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I'm using JPhantom as part of an a preprocessing tool for static analysis of Android. I've found JPhantom to be extremely useful for this task, but it occasionally crashes with the following error when I use it to fill in missing dependencies in the Android library:

Exception in thread "main" java.lang.NullPointerException
at jphantom.tree.AbstractClassHierarchy.checkedObject(AbstractClassHierarchy.java:14)
at jphantom.tree.IncrementalClassHierarchy.contains(IncrementalClassHierarchy.java:109)
at jphantom.ClassMembers$Record.lookupField(ClassMembers.java:82)
at jphantom.ClassMembers.lookupField(ClassMembers.java:30)
at jphantom.adapters.ClassPhantomExtractor$MethodPhantomExtractor.visitFieldInsn(ClassPhantomExtractor.java:403)
at org.objectweb.asm.ClassReader.readCode(ClassReader.java:1318)
at org.objectweb.asm.ClassReader.readMethod(ClassReader.java:938)
at org.objectweb.asm.ClassReader.accept(ClassReader.java:669)
at org.objectweb.asm.ClassReader.accept(ClassReader.java:506)
at jphantom.Driver.(Driver.java:82)
at jphantom.Driver.(Driver.java:44)
at jphantom.Driver.main(Driver.java:314)

I've sent you a JAR that exhibits this problem via email since it is too big to attach here.

I currently work around this problem by in ClassPhantomExtractor by replacing

FieldSignature sign = members.lookupField(phantom, name);

with

FieldSignature sign = null;
try {
  sign = members.lookupField(phantom, name);            
} catch (NullPointerException e) {              
  System.out.println("WARNING! Lookup of " + name + " in " + phantom + " failed.");
  break;
}

Clearly, this is not ideal, but it allows JPhantom to continue the complementation without crashing. I'm guessing there is a much better fix than this, but I don't understand the internals of JPhantom enough to know what it is.

Hi George,
I'm getting an NPE in ClassMembers$Record:

Exception in thread "main" java.lang.NullPointerException
at jphantom.ClassMembers$Record.lookupIMethod(ClassMembers.java:199)
at jphantom.ClassMembers$Record.lookupMethod(ClassMembers.java:148)
at jphantom.ClassMembers.lookupMethod(ClassMembers.java:49)
at jphantom.adapters.ClassPhantomExtractor$MethodPhantomExtractor.visitMethodInsn(ClassPhantomExtractor.java:260)
at org.objectweb.asm.ClassReader.readCode(ClassReader.java:1320)
at org.objectweb.asm.ClassReader.readMethod(ClassReader.java:938)
at org.objectweb.asm.ClassReader.accept(ClassReader.java:669)
at org.objectweb.asm.ClassReader.accept(ClassReader.java:506)
at jphantom.Driver.(Driver.java:82)
at jphantom.Driver.(Driver.java:44)
at jphantom.Driver.main(Driver.java:314)

I took a quick look at it and it appears that the problem is that the rec local is null, but I could not easily tell whether the right fix would be adding a guard or fixing up a broken invariant elsewhere.

As before, the JAR that causes the issue is quite large (contains the entire Android library). so I have posted it here instead.

Sam

On class jphantom.hier.ClassHierarchies.java, method ClassHierarchy fromJar(JarFile file) around this statement:

Type clazz = Type.getObjectType(reader.getClassName());                    
Type superclass = Type.getObjectType(reader.getSuperName());

When reader is of the type Object, the superName will be null, thus it throws NPE. However when I tried to patch it myself by continuing loop when it finds superName == null, it still throws RuntimeException.

I tested with this apk https://github.com/chighwater/mirror/blob/master/me.organize.android.apk
Please let me know if you need any test files because JPhantom was run via Droidel.
Thank you.