org.aspectj/bcel-builder/verifier-src/org/aspectj/apache/bcel/verifier/statics/Pass3aVerifier.java

package org.aspectj.apache.bcel.verifier.statics;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (https://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <https://www.apache.org/>.
 */

import org.aspectj.apache.bcel.Constants;
import org.aspectj.apache.bcel.Repository;
import org.aspectj.apache.bcel.classfile.Attribute;
import org.aspectj.apache.bcel.classfile.Code;
import org.aspectj.apache.bcel.classfile.CodeException;
import org.aspectj.apache.bcel.classfile.Constant;
import org.aspectj.apache.bcel.classfile.ConstantClass;
import org.aspectj.apache.bcel.classfile.ConstantDouble;
import org.aspectj.apache.bcel.classfile.ConstantFieldref;
import org.aspectj.apache.bcel.classfile.ConstantFloat;
import org.aspectj.apache.bcel.classfile.ConstantInteger;
import org.aspectj.apache.bcel.classfile.ConstantInterfaceMethodref;
import org.aspectj.apache.bcel.classfile.ConstantLong;
import org.aspectj.apache.bcel.classfile.ConstantMethodref;
import org.aspectj.apache.bcel.classfile.ConstantNameAndType;
import org.aspectj.apache.bcel.classfile.ConstantPool;
import org.aspectj.apache.bcel.classfile.ConstantString;
import org.aspectj.apache.bcel.classfile.ConstantUtf8;
import org.aspectj.apache.bcel.classfile.Field;
import org.aspectj.apache.bcel.classfile.JavaClass;
import org.aspectj.apache.bcel.classfile.LineNumber;
import org.aspectj.apache.bcel.classfile.LineNumberTable;
import org.aspectj.apache.bcel.classfile.LocalVariable;
import org.aspectj.apache.bcel.classfile.LocalVariableTable;
import org.aspectj.apache.bcel.classfile.Method;
import org.aspectj.apache.bcel.generic.ArrayType;
import org.aspectj.apache.bcel.generic.FieldInstruction;
import org.aspectj.apache.bcel.generic.IINC;
import org.aspectj.apache.bcel.generic.INVOKEINTERFACE;
import org.aspectj.apache.bcel.generic.Instruction;
import org.aspectj.apache.bcel.generic.InstructionBranch;
import org.aspectj.apache.bcel.generic.InstructionByte;
import org.aspectj.apache.bcel.generic.InstructionHandle;
import org.aspectj.apache.bcel.generic.InstructionList;
import org.aspectj.apache.bcel.generic.InvokeInstruction;
import org.aspectj.apache.bcel.generic.LOOKUPSWITCH;
import org.aspectj.apache.bcel.generic.MULTIANEWARRAY;
import org.aspectj.apache.bcel.generic.ObjectType;
import org.aspectj.apache.bcel.generic.RET;
import org.aspectj.apache.bcel.generic.TABLESWITCH;
import org.aspectj.apache.bcel.generic.Type;
import org.aspectj.apache.bcel.verifier.InstructionWalker;
import org.aspectj.apache.bcel.verifier.PassVerifier;
import org.aspectj.apache.bcel.verifier.VerificationResult;
import org.aspectj.apache.bcel.verifier.Verifier;
import org.aspectj.apache.bcel.verifier.VerifierFactory;
import org.aspectj.apache.bcel.verifier.exc.AssertionViolatedException;
import org.aspectj.apache.bcel.verifier.exc.ClassConstraintException;
import org.aspectj.apache.bcel.verifier.exc.InvalidMethodException;
import org.aspectj.apache.bcel.verifier.exc.StaticCodeConstraintException;
import org.aspectj.apache.bcel.verifier.exc.StaticCodeInstructionConstraintException;
import org.aspectj.apache.bcel.verifier.exc.StaticCodeInstructionOperandConstraintException;

/**
 * This PassVerifier verifies a class file according to pass 3, static part as described in The Java Virtual Machine Specification,
 * 2nd edition. More detailed information is to be found at the do_verify() method's documentation.
 *
 * @version $Id: Pass3aVerifier.java,v 1.5 2009/09/10 15:35:06 aclement Exp $
 * @author <A HREF="https://www.inf.fu-berlin.de/~ehaase"/>Enver Haase</A>
 * @see #do_verify()
 */
public final class Pass3aVerifier extends PassVerifier {

	/** The Verifier that created this. */
	private final Verifier myOwner;

	/**
	 * The method number to verify. This is the index in the array returned by JavaClass.getMethods().
	 */
	private final int method_no;

	/**
	 * The one and only InstructionList object used by an instance of this class. It's here for performance reasons by do_verify()
	 * and its callees.
	 */
	InstructionList instructionList;
	/**
	 * The one and only Code object used by an instance of this class. It's here for performance reasons by do_verify() and its
	 * callees.
	 */
	Code code;

	/** Should only be instantiated by a Verifier. */
	public Pass3aVerifier(Verifier owner, int method_no) {
		myOwner = owner;
		this.method_no = method_no;
	}

	/**
	 * Pass 3a is the verification of static constraints of JVM code (such as legal targets of branch instructions). This is the
	 * part of pass 3 where you do not need data flow analysis. JustIce also delays the checks for a correct exception table of a
	 * Code attribute and correct line number entries in a LineNumberTable attribute of a Code attribute (which conceptually belong
	 * to pass 2) to this pass. Also, most of the check for valid local variable entries in a LocalVariableTable attribute of a Code
	 * attribute is delayed until this pass. All these checks need access to the code array of the Code attribute.
	 *
	 * @throws InvalidMethodException if the method to verify does not exist.
	 */
	@Override
	public VerificationResult do_verify() {
		if (myOwner.doPass2().equals(VerificationResult.VR_OK)) {
			// Okay, class file was loaded correctly by Pass 1
			// and satisfies static constraints of Pass 2.
			JavaClass jc = Repository.lookupClass(myOwner.getClassName());
			Method[] methods = jc.getMethods();
			if (method_no >= methods.length) {
				throw new InvalidMethodException("METHOD DOES NOT EXIST!");
			}
			Method method = methods[method_no];
			code = method.getCode();

			// No Code? Nothing to verify!
			if (method.isAbstract() || method.isNative()) { // IF mg HAS NO CODE (static constraint of Pass 2)
				return VerificationResult.VR_OK;
			}

			// TODO:
			// We want a very sophisticated code examination here with good explanations
			// on where to look for an illegal instruction or such.
			// Only after that we should try to build an InstructionList and throw an
			// AssertionViolatedException if after our examination InstructionList building
			// still fails.
			// That examination should be implemented in a byte-oriented way, i.e. look for
			// an instruction, make sure its validity, count its length, find the next
			// instruction and so on.
			try {
				instructionList = new InstructionList(method.getCode().getCode());
			} catch (RuntimeException re) {
				return new VerificationResult(VerificationResult.VERIFIED_REJECTED,
						"Bad bytecode in the code array of the Code attribute of method '" + method + "'.");
			}

			instructionList.setPositions(true);

			// Start verification.
			VerificationResult vr = VerificationResult.VR_OK; // default
			try {
				delayedPass2Checks();
			} catch (ClassConstraintException cce) {
				vr = new VerificationResult(VerificationResult.VERIFIED_REJECTED, cce.getMessage());
				return vr;
			}
			try {
				pass3StaticInstructionChecks();
				pass3StaticInstructionOperandsChecks();
			} catch (StaticCodeConstraintException scce) {
				vr = new VerificationResult(VerificationResult.VERIFIED_REJECTED, scce.getMessage());
			}
			return vr;
		} else { // did not pass Pass 2.
			return VerificationResult.VR_NOTYET;
		}
	}

	/**
	 * These are the checks that could be done in pass 2 but are delayed to pass 3 for performance reasons. Also, these checks need
	 * access to the code array of the Code attribute of a Method so it's okay to perform them here. Also see the description of the
	 * do_verify() method.
	 *
	 * @throws ClassConstraintException if the verification fails.
	 * @see #do_verify()
	 */
	private void delayedPass2Checks() {

		int[] instructionPositions = instructionList.getInstructionPositions();
		int codeLength = code.getCode().length;

		// ///////////////////
		// LineNumberTable //
		// ///////////////////
		LineNumberTable lnt = code.getLineNumberTable();
		if (lnt != null) {
			LineNumber[] lineNumbers = lnt.getLineNumberTable();
			IntList offsets = new IntList();
			lineNumber_loop: for (int i = 0; i < lineNumbers.length; i++) { // may appear in any order.
				for (int j = 0; j < instructionPositions.length; j++) {
					// TODO: Make this a binary search! The instructionPositions array is naturally ordered!
					int offset = lineNumbers[i].getStartPC();
					if (instructionPositions[j] == offset) {
						if (offsets.contains(offset)) {
							addMessage("LineNumberTable attribute '"
									+ code.getLineNumberTable()
									+ "' refers to the same code offset ('"
									+ offset
									+ "') more than once which is violating the semantics [but is sometimes produced by IBM's 'jikes' compiler].");
						} else {
							offsets.add(offset);
						}
						continue lineNumber_loop;
					}
				}
				throw new ClassConstraintException("Code attribute '" + code + "' has a LineNumberTable attribute '"
						+ code.getLineNumberTable() + "' referring to a code offset ('" + lineNumbers[i].getStartPC()
						+ "') that does not exist.");
			}
		}

		// /////////////////////////
		// LocalVariableTable(s) //
		// /////////////////////////
		/*
		 * We cannot use code.getLocalVariableTable() because there could be more than only one. This is a bug in BCEL.
		 */
		Attribute[] atts = code.getAttributes();
		for (int a = 0; a < atts.length; a++) {
			if (atts[a] instanceof LocalVariableTable) {
				LocalVariableTable lvt = (LocalVariableTable) atts[a];
				if (lvt != null) {
					LocalVariable[] localVariables = lvt.getLocalVariableTable();
					for (int i = 0; i < localVariables.length; i++) {
						int startpc = localVariables[i].getStartPC();
						int length = localVariables[i].getLength();

						if (!contains(instructionPositions, startpc)) {
							throw new ClassConstraintException("Code attribute '" + code + "' has a LocalVariableTable attribute '"
									+ code.getLocalVariableTable() + "' referring to a code offset ('" + startpc
									+ "') that does not exist.");
						}
						if (!contains(instructionPositions, startpc + length) && startpc + length != codeLength) {
							throw new ClassConstraintException("Code attribute '" + code + "' has a LocalVariableTable attribute '"
									+ code.getLocalVariableTable() + "' referring to a code offset start_pc+length ('"
									+ (startpc + length) + "') that does not exist.");
						}
					}
				}
			}
		}

		// //////////////////
		// ExceptionTable //
		// //////////////////
		// In BCEL's "classfile" API, the startPC/endPC-notation is
		// inclusive/exclusive as in the Java Virtual Machine Specification.
		// WARNING: This is not true for BCEL's "generic" API.
		CodeException[] exceptionTable = code.getExceptionTable();
		for (int i = 0; i < exceptionTable.length; i++) {
			int startpc = exceptionTable[i].getStartPC();
			int endpc = exceptionTable[i].getEndPC();
			int handlerpc = exceptionTable[i].getHandlerPC();
			if (startpc >= endpc) {
				throw new ClassConstraintException("Code attribute '" + code + "' has an exception_table entry '"
						+ exceptionTable[i] + "' that has its start_pc ('" + startpc + "') not smaller than its end_pc ('" + endpc
						+ "').");
			}
			if (!contains(instructionPositions, startpc)) {
				throw new ClassConstraintException("Code attribute '" + code + "' has an exception_table entry '"
						+ exceptionTable[i] + "' that has a non-existant bytecode offset as its start_pc ('" + startpc + "').");
			}
			if (!contains(instructionPositions, endpc) && endpc != codeLength) {
				throw new ClassConstraintException("Code attribute '" + code + "' has an exception_table entry '"
						+ exceptionTable[i] + "' that has a non-existant bytecode offset as its end_pc ('" + startpc
						+ "') [that is also not equal to code_length ('" + codeLength + "')].");
			}
			if (!contains(instructionPositions, handlerpc)) {
				throw new ClassConstraintException("Code attribute '" + code + "' has an exception_table entry '"
						+ exceptionTable[i] + "' that has a non-existant bytecode offset as its handler_pc ('" + handlerpc + "').");
			}
		}
	}

	/**
	 * These are the checks if constraints are satisfied which are described in the Java Virtual Machine Specification, Second
	 * Edition as Static Constraints on the instructions of Java Virtual Machine Code (chapter 4.8.1).
	 *
	 * @throws StaticCodeConstraintException if the verification fails.
	 */
	private void pass3StaticInstructionChecks() {

		// Code array must not be empty:
		// Enforced in pass 2 (also stated in the static constraints of the Code
		// array in vmspec2), together with pass 1 (reading code_length bytes and
		// interpreting them as code[]). So this must not be checked again here.

		if (!(code.getCode().length < 65536)) {// contradicts vmspec2 page 152 ("Limitations"), but is on page 134.
			throw new StaticCodeInstructionConstraintException("Code array in code attribute '" + code
					+ "' too big: must be smaller than 65536 bytes.");
		}

		// First opcode at offset 0: okay, that's clear. Nothing to do.

		// Only instances of the instructions documented in Section 6.4 may appear in
		// the code array.

		// For BCEL's sake, we cannot handle WIDE stuff, but hopefully BCEL does its job right :)

		// The last byte of the last instruction in the code array must be the byte at index
		// code_length-1 : See the do_verify() comments. We actually don't iterate through the
		// byte array, but use an InstructionList so we cannot check for this. But BCEL does
		// things right, so it's implicitly okay.

		// TODO: Check how BCEL handles (and will handle) instructions like IMPDEP1, IMPDEP2,
		// BREAKPOINT... that BCEL knows about but which are illegal anyway.
		// We currently go the safe way here.
		InstructionHandle ih = instructionList.getStart();
		while (ih != null) {
			Instruction i = ih.getInstruction();
			if (i.getOpcode() == Constants.IMPDEP1) {
				throw new StaticCodeInstructionConstraintException(
						"IMPDEP1 must not be in the code, it is an illegal instruction for _internal_ JVM use!");
			}
			if (i.getOpcode() == Constants.IMPDEP2) {
				throw new StaticCodeInstructionConstraintException(
						"IMPDEP2 must not be in the code, it is an illegal instruction for _internal_ JVM use!");
			}
			if (i.getOpcode() == Constants.BREAKPOINT) {
				throw new StaticCodeInstructionConstraintException(
						"BREAKPOINT must not be in the code, it is an illegal instruction for _internal_ JVM use!");
			}
			ih = ih.getNext();
		}

		// The original verifier seems to do this check here, too.
		// An unreachable last instruction may also not fall through the
		// end of the code, which is stupid -- but with the original
		// verifier's subroutine semantics one cannot predict reachability.
		Instruction last = instructionList.getEnd().getInstruction();
		if (!(last.isReturnInstruction() || last instanceof RET || last.getOpcode() == Constants.GOTO
				|| last.getOpcode() == Constants.GOTO_W || last.getOpcode() == Constants.ATHROW)) {
			throw new StaticCodeInstructionConstraintException(
					"Execution must not fall off the bottom of the code array. This constraint is enforced statically as some existing verifiers do - so it may be a false alarm if the last instruction is not reachable.");
		}
	}

	/**
	 * These are the checks for the satisfaction of constraints which are described in the Java Virtual Machine Specification,
	 * Second Edition as Static Constraints on the operands of instructions of Java Virtual Machine Code (chapter 4.8.1). BCEL
	 * parses the code array to create an InstructionList and therefore has to check some of these constraints. Additional checks
	 * are also implemented here.
	 *
	 * @throws StaticCodeConstraintException if the verification fails.
	 */
	private void pass3StaticInstructionOperandsChecks() {
		// When building up the InstructionList, BCEL has already done all those checks
		// mentioned in The Java Virtual Machine Specification, Second Edition, as
		// "static constraints on the operands of instructions in the code array".
		// TODO: see the do_verify() comments. Maybe we should really work on the
		// byte array first to give more comprehensive messages.
		// TODO: Review Exception API, possibly build in some "offending instruction" thing
		// when we're ready to insulate the offending instruction by doing the
		// above thing.

		// TODO: Implement as much as possible here. BCEL does _not_ check everything.

		ConstantPool cpg = new ConstantPool(Repository.lookupClass(myOwner.getClassName()).getConstantPool().getConstantPool());
		InstOperandConstraintVisitor v = new InstOperandConstraintVisitor(cpg);

		// Checks for the things BCEL does _not_ handle itself.
		InstructionHandle ih = instructionList.getStart();
		while (ih != null) {
			Instruction i = ih.getInstruction();

			// An "own" constraint, due to JustIce's new definition of what "subroutine" means.
			if (i.isJsrInstruction()) {
				InstructionHandle target = ((InstructionBranch) i).getTarget();
				if (target == instructionList.getStart()) {
					throw new StaticCodeInstructionOperandConstraintException(
							"Due to JustIce's clear definition of subroutines, no JSR or JSR_W may have a top-level instruction (such as the very first instruction, which is targeted by instruction '"
									+ ih + "' as its target.");
				}
				if (!target.getInstruction().isASTORE()) {
					throw new StaticCodeInstructionOperandConstraintException(
							"Due to JustIce's clear definition of subroutines, no JSR or JSR_W may target anything else than an ASTORE instruction. Instruction '"
									+ ih + "' targets '" + target + "'.");
				}
			}

			// vmspec2, page 134-137
			InstructionWalker.accept(ih.getInstruction(), v);

			ih = ih.getNext();
		}

	}

	/** A small utility method returning if a given int i is in the given int[] ints. */
	private static boolean contains(int[] ints, int i) {
		for (int j = 0; j < ints.length; j++) {
			if (ints[j] == i) {
				return true;
			}
		}
		return false;
	}

	/** Returns the method number as supplied when instantiating. */
	public int getMethodNo() {
		return method_no;
	}

	/**
	 * This visitor class does the actual checking for the instruction operand's constraints.
	 */
	private class InstOperandConstraintVisitor extends org.aspectj.apache.bcel.verifier.EmptyInstVisitor {
		/** The ConstantPoolGen instance this Visitor operates on. */
		private final ConstantPool cpg;

		/** The only Constructor. */
		InstOperandConstraintVisitor(ConstantPool cpg) {
			this.cpg = cpg;
		}

		/**
		 * Utility method to return the max_locals value of the method verified by the surrounding Pass3aVerifier instance.
		 */
		private int max_locals() {
			return Repository.lookupClass(myOwner.getClassName()).getMethods()[method_no].getCode().getMaxLocals();
		}

		/**
		 * A utility method to always raise an exeption.
		 */
		private void constraintViolated(Instruction i, String message) {
			throw new StaticCodeInstructionOperandConstraintException("Instruction " + i + " constraint violated: " + message);
		}

		/**
		 * A utility method to raise an exception if the index is not a valid constant pool index.
		 */
		private void indexValid(Instruction i, int idx) {
			if (idx < 0 || idx >= cpg.getSize()) {
				constraintViolated(i, "Illegal constant pool index '" + idx + "'.");
			}
		}

		// /////////////////////////////////////////////////////////
		// The Java Virtual Machine Specification, pages 134-137 //
		// /////////////////////////////////////////////////////////
		/**
		 * Assures the generic preconditions of a LoadClass instance. The referenced class is loaded and pass2-verified.
		 */
		@Override
		public void visitLoadClass(Instruction o) {
			ObjectType t = o.getLoadClassType(cpg);
			if (t != null) {// null means "no class is loaded"
				Verifier v = VerifierFactory.getVerifier(t.getClassName());
				VerificationResult vr = v.doPass1();
				if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
					constraintViolated(o, "Class '" + o.getLoadClassType(cpg).getClassName()
							+ "' is referenced, but cannot be loaded: '" + vr + "'.");
				}
			}
		}

		// The target of each jump and branch instruction [...] must be the opcode [...]
		// BCEL _DOES_ handle this.

		// tableswitch: BCEL will do it, supposedly.

		// lookupswitch: BCEL will do it, supposedly.

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		// LDC and LDC_W (LDC_W is a subclass of LDC in BCEL's model)
		@Override
		public void visitLDC(Instruction o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantInteger || c instanceof ConstantFloat || c instanceof ConstantString)) {
				constraintViolated(o,
						"Operand of LDC or LDC_W must be one of CONSTANT_Integer, CONSTANT_Float or CONSTANT_String, but is '" + c
								+ "'.");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		// LDC2_W
		@Override
		public void visitLDC2_W(Instruction o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantLong || c instanceof ConstantDouble)) {
				constraintViolated(o, "Operand of LDC2_W must be CONSTANT_Long or CONSTANT_Double, but is '" + c + "'.");
			}
			try {
				indexValid(o, o.getIndex() + 1);
			} catch (StaticCodeInstructionOperandConstraintException e) {
				throw new AssertionViolatedException("OOPS: Does not BCEL handle that? LDC2_W operand has a problem.");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		// getfield, putfield, getstatic, putstatic
		public void visitFieldInstruction(FieldInstruction o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantFieldref)) {
				constraintViolated(o, "Indexing a constant that's not a CONSTANT_Fieldref but a '" + c + "'.");
			}

			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)) {
					f = fields[i];
					break;
				}
			}
			if (f == null) {
				/* TODO: also look up if the field is inherited! */
				constraintViolated(o, "Referenced field '" + field_name + "' does not exist in class '" + jc.getClassName() + "'.");
			} else {
				/*
				 * TODO: Check if assignment compatibility is sufficient. What does Sun do?
				 */
				Type f_type = Type.getType(f.getSignature());
				Type o_type = o.getType(cpg);

				/*
				 * TODO: Is there a way to make BCEL tell us if a field has a void method's signature, i.e. "()I" instead of "I"?
				 */

				if (!f_type.equals(o_type)) {
					constraintViolated(o, "Referenced field '" + field_name + "' has type '" + f_type + "' instead of '" + o_type
							+ "' as expected.");
				}
				/* TODO: Check for access modifiers here. */
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		@Override
		public void visitInvokeInstruction(InvokeInstruction o) {
			indexValid(o, o.getIndex());
			if (o.getOpcode() == Constants.INVOKEVIRTUAL || o.getOpcode() == Constants.INVOKESPECIAL
					|| o.getOpcode() == Constants.INVOKESTATIC) {
				Constant c = cpg.getConstant(o.getIndex());
				if (!(c instanceof ConstantMethodref)) {
					constraintViolated(o, "Indexing a constant that's not a CONSTANT_Methodref but a '" + c + "'.");
				} else {
					// Constants are okay due to pass2.
					ConstantNameAndType cnat = (ConstantNameAndType) cpg.getConstant(((ConstantMethodref) c).getNameAndTypeIndex());
					ConstantUtf8 cutf8 = (ConstantUtf8) cpg.getConstant(cnat.getNameIndex());
					if (cutf8.getValue().equals(Constants.CONSTRUCTOR_NAME) && !(o.getOpcode() == Constants.INVOKESPECIAL)) {
						constraintViolated(o, "Only INVOKESPECIAL is allowed to invoke instance initialization methods.");
					}
					if (!cutf8.getValue().equals(Constants.CONSTRUCTOR_NAME) && cutf8.getValue().startsWith("<")) {
						constraintViolated(
								o,
								"No method with a name beginning with '<' other than the instance initialization methods may be called by the method invocation instructions.");
					}
				}
			} else { // if (o instanceof INVOKEINTERFACE){
				Constant c = cpg.getConstant(o.getIndex());
				if (!(c instanceof ConstantInterfaceMethodref)) {
					constraintViolated(o, "Indexing a constant that's not a CONSTANT_InterfaceMethodref but a '" + c + "'.");
				}
				// TODO: From time to time check if BCEL allows to detect if the
				// 'count' operand is consistent with the information in the
				// CONSTANT_InterfaceMethodref and if the last operand is zero.
				// By now, BCEL hides those two operands because they're superfluous.

				// Invoked method must not be <init> or <clinit>
				ConstantNameAndType cnat = (ConstantNameAndType) cpg.getConstant(((ConstantInterfaceMethodref) c)
						.getNameAndTypeIndex());
				String name = ((ConstantUtf8) cpg.getConstant(cnat.getNameIndex())).getValue();
				if (name.equals(Constants.CONSTRUCTOR_NAME)) {
					constraintViolated(o, "Method to invoke must not be '" + Constants.CONSTRUCTOR_NAME + "'.");
				}
				if (name.equals(Constants.STATIC_INITIALIZER_NAME)) {
					constraintViolated(o, "Method to invoke must not be '" + Constants.STATIC_INITIALIZER_NAME + "'.");
				}
			}

			// The LoadClassType is the method-declaring class, so we have to check the other types.

			Type t = o.getReturnType(cpg);
			if (t instanceof ArrayType) {
				t = ((ArrayType) t).getBasicType();
			}
			if (t instanceof ObjectType) {
				Verifier v = VerifierFactory.getVerifier(((ObjectType) t).getClassName());
				VerificationResult vr = v.doPass2();
				if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
					constraintViolated(o, "Return type class/interface could not be verified successfully: '" + vr.getMessage()
							+ "'.");
				}
			}

			Type[] ts = o.getArgumentTypes(cpg);
			for (int i = 0; i < ts.length; i++) {
				t = ts[i];
				if (t instanceof ArrayType) {
					t = ((ArrayType) t).getBasicType();
				}
				if (t instanceof ObjectType) {
					Verifier v = VerifierFactory.getVerifier(((ObjectType) t).getClassName());
					VerificationResult vr = v.doPass2();
					if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
						constraintViolated(o, "Argument type class/interface could not be verified successfully: '"
								+ vr.getMessage() + "'.");
					}
				}
			}

		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		@Override
		public void visitINSTANCEOF(Instruction o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantClass)) {
				constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + c + "'.");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		@Override
		public void visitCHECKCAST(Instruction o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantClass)) {
				constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + c + "'.");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		@Override
		public void visitNEW(Instruction o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantClass)) {
				constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + c + "'.");
			} else {
				ConstantUtf8 cutf8 = (ConstantUtf8) cpg.getConstant(((ConstantClass) c).getNameIndex());
				Type t = Type.getType("L" + cutf8.getValue() + ";");
				if (t instanceof ArrayType) {
					constraintViolated(o, "NEW must not be used to create an array.");
				}
			}

		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitMULTIANEWARRAY(MULTIANEWARRAY o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantClass)) {
				constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + c + "'.");
			}
			int dimensions2create = o.getDimensions();
			if (dimensions2create < 1) {
				constraintViolated(o, "Number of dimensions to create must be greater than zero.");
			}
			Type t = o.getType(cpg);
			if (t instanceof ArrayType) {
				int dimensions = ((ArrayType) t).getDimensions();
				if (dimensions < dimensions2create) {
					constraintViolated(o,
							"Not allowed to create array with more dimensions ('+dimensions2create+') than the one referenced by the CONSTANT_Class '"
									+ t + "'.");
				}
			} else {
				constraintViolated(
						o,
						"Expecting a CONSTANT_Class referencing an array type. [Constraint not found in The Java Virtual Machine Specification, Second Edition, 4.8.1]");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitANEWARRAY(Instruction o) {
			indexValid(o, o.getIndex());
			Constant c = cpg.getConstant(o.getIndex());
			if (!(c instanceof ConstantClass)) {
				constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + c + "'.");
			}
			Type t = o.getType(cpg);
			if (t instanceof ArrayType) {
				int dimensions = ((ArrayType) t).getDimensions();
				if (dimensions >= 255) {
					constraintViolated(o, "Not allowed to create an array with more than 255 dimensions.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitNEWARRAY(Instruction o) {
			byte t = ((InstructionByte) o).getTypecode();
			if (!(t == Constants.T_BOOLEAN || t == Constants.T_CHAR || t == Constants.T_FLOAT || t == Constants.T_DOUBLE
					|| t == Constants.T_BYTE || t == Constants.T_SHORT || t == Constants.T_INT || t == Constants.T_LONG)) {
				constraintViolated(o, "Illegal type code '+t+' for 'atype' operand.");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitILOAD(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitFLOAD(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitALOAD(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitISTORE(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitFSTORE(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitASTORE(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitIINC(IINC o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitRET(RET o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(o, "Index '" + idx + "' must be non-negative.");
			} else {
				int maxminus1 = max_locals() - 1;
				if (idx > maxminus1) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitLLOAD(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(
						o,
						"Index '"
								+ idx
								+ "' must be non-negative. [Constraint by JustIce as an analogon to the single-slot xLOAD/xSTORE instructions; may not happen anyway.]");
			} else {
				int maxminus2 = max_locals() - 2;
				if (idx > maxminus2) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-2 '" + maxminus2 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitDLOAD(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(
						o,
						"Index '"
								+ idx
								+ "' must be non-negative. [Constraint by JustIce as an analogon to the single-slot xLOAD/xSTORE instructions; may not happen anyway.]");
			} else {
				int maxminus2 = max_locals() - 2;
				if (idx > maxminus2) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-2 '" + maxminus2 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitLSTORE(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(
						o,
						"Index '"
								+ idx
								+ "' must be non-negative. [Constraint by JustIce as an analogon to the single-slot xLOAD/xSTORE instructions; may not happen anyway.]");
			} else {
				int maxminus2 = max_locals() - 2;
				if (idx > maxminus2) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-2 '" + maxminus2 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitDSTORE(Instruction o) {
			int idx = o.getIndex();
			if (idx < 0) {
				constraintViolated(
						o,
						"Index '"
								+ idx
								+ "' must be non-negative. [Constraint by JustIce as an analogon to the single-slot xLOAD/xSTORE instructions; may not happen anyway.]");
			} else {
				int maxminus2 = max_locals() - 2;
				if (idx > maxminus2) {
					constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-2 '" + maxminus2 + "'.");
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitLOOKUPSWITCH(LOOKUPSWITCH o) {
			int[] matchs = o.getMatchs();
			int max = Integer.MIN_VALUE;
			for (int i = 0; i < matchs.length; i++) {
				if (matchs[i] == max && i != 0) {
					constraintViolated(o, "Match '" + matchs[i] + "' occurs more than once.");
				}
				if (matchs[i] < max) {
					constraintViolated(o, "Lookup table must be sorted but isn't.");
				} else {
					max = matchs[i];
				}
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitTABLESWITCH(TABLESWITCH o) {
			// "high" must be >= "low". We cannot check this, as BCEL hides
			// it from us.
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitPUTSTATIC(FieldInstruction o) {
			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)) {
					f = fields[i];
					break;
				}
			}
			if (f == null) {
				throw new AssertionViolatedException("Field not found?!?");
			}

			if (f.isFinal()) {
				if (!myOwner.getClassName().equals(o.getClassType(cpg).getClassName())) {
					constraintViolated(o, "Referenced field '" + f
							+ "' is final and must therefore be declared in the current class '" + myOwner.getClassName()
							+ "' which is not the case: it is declared in '" + o.getClassType(cpg).getClassName() + "'.");
				}
			}

			if (!f.isStatic()) {
				constraintViolated(o, "Referenced field '" + f + "' is not static which it should be.");
			}

			String meth_name = Repository.lookupClass(myOwner.getClassName()).getMethods()[method_no].getName();

			// If it's an interface, it can be set only in <clinit>.
			if (!jc.isClass() && !meth_name.equals(Constants.STATIC_INITIALIZER_NAME)) {
				constraintViolated(o, "Interface field '" + f + "' must be set in a '" + Constants.STATIC_INITIALIZER_NAME
						+ "' method.");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitGETSTATIC(FieldInstruction o) {
			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)) {
					f = fields[i];
					break;
				}
			}
			if (f == null) {
				throw new AssertionViolatedException("Field not found?!?");
			}

			if (!f.isStatic()) {
				constraintViolated(o, "Referenced field '" + f + "' is not static which it should be.");
			}
		}

		/* Checks if the constraints of operands of the said instruction(s) are satisfied. */
		// public void visitPUTFIELD(PUTFIELD o){
		// for performance reasons done in Pass 3b
		// }
		/* Checks if the constraints of operands of the said instruction(s) are satisfied. */
		// public void visitGETFIELD(GETFIELD o){
		// for performance reasons done in Pass 3b
		// }
		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitINVOKEINTERFACE(INVOKEINTERFACE o) {
			// INVOKEINTERFACE is a LoadClass; the Class where the referenced method is declared in,
			// is therefore resolved/verified.
			// INVOKEINTERFACE is an InvokeInstruction, the argument and return types are resolved/verified,
			// too. So are the allowed method names.
			String classname = o.getClassName(cpg);
			JavaClass jc = Repository.lookupClass(classname);
			Method[] ms = jc.getMethods();
			Method m = null;
			for (int i = 0; i < ms.length; i++) {
				if (ms[i].getName().equals(o.getMethodName(cpg))
						&& Type.getReturnType(ms[i].getSignature()).equals(o.getReturnType(cpg))
						&& objarrayequals(Type.getArgumentTypes(ms[i].getSignature()), o.getArgumentTypes(cpg))) {
					m = ms[i];
					break;
				}
			}
			if (m == null) {
				constraintViolated(
						o,
						"Referenced method '"
								+ o.getMethodName(cpg)
								+ "' with expected signature not found in class '"
								+ jc.getClassName()
								+ "'. The native verfier does allow the method to be declared in some superinterface, which the Java Virtual Machine Specification, Second Edition does not.");
			}
			if (jc.isClass()) {
				constraintViolated(o, "Referenced class '" + jc.getClassName() + "' is a class, but not an interface as expected.");
			}
		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitINVOKESPECIAL(InvokeInstruction o) {
			// INVOKESPECIAL is a LoadClass; the Class where the referenced method is declared in,
			// is therefore resolved/verified.
			// INVOKESPECIAL is an InvokeInstruction, the argument and return types are resolved/verified,
			// too. So are the allowed method names.
			String classname = o.getClassName(cpg);
			JavaClass jc = Repository.lookupClass(classname);
			Method[] ms = jc.getMethods();
			Method m = null;
			for (int i = 0; i < ms.length; i++) {
				if (ms[i].getName().equals(o.getMethodName(cpg))
						&& Type.getReturnType(ms[i].getSignature()).equals(o.getReturnType(cpg))
						&& objarrayequals(Type.getArgumentTypes(ms[i].getSignature()), o.getArgumentTypes(cpg))) {
					m = ms[i];
					break;
				}
			}
			if (m == null) {
				constraintViolated(
						o,
						"Referenced method '"
								+ o.getMethodName(cpg)
								+ "' with expected signature not found in class '"
								+ jc.getClassName()
								+ "'. The native verfier does allow the method to be declared in some superclass or implemented interface, which the Java Virtual Machine Specification, Second Edition does not.");
			}

			JavaClass current = Repository.lookupClass(myOwner.getClassName());
			if (current.isSuper()) {

				if (Repository.instanceOf(current, jc) && !current.equals(jc)) {

					if (!o.getMethodName(cpg).equals(Constants.CONSTRUCTOR_NAME)) {
						// Special lookup procedure for ACC_SUPER classes.

						int supidx = -1;

						Method meth = null;
						while (supidx != 0) {
							supidx = current.getSuperclassNameIndex();
							current = Repository.lookupClass(current.getSuperclassName());

							Method[] meths = current.getMethods();
							for (int i = 0; i < meths.length; i++) {
								if (meths[i].getName().equals(o.getMethodName(cpg))
										&& Type.getReturnType(meths[i].getSignature()).equals(o.getReturnType(cpg))
										&& objarrayequals(Type.getArgumentTypes(meths[i].getSignature()), o.getArgumentTypes(cpg))) {
									meth = meths[i];
									break;
								}
							}
							if (meth != null) {
								break;
							}
						}
						if (meth == null) {
							constraintViolated(o, "ACC_SUPER special lookup procedure not successful: method '"
									+ o.getMethodName(cpg) + "' with proper signature not declared in superclass hierarchy.");
						}
					}
				}
			}

		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitINVOKESTATIC(InvokeInstruction o) {
			// INVOKESTATIC is a LoadClass; the Class where the referenced method is declared in,
			// is therefore resolved/verified.
			// INVOKESTATIC is an InvokeInstruction, the argument and return types are resolved/verified,
			// too. So are the allowed method names.
			String classname = o.getClassName(cpg);
			JavaClass jc = Repository.lookupClass(classname);
			Method[] ms = jc.getMethods();
			Method m = null;
			for (int i = 0; i < ms.length; i++) {
				if (ms[i].getName().equals(o.getMethodName(cpg))
						&& Type.getReturnType(ms[i].getSignature()).equals(o.getReturnType(cpg))
						&& objarrayequals(Type.getArgumentTypes(ms[i].getSignature()), o.getArgumentTypes(cpg))) {
					m = ms[i];
					break;
				}
			}
			if (m == null) {
				constraintViolated(
						o,
						"Referenced method '"
								+ o.getMethodName(cpg)
								+ "' with expected signature not found in class '"
								+ jc.getClassName()
								+ "'. The native verifier possibly allows the method to be declared in some superclass or implemented interface, which the Java Virtual Machine Specification, Second Edition does not.");
			}

			if (!m.isStatic()) { // implies it's not abstract, verified in pass 2.
				constraintViolated(o, "Referenced method '" + o.getMethodName(cpg) + "' has ACC_STATIC unset.");
			}

		}

		/** Checks if the constraints of operands of the said instruction(s) are satisfied. */
		public void visitINVOKEVIRTUAL(InvokeInstruction o) {
			// INVOKEVIRTUAL is a LoadClass; the Class where the referenced method is declared in,
			// is therefore resolved/verified.
			// INVOKEVIRTUAL is an InvokeInstruction, the argument and return types are resolved/verified,
			// too. So are the allowed method names.
			String classname = o.getClassName(cpg);
			JavaClass jc = Repository.lookupClass(classname);
			Method[] ms = jc.getMethods();
			Method m = null;
			for (int i = 0; i < ms.length; i++) {
				if (ms[i].getName().equals(o.getMethodName(cpg))
						&& Type.getReturnType(ms[i].getSignature()).equals(o.getReturnType(cpg))
						&& objarrayequals(Type.getArgumentTypes(ms[i].getSignature()), o.getArgumentTypes(cpg))) {
					m = ms[i];
					break;
				}
			}
			if (m == null) {
				constraintViolated(
						o,
						"Referenced method '"
								+ o.getMethodName(cpg)
								+ "' with expected signature not found in class '"
								+ jc.getClassName()
								+ "'. The native verfier does allow the method to be declared in some superclass or implemented interface, which the Java Virtual Machine Specification, Second Edition does not.");
			}
			if (!jc.isClass()) {
				constraintViolated(o, "Referenced class '" + jc.getClassName() + "' is an interface, but not a class as expected.");
			}

		}

		// WIDE stuff is BCEL-internal and cannot be checked here.

		/**
		 * A utility method like equals(Object) for arrays. The equality of the elements is based on their equals(Object) method
		 * instead of their object identity.
		 */
		private boolean objarrayequals(Object[] o, Object[] p) {
			if (o.length != p.length) {
				return false;
			}

			for (int i = 0; i < o.length; i++) {
				if (!o[i].equals(p[i])) {
					return false;
				}
			}

			return true;
		}

	}
}