/*
    * Copyright  2000-2004 The Apache Software Foundation
    *
    *  Licensed under the Apache License, Version 2.0 (the "License"); 
    *  you may not use this file except in compliance with the License.
    *  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
    *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License. 
   *
   */ 
  package org.apache.bcel.verifier.structurals;
  
  
  import org.apache.bcel.Constants;
  import org.apache.bcel.Repository;
  import org.apache.bcel.classfile.Constant;
  import org.apache.bcel.classfile.ConstantClass;
  import org.apache.bcel.classfile.ConstantDouble;
  import org.apache.bcel.classfile.ConstantFieldref;
  import org.apache.bcel.classfile.ConstantFloat;
  import org.apache.bcel.classfile.ConstantInteger;
  import org.apache.bcel.classfile.ConstantLong;
  import org.apache.bcel.classfile.ConstantString;
  import org.apache.bcel.classfile.Field;
  import org.apache.bcel.classfile.JavaClass;
  import org.apache.bcel.generic.*;
  import org.apache.bcel.verifier.VerificationResult;
  import org.apache.bcel.verifier.Verifier;
  import org.apache.bcel.verifier.VerifierFactory;
  import org.apache.bcel.verifier.exc.AssertionViolatedException;
  import org.apache.bcel.verifier.exc.StructuralCodeConstraintException;
  
  
  /***
   * A Visitor class testing for valid preconditions of JVM instructions.
   * The instance of this class will throw a StructuralCodeConstraintException
   * instance if an instruction is visitXXX()ed which has preconditions that are
   * not satisfied.
   * TODO: Currently, the JVM's behaviour concerning monitors (MONITORENTER,
   * MONITOREXIT) is not modeled in JustIce.
   *
   * @version $Id: InstConstraintVisitor.java 386056 2006-03-15 11:31:56Z tcurdt $
   * @author Enver Haase
   * @see org.apache.bcel.verifier.exc.StructuralCodeConstraintException
   * @see org.apache.bcel.verifier.exc.LinkingConstraintException
   */
  public class InstConstraintVisitor extends EmptyVisitor implements org.apache.bcel.generic.Visitor{
  
  	private static ObjectType GENERIC_ARRAY = new ObjectType("org.apache.bcel.verifier.structurals.GenericArray");
  
  	/***
  	 * The constructor. Constructs a new instance of this class.
  	 */
  	public InstConstraintVisitor(){}
  
  	/***
  	 * The Execution Frame we're working on.
  	 *
  	 * @see #setFrame(Frame f)
  	 * @see #locals()
  	 * @see #stack()
  	 */
  	private Frame frame = null;
  
  	/***
  	 * The ConstantPoolGen we're working on.
  	 * 
  	 * @see #setConstantPoolGen(ConstantPoolGen cpg)
  	 */
  	private ConstantPoolGen cpg = null;
  
  	/***
  	 * The MethodGen we're working on.
  	 * 
  	 * @see #setMethodGen(MethodGen mg)
  	 */
  	private MethodGen mg = null;
  
  	/***
  	 * The OperandStack we're working on.
  	 *
  	 * @see #setFrame(Frame f)
  	 */
  	private OperandStack stack(){
  		return frame.getStack();
  	}
  
  	/***
  	 * The LocalVariables we're working on.
  	 *
  	 * @see #setFrame(Frame f)
  	 */
  	private LocalVariables locals(){
 		return frame.getLocals();
 	}
 
 	/***
    * This method is called by the visitXXX() to notify the acceptor of this InstConstraintVisitor
    * that a constraint violation has occured. This is done by throwing an instance of a
    * StructuralCodeConstraintException.
    * @throws org.apache.bcel.verifier.exc.StructuralCodeConstraintException always.
    */
 	private void constraintViolated(Instruction violator, String description){
 		String fq_classname = violator.getClass().getName();
 		throw new StructuralCodeConstraintException("Instruction "+ fq_classname.substring(fq_classname.lastIndexOf('.')+1) +" constraint violated: " + description);
 	}
 
 	/***
 	 * This returns the single instance of the InstConstraintVisitor class.
 	 * To operate correctly, other values must have been set before actually
 	 * using the instance.
 	 * Use this method for performance reasons.
 	 *
 	 * @see #setConstantPoolGen(ConstantPoolGen cpg)
 	 * @see #setMethodGen(MethodGen mg)
 	 */
 	public void setFrame(Frame f){
 		this.frame = f;
 		//if (singleInstance.mg == null || singleInstance.cpg == null) throw new AssertionViolatedException("Forgot to set important values first.");
 	}
 
 	/***
 	 * Sets the ConstantPoolGen instance needed for constraint
 	 * checking prior to execution.
 	 */	
 	public void setConstantPoolGen(ConstantPoolGen cpg){
 		this.cpg = cpg;
 	}
 
 	/***
 	 * Sets the MethodGen instance needed for constraint
 	 * checking prior to execution.
 	 */
 	public void setMethodGen(MethodGen mg){
 		this.mg = mg;
 	}
 
 	/***
 	 * Assures index is of type INT.
 	 * @throws org.apache.bcel.verifier.exc.StructuralCodeConstraintException if the above constraint is not satisfied.
 	 */
 	private void indexOfInt(Instruction o, Type index){
 		if (! index.equals(Type.INT)) {
             constraintViolated(o, "The 'index' is not of type int but of type "+index+".");
         }
 	}
 
 	/***
 	 * Assures the ReferenceType r is initialized (or Type.NULL).
 	 * Formally, this means (!(r instanceof UninitializedObjectType)), because
 	 * there are no uninitialized array types.
 	 * @throws org.apache.bcel.verifier.exc.StructuralCodeConstraintException if the above constraint is not satisfied.
 	 */
 	private void referenceTypeIsInitialized(Instruction o, ReferenceType r){
 		if (r instanceof UninitializedObjectType){
 			constraintViolated(o, "Working on an uninitialized object '"+r+"'.");
 		}
 	}
 
 	/*** Assures value is of type INT. */
 	private void valueOfInt(Instruction o, Type value){
 		if (! value.equals(Type.INT)) {
             constraintViolated(o, "The 'value' is not of type int but of type "+value+".");
         }
 	}
 
 	/***
 	 * Assures arrayref is of ArrayType or NULL;
 	 * returns true if and only if arrayref is non-NULL.
 	 * @throws org.apache.bcel.verifier.exc.StructuralCodeConstraintException if the above constraint is violated.
  	 */
 	private boolean arrayrefOfArrayType(Instruction o, Type arrayref){
 		if (! ((arrayref instanceof ArrayType) || arrayref.equals(Type.NULL)) ) {
             constraintViolated(o, "The 'arrayref' does not refer to an array but is of type "+arrayref+".");
         }
 		return (arrayref instanceof ArrayType);
 	}
 
 	/****************************************************************/
 	/* MISC                                                        */
 	/****************************************************************/
 	/***
 	 * Ensures the general preconditions of an instruction that accesses the stack.
 	 * This method is here because BCEL has no such superinterface for the stack
 	 * accessing instructions; and there are funny unexpected exceptions in the
 	 * semantices of the superinterfaces and superclasses provided.
 	 * E.g. SWAP is a StackConsumer, but DUP_X1 is not a StackProducer.
 	 * Therefore, this method is called by all StackProducer, StackConsumer,
 	 * and StackInstruction instances via their visitXXX() method.
 	 * Unfortunately, as the superclasses and superinterfaces overlap, some instructions
 	 * cause this method to be called two or three times. [TODO: Fix this.]
 	 *
 	 * @see #visitStackConsumer(StackConsumer o)
 	 * @see #visitStackProducer(StackProducer o)
 	 * @see #visitStackInstruction(StackInstruction o)
 	 */
 	private void _visitStackAccessor(Instruction o){
 		int consume = o.consumeStack(cpg); // Stack values are always consumed first; then produced.
 		if (consume > stack().slotsUsed()){
 			constraintViolated((Instruction) o, "Cannot consume "+consume+" stack slots: only "+stack().slotsUsed()+" slot(s) left on stack!\nStack:\n"+stack());
 		}
 
 		int produce = o.produceStack(cpg) - ((Instruction) o).consumeStack(cpg); // Stack values are always consumed first; then produced.
 		if ( produce + stack().slotsUsed() > stack().maxStack() ){
 			constraintViolated((Instruction) o, "Cannot produce "+produce+" stack slots: only "+(stack().maxStack()-stack().slotsUsed())+" free stack slot(s) left.\nStack:\n"+stack());
 		}
 	}
 
 	/****************************************************************/
 	/* "generic"visitXXXX methods where XXXX is an interface       */
 	/* therefore, we don't know the order of visiting; but we know */
 	/* these methods are called before the visitYYYY methods below */
 	/****************************************************************/
 
 	/***
 	 * Assures the generic preconditions of a LoadClass instance.
 	 * The referenced class is loaded and pass2-verified.
 	 */
 	public void visitLoadClass(LoadClass o){
 		ObjectType t = o.getLoadClassType(cpg);
 		if (t != null){// null means "no class is loaded"
 			Verifier v = VerifierFactory.getVerifier(t.getClassName());
 			VerificationResult vr = v.doPass2();
 			if (vr.getStatus() != VerificationResult.VERIFIED_OK){
 				constraintViolated((Instruction) o, "Class '"+o.getLoadClassType(cpg).getClassName()+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
 			}
 		}
 	}
 
 	/***
 	 * Ensures the general preconditions of a StackConsumer instance.
 	 */
 	public void visitStackConsumer(StackConsumer o){
 		_visitStackAccessor((Instruction) o);
 	}
 	
 	/***
 	 * Ensures the general preconditions of a StackProducer instance.
 	 */
 	public void visitStackProducer(StackProducer o){
 		_visitStackAccessor((Instruction) o);
 	}
 
 
 	/****************************************************************/
 	/* "generic" visitYYYY methods where YYYY is a superclass.     */
 	/* therefore, we know the order of visiting; we know           */
 	/* these methods are called after the visitXXXX methods above. */
 	/****************************************************************/
 	/***
 	 * Ensures the general preconditions of a CPInstruction instance.
 	 */
 	public void visitCPInstruction(CPInstruction o){
 		int idx = o.getIndex();
 		if ((idx < 0) || (idx >= cpg.getSize())){
 			throw new AssertionViolatedException("Huh?! Constant pool index of instruction '"+o+"' illegal? Pass 3a should have checked this!");
 		}
 	}
 
 	/***
 	 * Ensures the general preconditions of a FieldInstruction instance.
 	 */
 	 public void visitFieldInstruction(FieldInstruction o){
 	 	// visitLoadClass(o) has been called before: Every FieldOrMethod
 	 	// implements LoadClass.
 	 	// visitCPInstruction(o) has been called before.
 		// A FieldInstruction may be: GETFIELD, GETSTATIC, PUTFIELD, PUTSTATIC 
 			Constant c = cpg.getConstant(o.getIndex());
 			if (!(c instanceof ConstantFieldref)){
 				constraintViolated(o, "Index '"+o.getIndex()+"' should refer to a CONSTANT_Fieldref_info structure, but refers to '"+c+"'.");
 			}
 			// the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
 			Type t = o.getType(cpg);
 			if (t instanceof ObjectType){
 				String name = ((ObjectType)t).getClassName();
 				Verifier v = VerifierFactory.getVerifier( name );
 				VerificationResult vr = v.doPass2();
 				if (vr.getStatus() != VerificationResult.VERIFIED_OK){
 					constraintViolated((Instruction) o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
 				}
 			}
 	 }
 	 
 	/***
 	 * Ensures the general preconditions of an InvokeInstruction instance.
 	 */
 	 public void visitInvokeInstruction(InvokeInstruction o){
 	 	// visitLoadClass(o) has been called before: Every FieldOrMethod
 	 	// implements LoadClass.
 	 	// visitCPInstruction(o) has been called before.
         //TODO
 	 }
 	 
 	/***
 	 * Ensures the general preconditions of a StackInstruction instance.
 	 */
 	public void visitStackInstruction(StackInstruction o){
 		_visitStackAccessor(o);
 	}
 
 	/***
 	 * Assures the generic preconditions of a LocalVariableInstruction instance.
 	 * That is, the index of the local variable must be valid.
 	 */
 	public void visitLocalVariableInstruction(LocalVariableInstruction o){
 		if (locals().maxLocals() <= (o.getType(cpg).getSize()==1? o.getIndex() : o.getIndex()+1) ){
 			constraintViolated(o, "The 'index' is not a valid index into the local variable array.");
 		}
 	}
 	
 	/***
 	 * Assures the generic preconditions of a LoadInstruction instance.
 	 */
 	public void visitLoadInstruction(LoadInstruction o){
 		//visitLocalVariableInstruction(o) is called before, because it is more generic.
 
 		// LOAD instructions must not read Type.UNKNOWN
 		if (locals().get(o.getIndex()) == Type.UNKNOWN){
 			constraintViolated(o, "Read-Access on local variable "+o.getIndex()+" with unknown content.");
 		}
 
 		// LOAD instructions, two-slot-values at index N must have Type.UNKNOWN
 		// as a symbol for the higher halve at index N+1
 		// [suppose some instruction put an int at N+1--- our double at N is defective]
 		if (o.getType(cpg).getSize() == 2){
 			if (locals().get(o.getIndex()+1) != Type.UNKNOWN){
 				constraintViolated(o, "Reading a two-locals value from local variables "+o.getIndex()+" and "+(o.getIndex()+1)+" where the latter one is destroyed.");
 			}
 		}
 
 		// LOAD instructions must read the correct type.
 		if (!(o instanceof ALOAD)){
 			if (locals().get(o.getIndex()) != o.getType(cpg) ){
 				constraintViolated(o, "Local Variable type and LOADing Instruction type mismatch: Local Variable: '"+locals().get(o.getIndex())+"'; Instruction type: '"+o.getType(cpg)+"'.");
 			}
 		}
 		else{ // we deal with an ALOAD
 			if (!(locals().get(o.getIndex()) instanceof ReferenceType)){
 				constraintViolated(o, "Local Variable type and LOADing Instruction type mismatch: Local Variable: '"+locals().get(o.getIndex())+"'; Instruction expects a ReferenceType.");
 			}
 			// ALOAD __IS ALLOWED__ to put uninitialized objects onto the stack!
 			//referenceTypeIsInitialized(o, (ReferenceType) (locals().get(o.getIndex())));
 		}
 
 		// LOAD instructions must have enough free stack slots.
 		if ((stack().maxStack() - stack().slotsUsed()) < o.getType(cpg).getSize()){
 			constraintViolated(o, "Not enough free stack slots to load a '"+o.getType(cpg)+"' onto the OperandStack.");
 		}
 	}
 
 	/***
 	 * Assures the generic preconditions of a StoreInstruction instance.
 	 */
 	public void visitStoreInstruction(StoreInstruction o){
 		//visitLocalVariableInstruction(o) is called before, because it is more generic.
 
 		if (stack().isEmpty()){ // Don't bother about 1 or 2 stack slots used. This check is implicitely done below while type checking.
 			constraintViolated(o, "Cannot STORE: Stack to read from is empty.");
 		}
 
 		if ( (!(o instanceof ASTORE)) ){
 			if (! (stack().peek() == o.getType(cpg)) ){// the other xSTORE types are singletons in BCEL.
 				constraintViolated(o, "Stack top type and STOREing Instruction type mismatch: Stack top: '"+stack().peek()+"'; Instruction type: '"+o.getType(cpg)+"'.");
 			}
 		}
 		else{ // we deal with ASTORE
 			Type stacktop = stack().peek();
 			if ( (!(stacktop instanceof ReferenceType)) && (!(stacktop instanceof ReturnaddressType)) ){
 				constraintViolated(o, "Stack top type and STOREing Instruction type mismatch: Stack top: '"+stack().peek()+"'; Instruction expects a ReferenceType or a ReturnadressType.");
 			}
 			//if (stacktop instanceof ReferenceType){
 			//	referenceTypeIsInitialized(o, (ReferenceType) stacktop);
 			//}
 		}
 	}
 
 	/***
 	 * Assures the generic preconditions of a ReturnInstruction instance.
 	 */
 	public void visitReturnInstruction(ReturnInstruction o){
 		Type method_type = mg.getType();
 		if (method_type == Type.BOOLEAN ||
 			method_type == Type.BYTE ||
 			method_type == Type.SHORT ||
 			method_type == Type.CHAR){
 		        method_type = Type.INT;
 			}
 
         if (o instanceof RETURN){
             if (method_type != Type.VOID){
                 constraintViolated(o, "RETURN instruction in non-void method.");
             }
             else{
 			    return;
             }
 		}
 		if (o instanceof ARETURN){
 			if (stack().peek() == Type.NULL){
 				return;
 			}
 			else{
 				if (! (stack().peek() instanceof ReferenceType)){
 					constraintViolated(o, "Reference type expected on top of stack, but is: '"+stack().peek()+"'.");
 				}
 				referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()));
 				//ReferenceType objectref = (ReferenceType) (stack().peek());
 				// TODO: This can only be checked if using Staerk-et-al's "set of object types" instead of a
 				// "wider cast object type" created during verification.
 				//if (! (objectref.isAssignmentCompatibleWith(mg.getType())) ){
 				//	constraintViolated(o, "Type on stack top which should be returned is a '"+stack().peek()+"' which is not assignment compatible with the return type of this method, '"+mg.getType()+"'.");
 				//}
 			}
 		}
 		else{
 			if (! ( method_type.equals( stack().peek() ))){
 				constraintViolated(o, "Current method has return type of '"+mg.getType()+"' expecting a '"+method_type+"' on top of the stack. But stack top is a '"+stack().peek()+"'.");
 			}
 		}
 	}
 
 	/****************************************************************/
 	/* "special"visitXXXX methods for one type of instruction each */
 	/****************************************************************/
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitAALOAD(AALOAD o){
 		Type arrayref = stack().peek(1);
 		Type index    = stack().peek(0);
 		
 		indexOfInt(o, index);
 		if (arrayrefOfArrayType(o, arrayref)){
 			if (! (((ArrayType) arrayref).getElementType() instanceof ReferenceType)){
 				constraintViolated(o, "The 'arrayref' does not refer to an array with elements of a ReferenceType but to an array of "+((ArrayType) arrayref).getElementType()+".");
 			}	
 			//referenceTypeIsInitialized(o, (ReferenceType) (((ArrayType) arrayref).getElementType()));
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitAASTORE(AASTORE o){
 	    try {
 		Type arrayref = stack().peek(2);
 		Type index    = stack().peek(1);
 		Type value    = stack().peek(0);
 
 		indexOfInt(o, index);
 		if (!(value instanceof ReferenceType)){
 			constraintViolated(o, "The 'value' is not of a ReferenceType but of type "+value+".");
 		}else{
 			//referenceTypeIsInitialized(o, (ReferenceType) value);
 		}
 		// Don't bother further with "referenceTypeIsInitialized()", there are no arrays
 		// of an uninitialized object type. 
 		if (arrayrefOfArrayType(o, arrayref)){
 			if (! (((ArrayType) arrayref).getElementType() instanceof ReferenceType)){
 				constraintViolated(o, "The 'arrayref' does not refer to an array with elements of a ReferenceType but to an array of "+((ArrayType) arrayref).getElementType()+".");
 			}
 			if (! ((ReferenceType)value).isAssignmentCompatibleWith((ReferenceType) ((ArrayType) arrayref).getElementType())){
 				constraintViolated(o, "The type of 'value' ('"+value+"') is not assignment compatible to the components of the array 'arrayref' refers to. ('"+((ArrayType) arrayref).getElementType()+"')");
 			}
 		}
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitACONST_NULL(ACONST_NULL o){
 		// Nothing needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitALOAD(ALOAD o){
 		//visitLoadInstruction(LoadInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitANEWARRAY(ANEWARRAY o){
 		if (!stack().peek().equals(Type.INT)) {
             constraintViolated(o, "The 'count' at the stack top is not of type '"+Type.INT+"' but of type '"+stack().peek()+"'.");
 		// The runtime constant pool item at that index must be a symbolic reference to a class,
 		// array, or interface type. See Pass 3a.
         }
 	}
 	
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitARETURN(ARETURN o){
 		if (! (stack().peek() instanceof ReferenceType) ){
 			constraintViolated(o, "The 'objectref' at the stack top is not of a ReferenceType but of type '"+stack().peek()+"'.");
 		}
 		ReferenceType objectref = (ReferenceType) (stack().peek());
 		referenceTypeIsInitialized(o, objectref);
 		
 		// The check below should already done via visitReturnInstruction(ReturnInstruction), see there.
 		// It cannot be done using Staerk-et-al's "set of object types" instead of a
 		// "wider cast object type", anyway.
 		//if (! objectref.isAssignmentCompatibleWith(mg.getReturnType() )){
 		//	constraintViolated(o, "The 'objectref' type "+objectref+" at the stack top is not assignment compatible with the return type '"+mg.getReturnType()+"' of the method.");
 		//}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitARRAYLENGTH(ARRAYLENGTH o){
 		Type arrayref = stack().peek(0);
 		arrayrefOfArrayType(o, arrayref);
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitASTORE(ASTORE o){
 		if (! ( (stack().peek() instanceof ReferenceType) || (stack().peek() instanceof ReturnaddressType) ) ){
 			constraintViolated(o, "The 'objectref' is not of a ReferenceType or of ReturnaddressType but of "+stack().peek()+".");
 		}
 		//if (stack().peek() instanceof ReferenceType){
 		//	referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
 		//}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitATHROW(ATHROW o){
 	    try {
 		// It's stated that 'objectref' must be of a ReferenceType --- but since Throwable is
 		// not derived from an ArrayType, it follows that 'objectref' must be of an ObjectType or Type.NULL.
 		if (! ((stack().peek() instanceof ObjectType) || (stack().peek().equals(Type.NULL))) ){
 			constraintViolated(o, "The 'objectref' is not of an (initialized) ObjectType but of type "+stack().peek()+".");
 		}
 		
 		// NULL is a subclass of every class, so to speak.
 		if (stack().peek().equals(Type.NULL)) {
             return;
         }
 				
 		ObjectType exc = (ObjectType) (stack().peek());
 		ObjectType throwable = (ObjectType) (Type.getType("Ljava/lang/Throwable;"));
 		if ( (! (exc.subclassOf(throwable)) ) && (! (exc.equals(throwable))) ){
 			constraintViolated(o, "The 'objectref' is not of class Throwable or of a subclass of Throwable, but of '"+stack().peek()+"'.");
 		}
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitBALOAD(BALOAD o){
 		Type arrayref = stack().peek(1);
 		Type index    = stack().peek(0);
 		indexOfInt(o, index);
 		if (arrayrefOfArrayType(o, arrayref)){
 			if (! ( (((ArrayType) arrayref).getElementType().equals(Type.BOOLEAN)) ||
 		 	       (((ArrayType) arrayref).getElementType().equals(Type.BYTE)) ) ){
 				constraintViolated(o, "The 'arrayref' does not refer to an array with elements of a Type.BYTE or Type.BOOLEAN but to an array of '"+((ArrayType) arrayref).getElementType()+"'.");
 			}
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitBASTORE(BASTORE o){
 		Type arrayref = stack().peek(2);
 		Type index    = stack().peek(1);
 		Type value    = stack().peek(0);
 
 		indexOfInt(o, index);
 		valueOfInt(o, value);
 		if (arrayrefOfArrayType(o, arrayref)){
 			if (! ( (((ArrayType) arrayref).getElementType().equals(Type.BOOLEAN)) ||
 			        (((ArrayType) arrayref).getElementType().equals(Type.BYTE)) ) ) {
                 constraintViolated(o, "The 'arrayref' does not refer to an array with elements of a Type.BYTE or Type.BOOLEAN but to an array of '"+((ArrayType) arrayref).getElementType()+"'.");
             }
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitBIPUSH(BIPUSH o){
 		// Nothing to do...
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitBREAKPOINT(BREAKPOINT o){
 		throw new AssertionViolatedException("In this JustIce verification pass there should not occur an illegal instruction such as BREAKPOINT.");
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitCALOAD(CALOAD o){
 		Type arrayref = stack().peek(1);
 		Type index = stack().peek(0);
 		
 		indexOfInt(o, index);
 		arrayrefOfArrayType(o, arrayref);
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitCASTORE(CASTORE o){
 		Type arrayref = stack().peek(2);
 		Type index = stack().peek(1);
 		Type value = stack().peek(0);
 		
 		indexOfInt(o, index);
 		valueOfInt(o, value);
 		if (arrayrefOfArrayType(o, arrayref)){
 			if (! ((ArrayType) arrayref).getElementType().equals(Type.CHAR) ){
 				constraintViolated(o, "The 'arrayref' does not refer to an array with elements of type char but to an array of type "+((ArrayType) arrayref).getElementType()+".");
 			}
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitCHECKCAST(CHECKCAST o){
 		// The objectref must be of type reference.
 		Type objectref = stack().peek(0);
 		if (!(objectref instanceof ReferenceType)){
 			constraintViolated(o, "The 'objectref' is not of a ReferenceType but of type "+objectref+".");
 		}
 		//else{
 		//	referenceTypeIsInitialized(o, (ReferenceType) objectref);
 		//}
 		// The unsigned indexbyte1 and indexbyte2 are used to construct an index into the runtime constant pool of the
 		// current class (ß3.6), where the value of the index is (indexbyte1 << 8) | indexbyte2. The runtime constant
 		// pool item at the index must be a symbolic reference to a class, array, or interface type.
 		Constant c = cpg.getConstant(o.getIndex());
 		if (! (c instanceof ConstantClass)){
 			constraintViolated(o, "The Constant at 'index' is not a ConstantClass, but '"+c+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitD2F(D2F o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitD2I(D2I o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitD2L(D2L o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDADD(DADD o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDALOAD(DALOAD o){
 		indexOfInt(o, stack().peek());
 		if (stack().peek(1) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(1) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-top must be of type double[] but is '"+stack().peek(1)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(1))).getBasicType();
 		if (t != Type.DOUBLE){
 			constraintViolated(o, "Stack next-to-top must be of type double[] but is '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDASTORE(DASTORE o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		indexOfInt(o, stack().peek(1));
 		if (stack().peek(2) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(2) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type double[] but is '"+stack().peek(2)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(2))).getBasicType();
 		if (t != Type.DOUBLE){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type double[] but is '"+stack().peek(2)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDCMPG(DCMPG o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDCMPL(DCMPL o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDCONST(DCONST o){
 		// There's nothing to be done here.
 	}
 	
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDDIV(DDIV o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDLOAD(DLOAD o){
 		//visitLoadInstruction(LoadInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDMUL(DMUL o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDNEG(DNEG o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDREM(DREM o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDRETURN(DRETURN o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDSTORE(DSTORE o){
 		//visitStoreInstruction(StoreInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDSUB(DSUB o){
 		if (stack().peek() != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.DOUBLE){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDUP(DUP o){
 		if (stack().peek().getSize() != 1){
 			constraintViolated(o, "Won't DUP type on stack top '"+stack().peek()+"' because it must occupy exactly one slot, not '"+stack().peek().getSize()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDUP_X1(DUP_X1 o){
 		if (stack().peek().getSize() != 1){
 			constraintViolated(o, "Type on stack top '"+stack().peek()+"' should occupy exactly one slot, not '"+stack().peek().getSize()+"'.");
 		}
 		if (stack().peek(1).getSize() != 1){
 			constraintViolated(o, "Type on stack next-to-top '"+stack().peek(1)+"' should occupy exactly one slot, not '"+stack().peek(1).getSize()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDUP_X2(DUP_X2 o){
 		if (stack().peek().getSize() != 1){
 			constraintViolated(o, "Stack top type must be of size 1, but is '"+stack().peek()+"' of size '"+stack().peek().getSize()+"'.");
 		}
 		if (stack().peek(1).getSize() == 2){
 			return; // Form 2, okay.
 		}
 		else{   //stack().peek(1).getSize == 1.
 			if (stack().peek(2).getSize() != 1){
 				constraintViolated(o, "If stack top's size is 1 and stack next-to-top's size is 1, stack next-to-next-to-top's size must also be 1, but is: '"+stack().peek(2)+"' of size '"+stack().peek(2).getSize()+"'.");
 			}
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDUP2(DUP2 o){
 		if (stack().peek().getSize() == 2){
 			return; // Form 2, okay.
 		}
 		else{ //stack().peek().getSize() == 1.
 			if (stack().peek(1).getSize() != 1){
 				constraintViolated(o, "If stack top's size is 1, then stack next-to-top's size must also be 1. But it is '"+stack().peek(1)+"' of size '"+stack().peek(1).getSize()+"'.");
 			}
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDUP2_X1(DUP2_X1 o){
 		if (stack().peek().getSize() == 2){
 			if (stack().peek(1).getSize() != 1){
 				constraintViolated(o, "If stack top's size is 2, then stack next-to-top's size must be 1. But it is '"+stack().peek(1)+"' of size '"+stack().peek(1).getSize()+"'.");
 			}
 			else{
 				return; // Form 2
 			}
 		}
 		else{ // stack top is of size 1
 			if ( stack().peek(1).getSize() != 1 ){
 				constraintViolated(o, "If stack top's size is 1, then stack next-to-top's size must also be 1. But it is '"+stack().peek(1)+"' of size '"+stack().peek(1).getSize()+"'.");
 			}
 			if ( stack().peek(2).getSize() != 1 ){
 				constraintViolated(o, "If stack top's size is 1, then stack next-to-next-to-top's size must also be 1. But it is '"+stack().peek(2)+"' of size '"+stack().peek(2).getSize()+"'.");
 			}
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitDUP2_X2(DUP2_X2 o){
 
 		if (stack().peek(0).getSize() == 2){
 		 	if (stack().peek(1).getSize() == 2){
 				return; // Form 4
 			}
 			else{// stack top size is 2, next-to-top's size is 1
 				if ( stack().peek(2).getSize() != 1 ){
 					constraintViolated(o, "If stack top's size is 2 and stack-next-to-top's size is 1, then stack next-to-next-to-top's size must also be 1. But it is '"+stack().peek(2)+"' of size '"+stack().peek(2).getSize()+"'.");
 				}
 				else{
 					return; // Form 2
 				}
 			}
 		}
 		else{// stack top is of size 1
 			if (stack().peek(1).getSize() == 1){
 				if ( stack().peek(2).getSize() == 2 ){
 					return; // Form 3
 				}
 				else{
 					if ( stack().peek(3).getSize() == 1){
 						return; // Form 1
 					}
 				}
 			}
 		}
 		constraintViolated(o, "The operand sizes on the stack do not match any of the four forms of usage of this instruction.");
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitF2D(F2D o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitF2I(F2I o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitF2L(F2L o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 	}
 	
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFADD(FADD o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.FLOAT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFALOAD(FALOAD o){
 		indexOfInt(o, stack().peek());
 		if (stack().peek(1) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(1) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-top must be of type float[] but is '"+stack().peek(1)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(1))).getBasicType();
 		if (t != Type.FLOAT){
 			constraintViolated(o, "Stack next-to-top must be of type float[] but is '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFASTORE(FASTORE o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		indexOfInt(o, stack().peek(1));
 		if (stack().peek(2) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(2) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type float[] but is '"+stack().peek(2)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(2))).getBasicType();
 		if (t != Type.FLOAT){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type float[] but is '"+stack().peek(2)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFCMPG(FCMPG o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.FLOAT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFCMPL(FCMPL o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.FLOAT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFCONST(FCONST o){
 		// nothing to do here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFDIV(FDIV o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.FLOAT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFLOAD(FLOAD o){
 		//visitLoadInstruction(LoadInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFMUL(FMUL o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.FLOAT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFNEG(FNEG o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFREM(FREM o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.FLOAT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFRETURN(FRETURN o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFSTORE(FSTORE o){
 		//visitStoreInstruction(StoreInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitFSUB(FSUB o){
 		if (stack().peek() != Type.FLOAT){
 			constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.FLOAT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitGETFIELD(GETFIELD o){
 	    try {
 		Type objectref = stack().peek();
 		if (! ( (objectref instanceof ObjectType) || (objectref == Type.NULL) ) ){
 			constraintViolated(o, "Stack top should be an object reference that's not an array reference, but is '"+objectref+"'.");
 		}
 		
 		String field_name = o.getFieldName(cpg);
 		
 		JavaClass jc = Repository.lookupClass(o.getClassType(cpg).getClassName());
 		Field[] fields = jc.getFields();
 		Field f = null;
 		for (int i=0; i<fields.length; i++){
 			if (fields[i].getName().equals(field_name)){
 				  Type f_type = Type.getType(fields[i].getSignature());
 				  Type o_type = o.getType(cpg);
 					/* TODO: Check if assignment compatibility is sufficient.
 				   * What does Sun do?
 				   */
 				  if (f_type.equals(o_type)){
 						f = fields[i];
 						break;
 					}
 			}
 		}
 
 		if (f == null){
 			JavaClass[] superclasses = jc.getSuperClasses();
 			outer: 
 			for (int j=0; j<superclasses.length; j++){
 				fields = superclasses[j].getFields();
 				for (int i=0; i<fields.length; i++){
 					if (fields[i].getName().equals(field_name)){
 						Type f_type = Type.getType(fields[i].getSignature());
 						Type o_type = o.getType(cpg);
 						if (f_type.equals(o_type)){
 							f = fields[i];
 							if ((f.getAccessFlags() & (Constants.ACC_PUBLIC | Constants.ACC_PROTECTED)) == 0) {
                                 f = null;
                             }
 							break outer;
 						}
 					}
 				}
 			}
 			if (f == null) {
                 throw new AssertionViolatedException("Field '"+field_name+"' not found?!?");
             }
 		}
 
 		if (f.isProtected()){
 			ObjectType classtype = o.getClassType(cpg);
 			ObjectType curr = new ObjectType(mg.getClassName());
 
 			if (	classtype.equals(curr) ||
 						curr.subclassOf(classtype)	){
 				Type t = stack().peek();
 				if (t == Type.NULL){
 					return;
 				}
 				if (! (t instanceof ObjectType) ){
 					constraintViolated(o, "The 'objectref' must refer to an object that's not an array. Found instead: '"+t+"'.");
 				}
 				ObjectType objreftype = (ObjectType) t;
 				if (! ( objreftype.equals(curr) ||
 						    objreftype.subclassOf(curr) ) ){
 					//TODO: One day move to Staerk-et-al's "Set of object types" instead of "wider" object types
 					//      created during the verification.
 					//      "Wider" object types don't allow us to check for things like that below.
 					//constraintViolated(o, "The referenced field has the ACC_PROTECTED modifier, and it's a member of the current class or a superclass of the current class. However, the referenced object type '"+stack().peek()+"' is not the current class or a subclass of the current class.");
 				}
 			} 
 		}
 		
 		// TODO: Could go into Pass 3a.
 		if (f.isStatic()){
 			constraintViolated(o, "Referenced field '"+f+"' is static which it shouldn't be.");
 		}
 
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitGETSTATIC(GETSTATIC o){
 		// Field must be static: see Pass 3a.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitGOTO(GOTO o){
 		// nothing to do here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitGOTO_W(GOTO_W o){
 		// nothing to do here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitI2B(I2B o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitI2C(I2C o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitI2D(I2D o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitI2F(I2F o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitI2L(I2L o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitI2S(I2S o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIADD(IADD o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIALOAD(IALOAD o){
 		indexOfInt(o, stack().peek());
 		if (stack().peek(1) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(1) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-top must be of type int[] but is '"+stack().peek(1)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(1))).getBasicType();
 		if (t != Type.INT){
 			constraintViolated(o, "Stack next-to-top must be of type int[] but is '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIAND(IAND o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIASTORE(IASTORE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		indexOfInt(o, stack().peek(1));
 		if (stack().peek(2) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(2) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type int[] but is '"+stack().peek(2)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(2))).getBasicType();
 		if (t != Type.INT){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type int[] but is '"+stack().peek(2)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitICONST(ICONST o){
 		//nothing to do here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIDIV(IDIV o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ACMPEQ(IF_ACMPEQ o){
 		if (!(stack().peek() instanceof ReferenceType)){
 			constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
 		}
 		//referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
 	
 		if (!(stack().peek(1) instanceof ReferenceType)){
 			constraintViolated(o, "The value at the stack next-to-top is not of a ReferenceType, but of type '"+stack().peek(1)+"'.");
 		}
 		//referenceTypeIsInitialized(o, (ReferenceType) (stack().peek(1)) );
 		
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ACMPNE(IF_ACMPNE o){
 		if (!(stack().peek() instanceof ReferenceType)){
 			constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
 			//referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
 		}
 		if (!(stack().peek(1) instanceof ReferenceType)){
 			constraintViolated(o, "The value at the stack next-to-top is not of a ReferenceType, but of type '"+stack().peek(1)+"'.");
 			//referenceTypeIsInitialized(o, (ReferenceType) (stack().peek(1)) );
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ICMPEQ(IF_ICMPEQ o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ICMPGE(IF_ICMPGE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ICMPGT(IF_ICMPGT o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ICMPLE(IF_ICMPLE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ICMPLT(IF_ICMPLT o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIF_ICMPNE(IF_ICMPNE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFEQ(IFEQ o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFGE(IFGE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFGT(IFGT o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFLE(IFLE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFLT(IFLT o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFNE(IFNE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFNONNULL(IFNONNULL o){
 		if (!(stack().peek() instanceof ReferenceType)){
 			constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
 		}
 		referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );	
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIFNULL(IFNULL o){
 		if (!(stack().peek() instanceof ReferenceType)){
 			constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
 		}
 		referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );	
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIINC(IINC o){
 		// Mhhh. In BCEL, at this time "IINC" is not a LocalVariableInstruction.
 		if (locals().maxLocals() <= (o.getType(cpg).getSize()==1? o.getIndex() : o.getIndex()+1) ){
 			constraintViolated(o, "The 'index' is not a valid index into the local variable array.");
 		}
 
 		indexOfInt(o, locals().get(o.getIndex()));
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitILOAD(ILOAD o){
 		// All done by visitLocalVariableInstruction(), visitLoadInstruction()
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIMPDEP1(IMPDEP1 o){
 		throw new AssertionViolatedException("In this JustIce verification pass there should not occur an illegal instruction such as IMPDEP1.");
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIMPDEP2(IMPDEP2 o){
 		throw new AssertionViolatedException("In this JustIce verification pass there should not occur an illegal instruction such as IMPDEP2.");
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIMUL(IMUL o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitINEG(INEG o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitINSTANCEOF(INSTANCEOF o){
 		// The objectref must be of type reference.
 		Type objectref = stack().peek(0);
 		if (!(objectref instanceof ReferenceType)){
 			constraintViolated(o, "The 'objectref' is not of a ReferenceType but of type "+objectref+".");
 		}
 		//else{
 		//	referenceTypeIsInitialized(o, (ReferenceType) objectref);
 		//}
 		// The unsigned indexbyte1 and indexbyte2 are used to construct an index into the runtime constant pool of the
 		// current class (ß3.6), where the value of the index is (indexbyte1 << 8) | indexbyte2. The runtime constant
 		// pool item at the index must be a symbolic reference to a class, array, or interface type.
 		Constant c = cpg.getConstant(o.getIndex());
 		if (! (c instanceof ConstantClass)){
 			constraintViolated(o, "The Constant at 'index' is not a ConstantClass, but '"+c+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitINVOKEINTERFACE(INVOKEINTERFACE o){
 		// Method is not native, otherwise pass 3 would not happen.
 		
 		int count = o.getCount();
 		if (count == 0){
 			constraintViolated(o, "The 'count' argument must not be 0.");
 		}
 		// It is a ConstantInterfaceMethodref, Pass 3a made it sure.
 		// TODO: Do we want to do anything with it?
         //ConstantInterfaceMethodref cimr = (ConstantInterfaceMethodref) (cpg.getConstant(o.getIndex()));
 		
 		// the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
 
 		Type t = o.getType(cpg);
 		if (t instanceof ObjectType){
 			String name = ((ObjectType)t).getClassName();
 			Verifier v = VerifierFactory.getVerifier( name );
 			VerificationResult vr = v.doPass2();
 			if (vr.getStatus() != VerificationResult.VERIFIED_OK){
 				constraintViolated((Instruction) o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
 			}
 		}
 
 
 		Type[] argtypes = o.getArgumentTypes(cpg);
 		int nargs = argtypes.length;
 		
 		for (int i=nargs-1; i>=0; i--){
 			Type fromStack = stack().peek( (nargs-1) - i );	// 0 to nargs-1
 			Type fromDesc = argtypes[i];
 			if (fromDesc == Type.BOOLEAN ||
 					fromDesc == Type.BYTE ||
 					fromDesc == Type.CHAR ||
 					fromDesc == Type.SHORT){
 				fromDesc = Type.INT;
 			}
 			if (! fromStack.equals(fromDesc)){
 				if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType){
 					ReferenceType rFromStack = (ReferenceType) fromStack;
 					//ReferenceType rFromDesc = (ReferenceType) fromDesc;
 					// TODO: This can only be checked when using Staerk-et-al's "set of object types"
 					// instead of a "wider cast object type" created during verification.
 					//if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ){
 					//	constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack (which is not assignment compatible).");
 					//}
                     referenceTypeIsInitialized(o, rFromStack);
 				}
 				else{
 					constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
 				}
 			}
 		}
 		
 		Type objref = stack().peek(nargs);
 		if (objref == Type.NULL){
 			return;
 		}
 		if (! (objref instanceof ReferenceType) ){
 			constraintViolated(o, "Expecting a reference type as 'objectref' on the stack, not a '"+objref+"'.");
 		}
 		referenceTypeIsInitialized(o, (ReferenceType) objref);
 		if (!(objref instanceof ObjectType)){
 			if (!(objref instanceof ArrayType)){
 				constraintViolated(o, "Expecting an ObjectType as 'objectref' on the stack, not a '"+objref+"'."); // could be a ReturnaddressType
 			}
 			else{
 				objref = GENERIC_ARRAY;
 			}
 		}
 		
 		// String objref_classname = ((ObjectType) objref).getClassName();
 	    // String theInterface = o.getClassName(cpg);
 		// TODO: This can only be checked if we're using Staerk-et-al's "set of object types"
 		//       instead of "wider cast object types" generated during verification.
 		//if ( ! Repository.implementationOf(objref_classname, theInterface) ){
 		//	constraintViolated(o, "The 'objref' item '"+objref+"' does not implement '"+theInterface+"' as expected.");
 		//}	
 
 		int counted_count = 1; // 1 for the objectref
 		for (int i=0; i<nargs; i++){
 			counted_count += argtypes[i].getSize();
 		}
 		if (count != counted_count){
 			constraintViolated(o, "The 'count' argument should probably read '"+counted_count+"' but is '"+count+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitINVOKESPECIAL(INVOKESPECIAL o){
 	    try {
 		// Don't init an object twice.
 		if ( (o.getMethodName(cpg).equals(Constants.CONSTRUCTOR_NAME)) && (!(stack().peek(o.getArgumentTypes(cpg).length) instanceof UninitializedObjectType)) ){
 			constraintViolated(o, "Possibly initializing object twice. A valid instruction sequence must not have an uninitialized object on the operand stack or in a local variable during a backwards branch, or in a local variable in code protected by an exception handler. Please see The Java Virtual Machine Specification, Second Edition, 4.9.4 (pages 147 and 148) for details.");
 		}
 
 		// the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
 
 		Type t = o.getType(cpg);
 		if (t instanceof ObjectType){
 			String name = ((ObjectType)t).getClassName();
 			Verifier v = VerifierFactory.getVerifier( name );
 			VerificationResult vr = v.doPass2();
 			if (vr.getStatus() != VerificationResult.VERIFIED_OK){
 				constraintViolated((Instruction) o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
 			}
 		}
 
 
 		Type[] argtypes = o.getArgumentTypes(cpg);
 		int nargs = argtypes.length;
 		
 		for (int i=nargs-1; i>=0; i--){
 			Type fromStack = stack().peek( (nargs-1) - i );	// 0 to nargs-1
 			Type fromDesc = argtypes[i];
 			if (fromDesc == Type.BOOLEAN ||
 					fromDesc == Type.BYTE ||
 					fromDesc == Type.CHAR ||
 					fromDesc == Type.SHORT){
 				fromDesc = Type.INT;
 			}
 			if (! fromStack.equals(fromDesc)){
 				if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType){
 					ReferenceType rFromStack = (ReferenceType) fromStack;
 					ReferenceType rFromDesc = (ReferenceType) fromDesc;
 					// TODO: This can only be checked using Staerk-et-al's "set of object types", not
 					// using a "wider cast object type".
 					if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ){
 						constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack (which is not assignment compatible).");
 					}
                     referenceTypeIsInitialized(o, rFromStack);
 				}
 				else{
 					constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
 				}
 			}
 		}
 		
 		Type objref = stack().peek(nargs);
 		if (objref == Type.NULL){
 			return;
 		}
 		if (! (objref instanceof ReferenceType) ){
 			constraintViolated(o, "Expecting a reference type as 'objectref' on the stack, not a '"+objref+"'.");
 		}
 		String objref_classname = null;
 		if ( !(o.getMethodName(cpg).equals(Constants.CONSTRUCTOR_NAME))){
 			referenceTypeIsInitialized(o, (ReferenceType) objref);
 			if (!(objref instanceof ObjectType)){
 				if (!(objref instanceof ArrayType)){
 					constraintViolated(o, "Expecting an ObjectType as 'objectref' on the stack, not a '"+objref+"'."); // could be a ReturnaddressType
 				}
 				else{
 					objref = GENERIC_ARRAY;
 				}
 			}
 
 			objref_classname = ((ObjectType) objref).getClassName();		
 		}
 		else{
 			if (!(objref instanceof UninitializedObjectType)){
 				constraintViolated(o, "Expecting an UninitializedObjectType as 'objectref' on the stack, not a '"+objref+"'. Otherwise, you couldn't invoke a method since an array has no methods (not to speak of a return address).");
 			}
 			objref_classname = ((UninitializedObjectType) objref).getInitialized().getClassName();
 		}
 		
 
 		String theClass = o.getClassName(cpg);
 		if ( ! Repository.instanceOf(objref_classname, theClass) ){
 			constraintViolated(o, "The 'objref' item '"+objref+"' does not implement '"+theClass+"' as expected.");
 		}	
 		
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitINVOKESTATIC(INVOKESTATIC o){
 	    try {
 		// Method is not native, otherwise pass 3 would not happen.
 		
 		Type t = o.getType(cpg);
 		if (t instanceof ObjectType){
 			String name = ((ObjectType)t).getClassName();
 			Verifier v = VerifierFactory.getVerifier( name );
 			VerificationResult vr = v.doPass2();
 			if (vr.getStatus() != VerificationResult.VERIFIED_OK){
 				constraintViolated((Instruction) o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
 			}
 		}
 
 		Type[] argtypes = o.getArgumentTypes(cpg);
 		int nargs = argtypes.length;
 		
 		for (int i=nargs-1; i>=0; i--){
 			Type fromStack = stack().peek( (nargs-1) - i );	// 0 to nargs-1
 			Type fromDesc = argtypes[i];
 			if (fromDesc == Type.BOOLEAN ||
 					fromDesc == Type.BYTE ||
 					fromDesc == Type.CHAR ||
 					fromDesc == Type.SHORT){
 				fromDesc = Type.INT;
 			}
 			if (! fromStack.equals(fromDesc)){
 				if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType){
 					ReferenceType rFromStack = (ReferenceType) fromStack;
 					ReferenceType rFromDesc = (ReferenceType) fromDesc;
 					// TODO: This check can possibly only be done using Staerk-et-al's "set of object types"
 					// instead of a "wider cast object type" created during verification.
 					if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ){
 						constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack (which is not assignment compatible).");
 					}
                     referenceTypeIsInitialized(o, rFromStack);
 				}
 				else{
 					constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
 				}
 			}
 		}
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitINVOKEVIRTUAL(INVOKEVIRTUAL o){
 	    try {
 		// the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
 
 		Type t = o.getType(cpg);
 		if (t instanceof ObjectType){
 			String name = ((ObjectType)t).getClassName();
 			Verifier v = VerifierFactory.getVerifier( name );
 			VerificationResult vr = v.doPass2();
 			if (vr.getStatus() != VerificationResult.VERIFIED_OK){
 				constraintViolated((Instruction) o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
 			}
 		}
 
 
 		Type[] argtypes = o.getArgumentTypes(cpg);
 		int nargs = argtypes.length;
 		
 		for (int i=nargs-1; i>=0; i--){
 			Type fromStack = stack().peek( (nargs-1) - i );	// 0 to nargs-1
 			Type fromDesc = argtypes[i];
 			if (fromDesc == Type.BOOLEAN ||
 					fromDesc == Type.BYTE ||
 					fromDesc == Type.CHAR ||
 					fromDesc == Type.SHORT){
 				fromDesc = Type.INT;
 			}
 			if (! fromStack.equals(fromDesc)){
 				if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType){
 					ReferenceType rFromStack = (ReferenceType) fromStack;
 					ReferenceType rFromDesc = (ReferenceType) fromDesc;
 					// TODO: This can possibly only be checked when using Staerk-et-al's "set of object types" instead
 					// of a single "wider cast object type" created during verification.
 					if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ){
 						constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack (which is not assignment compatible).");
 					}
                     referenceTypeIsInitialized(o, rFromStack);
 				}
 				else{
 					constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
 				}
 			}
 		}
 		
 		Type objref = stack().peek(nargs);
 		if (objref == Type.NULL){
 			return;
 		}
 		if (! (objref instanceof ReferenceType) ){
 			constraintViolated(o, "Expecting a reference type as 'objectref' on the stack, not a '"+objref+"'.");
 		}
 		referenceTypeIsInitialized(o, (ReferenceType) objref);
 		if (!(objref instanceof ObjectType)){
 			if (!(objref instanceof ArrayType)){
 				constraintViolated(o, "Expecting an ObjectType as 'objectref' on the stack, not a '"+objref+"'."); // could be a ReturnaddressType
 			}
 			else{
 				objref = GENERIC_ARRAY;
 			}
 		}
 		
 		String objref_classname = ((ObjectType) objref).getClassName();
 
 		String theClass = o.getClassName(cpg);
 	
 		if ( ! Repository.instanceOf(objref_classname, theClass) ){
 			constraintViolated(o, "The 'objref' item '"+objref+"' does not implement '"+theClass+"' as expected.");
 		}	
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIOR(IOR o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIREM(IREM o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIRETURN(IRETURN o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitISHL(ISHL o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitISHR(ISHR o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitISTORE(ISTORE o){
 		//visitStoreInstruction(StoreInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitISUB(ISUB o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIUSHR(IUSHR o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitIXOR(IXOR o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.INT){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitJSR(JSR o){
 		// nothing to do here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitJSR_W(JSR_W o){
 		// nothing to do here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitL2D(L2D o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitL2F(L2F o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitL2I(L2I o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLADD(LADD o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLALOAD(LALOAD o){
 		indexOfInt(o, stack().peek());
 		if (stack().peek(1) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(1) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-top must be of type long[] but is '"+stack().peek(1)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(1))).getBasicType();
 		if (t != Type.LONG){
 			constraintViolated(o, "Stack next-to-top must be of type long[] but is '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLAND(LAND o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLASTORE(LASTORE o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		indexOfInt(o, stack().peek(1));
 		if (stack().peek(2) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(2) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type long[] but is '"+stack().peek(2)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(2))).getBasicType();
 		if (t != Type.LONG){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type long[] but is '"+stack().peek(2)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLCMP(LCMP o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLCONST(LCONST o){
 		// Nothing to do here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLDC(LDC o){
 		// visitCPInstruction is called first.
 		
 		Constant c = cpg.getConstant(o.getIndex());
 		if 	(!	(	( c instanceof ConstantInteger) ||
 							( c instanceof ConstantFloat	)	||
 							( c instanceof ConstantString )	)	){
 			constraintViolated(o, "Referenced constant should be a CONSTANT_Integer, a CONSTANT_Float or a CONSTANT_String, but is '"+c+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLDC_W(LDC_W o){
 		// visitCPInstruction is called first.
 		
 		Constant c = cpg.getConstant(o.getIndex());
 		if 	(!	(	( c instanceof ConstantInteger) ||
 							( c instanceof ConstantFloat	)	||
 							( c instanceof ConstantString )	)	){
 			constraintViolated(o, "Referenced constant should be a CONSTANT_Integer, a CONSTANT_Float or a CONSTANT_String, but is '"+c+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLDC2_W(LDC2_W o){
 		// visitCPInstruction is called first.
 		
 		Constant c = cpg.getConstant(o.getIndex());
 		if 	(!	(	( c instanceof ConstantLong) ||
 							( c instanceof ConstantDouble )	)	){
 			constraintViolated(o, "Referenced constant should be a CONSTANT_Integer, a CONSTANT_Float or a CONSTANT_String, but is '"+c+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLDIV(LDIV o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLLOAD(LLOAD o){
 		//visitLoadInstruction(LoadInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLMUL(LMUL o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLNEG(LNEG o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 	}
 	
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLOOKUPSWITCH(LOOKUPSWITCH o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		// See also pass 3a.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLOR(LOR o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLREM(LREM o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLRETURN(LRETURN o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLSHL(LSHL o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLSHR(LSHR o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLSTORE(LSTORE o){
 		//visitStoreInstruction(StoreInstruction) is called before.
 		
 		// Nothing else needs to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLSUB(LSUB o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLUSHR(LUSHR o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitLXOR(LXOR o){
 		if (stack().peek() != Type.LONG){
 			constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
 		}
 		if (stack().peek(1) != Type.LONG){
 			constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitMONITORENTER(MONITORENTER o){
 		if (! ((stack().peek()) instanceof ReferenceType)){
 			constraintViolated(o, "The stack top should be of a ReferenceType, but is '"+stack().peek()+"'.");
 		}
 		//referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitMONITOREXIT(MONITOREXIT o){
 		if (! ((stack().peek()) instanceof ReferenceType)){
 			constraintViolated(o, "The stack top should be of a ReferenceType, but is '"+stack().peek()+"'.");
 		}
 		//referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitMULTIANEWARRAY(MULTIANEWARRAY o){
 		int dimensions = o.getDimensions();
 		// Dimensions argument is okay: see Pass 3a.
 		for (int i=0; i<dimensions; i++){
 			if (stack().peek(i) != Type.INT){
 				constraintViolated(o, "The '"+dimensions+"' upper stack types should be 'int' but aren't.");
 			}
 		}
 		// The runtime constant pool item at that index must be a symbolic reference to a class,
 		// array, or interface type. See Pass 3a.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitNEW(NEW o){
 		//visitCPInstruction(CPInstruction) has been called before.
 		//visitLoadClass(LoadClass) has been called before.
 		
 		Type t = o.getType(cpg);
 		if (! (t instanceof ReferenceType)){
 			throw new AssertionViolatedException("NEW.getType() returning a non-reference type?!");
 		}
 		if (! (t instanceof ObjectType)){
 			constraintViolated(o, "Expecting a class type (ObjectType) to work on. Found: '"+t+"'.");
 		}
 		ObjectType obj = (ObjectType) t;
 
 		//e.g.: Don't instantiate interfaces
 		if (! obj.referencesClass()){
 			constraintViolated(o, "Expecting a class type (ObjectType) to work on. Found: '"+obj+"'.");
 		}		
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitNEWARRAY(NEWARRAY o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitNOP(NOP o){
 		// nothing is to be done here.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitPOP(POP o){
 		if (stack().peek().getSize() != 1){
 			constraintViolated(o, "Stack top size should be 1 but stack top is '"+stack().peek()+"' of size '"+stack().peek().getSize()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitPOP2(POP2 o){
 		if (stack().peek().getSize() != 2){
 			constraintViolated(o, "Stack top size should be 2 but stack top is '"+stack().peek()+"' of size '"+stack().peek().getSize()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitPUTFIELD(PUTFIELD o){
 	    try {
 
 		Type objectref = stack().peek(1);
 		if (! ( (objectref instanceof ObjectType) || (objectref == Type.NULL) ) ){
 			constraintViolated(o, "Stack next-to-top should be an object reference that's not an array reference, but is '"+objectref+"'.");
 		}
 		
 		String field_name = o.getFieldName(cpg);
 		
 		JavaClass jc = Repository.lookupClass(o.getClassType(cpg).getClassName());
 		Field[] fields = jc.getFields();
 		Field f = null;
 		for (int i=0; i<fields.length; i++){
 			if (fields[i].getName().equals(field_name)){
 				  Type f_type = Type.getType(fields[i].getSignature());
 				  Type o_type = o.getType(cpg);
 					/* TODO: Check if assignment compatibility is sufficient.
 				   * What does Sun do?
 				   */
 				  if (f_type.equals(o_type)){
 						f = fields[i];
 						break;
 					}
 			}
 		}
 		if (f == null){
 			throw new AssertionViolatedException("Field not found?!?");
 		}
 
 		Type value = stack().peek();
 		Type t = Type.getType(f.getSignature());
 		Type shouldbe = t;
 		if (shouldbe == Type.BOOLEAN ||
 				shouldbe == Type.BYTE ||
 				shouldbe == Type.CHAR ||
 				shouldbe == Type.SHORT){
 			shouldbe = Type.INT;
 		}
 		if (t instanceof ReferenceType){
 			ReferenceType rvalue = null;
 			if (value instanceof ReferenceType){
 				rvalue = (ReferenceType) value;
 				referenceTypeIsInitialized(o, rvalue);
 			}
 			else{
 				constraintViolated(o, "The stack top type '"+value+"' is not of a reference type as expected.");
 			}
 			// TODO: This can possibly only be checked using Staerk-et-al's "set-of-object types", not
 			// using "wider cast object types" created during verification.
 			// Comment it out if you encounter problems. See also the analogon at visitPUTSTATIC.
 			if (!(rvalue.isAssignmentCompatibleWith(shouldbe))){
 				constraintViolated(o, "The stack top type '"+value+"' is not assignment compatible with '"+shouldbe+"'.");
 			}
 		}
 		else{
 			if (shouldbe != value){
 				constraintViolated(o, "The stack top type '"+value+"' is not of type '"+shouldbe+"' as expected.");
 			}
 		}
 		
 		if (f.isProtected()){
 			ObjectType classtype = o.getClassType(cpg);
 			ObjectType curr = new ObjectType(mg.getClassName());
 
 			if (	classtype.equals(curr) ||
 						curr.subclassOf(classtype)	){
 				Type tp = stack().peek(1);
 				if (tp == Type.NULL){
 					return;
 				}
 				if (! (tp instanceof ObjectType) ){
 					constraintViolated(o, "The 'objectref' must refer to an object that's not an array. Found instead: '"+tp+"'.");
 				}
 				ObjectType objreftype = (ObjectType) tp;
 				if (! ( objreftype.equals(curr) ||
 						    objreftype.subclassOf(curr) ) ){
 					constraintViolated(o, "The referenced field has the ACC_PROTECTED modifier, and it's a member of the current class or a superclass of the current class. However, the referenced object type '"+stack().peek()+"' is not the current class or a subclass of the current class.");
 				}
 			} 
 		}
 
 		// TODO: Could go into Pass 3a.
 		if (f.isStatic()){
 			constraintViolated(o, "Referenced field '"+f+"' is static which it shouldn't be.");
 		}
 
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitPUTSTATIC(PUTSTATIC o){
 	    try {
 		String field_name = o.getFieldName(cpg);
 		JavaClass jc = Repository.lookupClass(o.getClassType(cpg).getClassName());
 		Field[] fields = jc.getFields();
 		Field f = null;
 		for (int i=0; i<fields.length; i++){
 			if (fields[i].getName().equals(field_name)){
 					Type f_type = Type.getType(fields[i].getSignature());
 				  Type o_type = o.getType(cpg);
 					/* TODO: Check if assignment compatibility is sufficient.
 				   * What does Sun do?
 				   */
 				  if (f_type.equals(o_type)){
 						f = fields[i];
 						break;
 					}
 			}
 		}
 		if (f == null){
 			throw new AssertionViolatedException("Field not found?!?");
 		}
 		Type value = stack().peek();
 		Type t = Type.getType(f.getSignature());
 		Type shouldbe = t;
 		if (shouldbe == Type.BOOLEAN ||
 				shouldbe == Type.BYTE ||
 				shouldbe == Type.CHAR ||
 				shouldbe == Type.SHORT){
 			shouldbe = Type.INT;
 		}
 		if (t instanceof ReferenceType){
 			ReferenceType rvalue = null;
 			if (value instanceof ReferenceType){
 				rvalue = (ReferenceType) value;
 				referenceTypeIsInitialized(o, rvalue);
 			}
 			else{
 				constraintViolated(o, "The stack top type '"+value+"' is not of a reference type as expected.");
 			}
 			// TODO: This can possibly only be checked using Staerk-et-al's "set-of-object types", not
 			// using "wider cast object types" created during verification.
 			// Comment it out if you encounter problems. See also the analogon at visitPUTFIELD.
 			if (!(rvalue.isAssignmentCompatibleWith(shouldbe))){
 				constraintViolated(o, "The stack top type '"+value+"' is not assignment compatible with '"+shouldbe+"'.");
 			}
 		}
 		else{
 			if (shouldbe != value){
 				constraintViolated(o, "The stack top type '"+value+"' is not of type '"+shouldbe+"' as expected.");
 			}
 		}
 		// TODO: Interface fields may be assigned to only once. (Hard to implement in
 		//       JustIce's execution model). This may only happen in <clinit>, see Pass 3a.
 
 	    } catch (ClassNotFoundException e) {
 		// FIXME: maybe not the best way to handle this
 		throw new AssertionViolatedException("Missing class: " + e.toString());
 	    }
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitRET(RET o){
 		if (! (locals().get(o.getIndex()) instanceof ReturnaddressType)){
 			constraintViolated(o, "Expecting a ReturnaddressType in local variable "+o.getIndex()+".");
 		}
 		if (locals().get(o.getIndex()) == ReturnaddressType.NO_TARGET){
 			throw new AssertionViolatedException("Oops: RET expecting a target!");
 		}
 		// Other constraints such as non-allowed overlapping subroutines are enforced
 		// while building the Subroutines data structure.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitRETURN(RETURN o){
 		if (mg.getName().equals(Constants.CONSTRUCTOR_NAME)){// If we leave an <init> method
 			if ((Frame._this != null) && (!(mg.getClassName().equals(Type.OBJECT.getClassName()))) ) {
 				constraintViolated(o, "Leaving a constructor that itself did not call a constructor.");
 			}
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitSALOAD(SALOAD o){
 		indexOfInt(o, stack().peek());
 		if (stack().peek(1) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(1) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-top must be of type short[] but is '"+stack().peek(1)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(1))).getBasicType();
 		if (t != Type.SHORT){
 			constraintViolated(o, "Stack next-to-top must be of type short[] but is '"+stack().peek(1)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitSASTORE(SASTORE o){
 		if (stack().peek() != Type.INT){
 			constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
 		}
 		indexOfInt(o, stack().peek(1));
 		if (stack().peek(2) == Type.NULL){
 			return;
 		} 
 		if (! (stack().peek(2) instanceof ArrayType)){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type short[] but is '"+stack().peek(2)+"'.");
 		}
 		Type t = ((ArrayType) (stack().peek(2))).getBasicType();
 		if (t != Type.SHORT){
 			constraintViolated(o, "Stack next-to-next-to-top must be of type short[] but is '"+stack().peek(2)+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitSIPUSH(SIPUSH o){
 		// nothing to do here. Generic visitXXX() methods did the trick before.
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitSWAP(SWAP o){
 		if (stack().peek().getSize() != 1){
 			constraintViolated(o, "The value at the stack top is not of size '1', but of size '"+stack().peek().getSize()+"'.");
 		}
 		if (stack().peek(1).getSize() != 1){
 			constraintViolated(o, "The value at the stack next-to-top is not of size '1', but of size '"+stack().peek(1).getSize()+"'.");
 		}
 	}
 
 	/***
 	 * Ensures the specific preconditions of the said instruction.
 	 */
 	public void visitTABLESWITCH(TABLESWITCH o){
 		indexOfInt(o, stack().peek());
 		// See Pass 3a.
 	}
 
 }