Bug in Bytecode Verifier

[David Foster]

Here's a little gem that causes BCEL's verifier to crash:

.class public Test47
.super java/lang/Object
.method public foo(B)V
        .limit stack 10
        .limit locals 10
        
        iload_1
        ifne ELSE_0
                new java/io/BufferedInputStream
                goto ENDIF_0
        ELSE_0:
                new java/io/FilterInputStream
        ENDIF_0:
        pop
        
        return
.end method
The error generated is as follows:

Exception in thread "main"  
org.apache.bcel.verifier.exc.AssertionViolatedException: INTERNAL  
ERROR: Some RuntimeException occured while verify()ing class 'Test47',  
method 'public void foo(byte arg1)'. Original RuntimeException's stack  
trace:
---
java.lang.ClassCastException
        at  
org.apache.bcel.generic.ReferenceType.getFirstCommonSuperclass(Reference 
Type.java:256)
        at  
org.apache.bcel.verifier.structurals.OperandStack.merge(OperandStack.jav 
a:254)
        at  
org.apache.bcel.verifier.structurals.ControlFlowGraph$InstructionContext 
Impl.mergeInFrames(ControlFlowGraph.java:246)
        at  
org.apache.bcel.verifier.structurals.ControlFlowGraph$InstructionContext 
Impl.execute(ControlFlowGraph.java:189)
        at  
org.apache.bcel.verifier.structurals.Pass3bVerifier.circulationPump(Pass 
3bVerifier.java:228)
        at  
org.apache.bcel.verifier.structurals.Pass3bVerifier.do_verify(Pass3bVeri 
fier.java:342)
        at  
org.apache.bcel.verifier.PassVerifier.verify(PassVerifier.java:108)
        at org.apache.bcel.verifier.Verifier.doPass3b(Verifier.java:133)
        at ClassVerifier.verify(ClassVerifier.java:33)
        at ClassInfo.verify(ClassInfo.java:51)
        at Main.main(Main.java:7)
---

        at  
org.apache.bcel.verifier.structurals.Pass3bVerifier.do_verify(Pass3bVeri 
fier.java:356)
        at  
org.apache.bcel.verifier.PassVerifier.verify(PassVerifier.java:108)
        at org.apache.bcel.verifier.Verifier.doPass3b(Verifier.java:133)
        at ClassVerifier.verify(ClassVerifier.java:33)
        at ClassInfo.verify(ClassInfo.java:51)
        at Main.main(Main.java:7)

It appears that ReferenceType.getFirstCommonSuperclass() is not  
designed to handle the  
org.apache.bcel.verifier.structurals.UninitializedObjectType  
ReferenceType that is used by BCEL's verifier.

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