two PyTypes end up having the same hashCode, the HashSet uses the method equals. Some methods called by PyObject.equals return Py.True/Py.False (see PyObject._is) which aren't initialized as first PyTypes...

We have seen this error only on AIX systems and with an application that generated +10000 Jython runs per day.

One fix would be to ensure PyTrue and PyFalse get initialized right at the start of the PyType initialization. See the attached.

public static synchronized PyType fromClass(Class<?> c) {
    	
    	// HP Debug
    	if (Py.False == null) Py.False = new PyBoolean(false);
    	if (Py.True == null) Py.True = new PyBoolean(true);
    	
        return fromClass(c, true);
    }

This isn't elegant. There should be a better way to fix the issue.