[jboss-jira] [JBoss JIRA] Created: (JASSIST-72) Instrumenting write access using CodeConverter.replaceArrayAccess(...) causes VerifyError (Unable to pop operand off an empty stack) - buggy aastore

[Martin Burger (JIRA)]

Instrumenting write access using CodeConverter.replaceArrayAccess(...) causes VerifyError (Unable to pop operand off an empty stack) - buggy aastore
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                 Key: JASSIST-72
                 URL: https://jira.jboss.org/jira/browse/JASSIST-72
             Project: Javassist
          Issue Type: Bug
         Environment: javassist 3.9.0.GA
            Reporter: Martin Burger
            Assignee: Shigeru Chiba


I use Javassist to instrument class files in order to catch some runtime information. Basically, I insert probes to get information about method calls, field accesses, and so on. This includes access to arrays. Unfortunately, when I instrument array accesses using CodeConverter.replaceArrayAccess(...) the Java verifier throws an exception while loading the changed method: Unable to pop operand off an empty stack.

Instrumenting array accesses is one instrumentation of many. If I disable instrumentation of array accesses, the instrumented program will run and I will get runtime information about method calls etc. As soon as I enable the instrumentation of arrays, the byte code created by javassist causes the java.lang.VerifyError mentioned above.

The buggy byte code instruction seems to be:

   7016:	anewarray	#51; //class java/lang/Object
   7019:	dup
   7020:	iconst_0
   7021:	iload_1
   7022:	bipush	56
   7024:	if_icmpne	7036
   7027:	ldc_w	#5369; //String 8
   7030:	nop
   7031:	nop
   7032:	nop
   7033:	goto	7042
   7036:	ldc_w	#5371; //String 9
   7039:	nop
   7040:	nop
   7041:	nop
   7042:	invokestatic	#5373;
   7045:	nop
   7046:	aastore <-- causes VerifyError

At least when executing aastore the stack is empty already.

The original source code:

if (base == 8 && c >= '8') {
    Object[] errArgs = { c == '8' ? "8" : "9" };
    reportCurrentLineWarning(
        "msg.bad.octal.literal", errArgs);
    base = 10;
}


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