/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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
    *
   *   https://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.statics;
  
  import java.util.Arrays;
  
  import org.apache.bcel.Const;
  import org.apache.bcel.Repository;
  import org.apache.bcel.classfile.Attribute;
  import org.apache.bcel.classfile.ClassFormatException;
  import org.apache.bcel.classfile.Code;
  import org.apache.bcel.classfile.CodeException;
  import org.apache.bcel.classfile.Constant;
  import org.apache.bcel.classfile.ConstantCP;
  import org.apache.bcel.classfile.ConstantClass;
  import org.apache.bcel.classfile.ConstantDouble;
  import org.apache.bcel.classfile.ConstantDynamic;
  import org.apache.bcel.classfile.ConstantFieldref;
  import org.apache.bcel.classfile.ConstantFloat;
  import org.apache.bcel.classfile.ConstantInteger;
  import org.apache.bcel.classfile.ConstantInterfaceMethodref;
  import org.apache.bcel.classfile.ConstantInvokeDynamic;
  import org.apache.bcel.classfile.ConstantLong;
  import org.apache.bcel.classfile.ConstantMethodref;
  import org.apache.bcel.classfile.ConstantNameAndType;
  import org.apache.bcel.classfile.ConstantString;
  import org.apache.bcel.classfile.ConstantUtf8;
  import org.apache.bcel.classfile.Field;
  import org.apache.bcel.classfile.JavaClass;
  import org.apache.bcel.classfile.LineNumber;
  import org.apache.bcel.classfile.LineNumberTable;
  import org.apache.bcel.classfile.LocalVariableTable;
  import org.apache.bcel.classfile.Method;
  import org.apache.bcel.generic.ALOAD;
  import org.apache.bcel.generic.ANEWARRAY;
  import org.apache.bcel.generic.ASTORE;
  import org.apache.bcel.generic.ATHROW;
  import org.apache.bcel.generic.ArrayType;
  import org.apache.bcel.generic.BREAKPOINT;
  import org.apache.bcel.generic.CHECKCAST;
  import org.apache.bcel.generic.ConstantPoolGen;
  import org.apache.bcel.generic.DLOAD;
  import org.apache.bcel.generic.DSTORE;
  import org.apache.bcel.generic.FLOAD;
  import org.apache.bcel.generic.FSTORE;
  import org.apache.bcel.generic.FieldInstruction;
  import org.apache.bcel.generic.GETSTATIC;
  import org.apache.bcel.generic.GotoInstruction;
  import org.apache.bcel.generic.IINC;
  import org.apache.bcel.generic.ILOAD;
  import org.apache.bcel.generic.IMPDEP1;
  import org.apache.bcel.generic.IMPDEP2;
  import org.apache.bcel.generic.INSTANCEOF;
  import org.apache.bcel.generic.INVOKEDYNAMIC;
  import org.apache.bcel.generic.INVOKEINTERFACE;
  import org.apache.bcel.generic.INVOKESPECIAL;
  import org.apache.bcel.generic.INVOKESTATIC;
  import org.apache.bcel.generic.INVOKEVIRTUAL;
  import org.apache.bcel.generic.ISTORE;
  import org.apache.bcel.generic.Instruction;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.bcel.generic.InvokeInstruction;
  import org.apache.bcel.generic.JsrInstruction;
  import org.apache.bcel.generic.LDC;
  import org.apache.bcel.generic.LDC2_W;
  import org.apache.bcel.generic.LLOAD;
  import org.apache.bcel.generic.LOOKUPSWITCH;
  import org.apache.bcel.generic.LSTORE;
  import org.apache.bcel.generic.LoadClass;
  import org.apache.bcel.generic.MULTIANEWARRAY;
  import org.apache.bcel.generic.NEW;
  import org.apache.bcel.generic.NEWARRAY;
  import org.apache.bcel.generic.ObjectType;
  import org.apache.bcel.generic.PUTSTATIC;
  import org.apache.bcel.generic.RET;
  import org.apache.bcel.generic.ReferenceType;
  import org.apache.bcel.generic.ReturnInstruction;
  import org.apache.bcel.generic.TABLESWITCH;
  import org.apache.bcel.generic.Type;
  import org.apache.bcel.verifier.PassVerifier;
  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.ClassConstraintException;
 import org.apache.bcel.verifier.exc.InvalidMethodException;
 import org.apache.bcel.verifier.exc.StaticCodeConstraintException;
 import org.apache.bcel.verifier.exc.StaticCodeInstructionConstraintException;
 import org.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.
  *
  * @see #do_verify()
  */
 public final class Pass3aVerifier extends PassVerifier {
 
     /**
      * This visitor class does the actual checking for the instruction operand's constraints.
      */
     private final class InstOperandConstraintVisitor extends org.apache.bcel.generic.EmptyVisitor {
 
         /** The ConstantPoolGen instance this Visitor operates on. */
         private final ConstantPoolGen constantPoolGen;
 
         /**
          * Constructs a new instance.
          */
         InstOperandConstraintVisitor(final ConstantPoolGen constantPoolGen) {
             this.constantPoolGen = constantPoolGen;
         }
 
         /**
          * A utility method to always raise an exception.
          */
         private void constraintViolated(final Instruction i, final String message) {
             throw new StaticCodeInstructionOperandConstraintException("Instruction " + tostring(i) + " constraint violated: " + message);
         }
 
         /**
          * Looks for the method referenced by the given invoke instruction in the given class.
          *
          * @param jc the class that defines the referenced method.
          * @param invoke the instruction that references the method.
          * @return the referenced method or null if not found.
          */
         private Method getMethod(final JavaClass jc, final InvokeInstruction invoke) {
             final Method[] ms = jc.getMethods();
             for (final Method element : ms) {
                 if (element.getName().equals(invoke.getMethodName(constantPoolGen))
                     && Type.getReturnType(element.getSignature()).equals(invoke.getReturnType(constantPoolGen))
                     && Arrays.equals(Type.getArgumentTypes(element.getSignature()), invoke.getArgumentTypes(constantPoolGen))) {
                     return element;
                 }
             }
 
             return null;
         }
 
         /**
          * Looks for the method referenced by the given invoke instruction in the given class or its super classes and super
          * interfaces.
          *
          * @param jc the class that defines the referenced method.
          * @param invoke the instruction that references the method.
          * @return the referenced method or null if not found.
          */
         private Method getMethodRecursive(final JavaClass jc, final InvokeInstruction invoke) throws ClassNotFoundException {
             Method m;
             // look in the given class
             m = getMethod(jc, invoke);
             if (m != null) {
                 // method found in given class
                 return m;
             }
             // method not found, look in super classes
             for (final JavaClass superclass : jc.getSuperClasses()) {
                 m = getMethod(superclass, invoke);
                 if (m != null) {
                     // method found in super class
                     return m;
                 }
             }
             // method not found, look in super interfaces
             for (final JavaClass superclass : jc.getInterfaces()) {
                 m = getMethod(superclass, invoke);
                 if (m != null) {
                     // method found in super interface
                     return m;
                 }
             }
             // method not found in the hierarchy
             return null;
         }
 
         private ObjectType getObjectType(final FieldInstruction o) {
             final ReferenceType rt = o.getReferenceType(constantPoolGen);
             if (rt instanceof ObjectType) {
                 return (ObjectType) rt;
             }
             constraintViolated(o, "expecting ObjectType but got " + rt);
             return null;
         }
 
         // 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.
 
         /**
          * A utility method to raise an exception if the index is not a valid constant pool index.
          */
         private void indexValid(final Instruction i, final int idx) {
             if (idx < 0 || idx >= constantPoolGen.getSize()) {
                 constraintViolated(i, "Illegal constant pool index '" + idx + "'.");
             }
         }
 
         /**
          * Utility method to return the max_locals value of the method verified by the surrounding Pass3aVerifier instance.
          */
         private int maxLocals() {
             try {
                 return Repository.lookupClass(verifier.getClassName()).getMethods()[methodNo].getCode().getMaxLocals();
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 throw new AssertionViolatedException("Missing class: " + e, e);
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitALOAD(final ALOAD o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 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. */
         @Override
         public void visitANEWARRAY(final ANEWARRAY o) {
             indexValid(o, o.getIndex());
             final Constant c = constantPoolGen.getConstant(o.getIndex());
             if (!(c instanceof ConstantClass)) {
                 constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + tostring(c) + "'.");
             }
             final Type t = o.getType(constantPoolGen);
             if (t instanceof ArrayType) {
                 final int dimensions = ((ArrayType) t).getDimensions();
                 if (dimensions > Const.MAX_ARRAY_DIMENSIONS) {
                     constraintViolated(o,
                         "Not allowed to create an array with more than " + Const.MAX_ARRAY_DIMENSIONS + " dimensions; actual: " + dimensions);
                 }
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitASTORE(final ASTORE o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 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. */
         @Override
         public void visitCHECKCAST(final CHECKCAST o) {
             indexValid(o, o.getIndex());
             final Constant c = constantPoolGen.getConstant(o.getIndex());
             if (!(c instanceof ConstantClass)) {
                 constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + tostring(c) + "'.");
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitDLOAD(final DLOAD o) {
             final 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 {
                 final int maxminus2 = maxLocals() - 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. */
         @Override
         public void visitDSTORE(final DSTORE o) {
             final 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 {
                 final int maxminus2 = maxLocals() - 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. */
         // getfield, putfield, getstatic, putstatic
         @Override
         public void visitFieldInstruction(final FieldInstruction o) {
             try {
                 indexValid(o, o.getIndex());
                 final Constant c = constantPoolGen.getConstant(o.getIndex());
                 if (!(c instanceof ConstantFieldref)) {
                     constraintViolated(o, "Indexing a constant that's not a CONSTANT_Fieldref but a '" + tostring(c) + "'.");
                 }
 
                 final String fieldName = o.getFieldName(constantPoolGen);
 
                 final JavaClass jc = Repository.lookupClass(getObjectType(o).getClassName());
                 final Field f = jc.findField(fieldName, o.getType(constantPoolGen));
                 if (f == null) {
                     constraintViolated(o, "Referenced field '" + fieldName + "' does not exist in class '" + jc.getClassName() + "'.");
                 }
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 throw new AssertionViolatedException("Missing class: " + e, e);
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitFLOAD(final FLOAD o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 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. */
         @Override
         public void visitFSTORE(final FSTORE o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 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. */
         @Override
         public void visitGETSTATIC(final GETSTATIC o) {
             try {
                 final String fieldName = o.getFieldName(constantPoolGen);
                 final JavaClass jc = Repository.lookupClass(getObjectType(o).getClassName());
                 final Field f = jc.findField(fieldName, o.getType(constantPoolGen));
                 if (f == null) {
                     throw new AssertionViolatedException("Field '" + fieldName + "' not found in " + jc.getClassName());
                 }
 
                 if (!f.isStatic()) {
                     constraintViolated(o, "Referenced field '" + f + "' is not static which it should be.");
                 }
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 throw new AssertionViolatedException("Missing class: " + e, e);
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitIINC(final IINC o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 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. */
         @Override
         public void visitILOAD(final ILOAD o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 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. */
         @Override
         public void visitINSTANCEOF(final INSTANCEOF o) {
             indexValid(o, o.getIndex());
             final Constant c = constantPoolGen.getConstant(o.getIndex());
             if (!(c instanceof ConstantClass)) {
                 constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + tostring(c) + "'.");
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitINVOKEDYNAMIC(final INVOKEDYNAMIC o) {
             throw new UnsupportedOperationException("INVOKEDYNAMIC instruction is not supported at this time");
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitInvokeInstruction(final InvokeInstruction o) {
             indexValid(o, o.getIndex());
             if (o instanceof INVOKEVIRTUAL || o instanceof INVOKESPECIAL || o instanceof INVOKESTATIC) {
                 final Constant c = constantPoolGen.getConstant(o.getIndex());
                 if (!(c instanceof ConstantMethodref)) {
                     constraintViolated(o, "Indexing a constant that's not a CONSTANT_Methodref but a '" + tostring(c) + "'.");
                 } else {
                     // Constants are okay due to pass2.
                     final ConstantNameAndType cnat = (ConstantNameAndType) constantPoolGen.getConstant(((ConstantMethodref) c).getNameAndTypeIndex());
                     final ConstantUtf8 cutf8 = (ConstantUtf8) constantPoolGen.getConstant(cnat.getNameIndex());
                     if (cutf8.getBytes().equals(Const.CONSTRUCTOR_NAME) && !(o instanceof INVOKESPECIAL)) {
                         constraintViolated(o, "Only INVOKESPECIAL is allowed to invoke instance initialization methods.");
                     }
                     if (!cutf8.getBytes().equals(Const.CONSTRUCTOR_NAME) && cutf8.getBytes().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 {
                 final Constant c = constantPoolGen.getConstant(o.getIndex());
                 if (!(c instanceof ConstantInterfaceMethodref) && !(c instanceof ConstantInvokeDynamic)) {
                     constraintViolated(o, "Indexing a constant that's not a CONSTANT_InterfaceMethodref/InvokeDynamic but a '" + tostring(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>
                 final ConstantNameAndType cnat = (ConstantNameAndType) constantPoolGen.getConstant(((ConstantCP) c).getNameAndTypeIndex());
                 final String name = ((ConstantUtf8) constantPoolGen.getConstant(cnat.getNameIndex())).getBytes();
                 if (name.equals(Const.CONSTRUCTOR_NAME)) {
                     constraintViolated(o, "Method to invoke must not be '" + Const.CONSTRUCTOR_NAME + "'.");
                 }
                 if (name.equals(Const.STATIC_INITIALIZER_NAME)) {
                     constraintViolated(o, "Method to invoke must not be '" + Const.STATIC_INITIALIZER_NAME + "'.");
                 }
             }
 
             // The LoadClassType is the method-declaring class, so we have to check the other types.
 
             Type t = o.getReturnType(constantPoolGen);
             if (t instanceof ArrayType) {
                 t = ((ArrayType) t).getBasicType();
             }
             if (t instanceof ObjectType) {
                 final Verifier v = VerifierFactory.getVerifier(((ObjectType) t).getClassName());
                 final VerificationResult vr = v.doPass2();
                 if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
                     constraintViolated(o, "Return type class/interface could not be verified successfully: '" + vr.getMessage() + "'.");
                 }
             }
 
             final Type[] ts = o.getArgumentTypes(constantPoolGen);
             for (final Type element : ts) {
                 t = element;
                 if (t instanceof ArrayType) {
                     t = ((ArrayType) t).getBasicType();
                 }
                 if (t instanceof ObjectType) {
                     final Verifier v = VerifierFactory.getVerifier(((ObjectType) t).getClassName());
                     final 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 visitINVOKEINTERFACE(final INVOKEINTERFACE o) {
             try {
                 // 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.
                 final String className = o.getClassName(constantPoolGen);
                 final JavaClass jc = Repository.lookupClass(className);
                 final Method m = getMethodRecursive(jc, o);
                 if (m == null) {
                     constraintViolated(o, "Referenced method '" + o.getMethodName(constantPoolGen) + "' with expected signature '"
                         + o.getSignature(constantPoolGen) + "' not found in class '" + jc.getClassName() + "'.");
                 }
                 if (jc.isClass()) {
                     constraintViolated(o, "Referenced class '" + jc.getClassName() + "' is a class, but not an interface as expected.");
                 }
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 throw new AssertionViolatedException("Missing class: " + e, e);
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitINVOKESPECIAL(final INVOKESPECIAL o) {
             try {
                 // 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.
                 final String className = o.getClassName(constantPoolGen);
                 final JavaClass jc = Repository.lookupClass(className);
                 final Method m = getMethodRecursive(jc, o);
                 if (m == null) {
                     constraintViolated(o, "Referenced method '" + o.getMethodName(constantPoolGen) + "' with expected signature '"
                         + o.getSignature(constantPoolGen) + "' not found in class '" + jc.getClassName() + "'.");
                 }
 
                 JavaClass current = Repository.lookupClass(verifier.getClassName());
                 if (current.isSuper() && Repository.instanceOf(current, jc) && !current.equals(jc)
                     && !o.getMethodName(constantPoolGen).equals(Const.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());
 
                         final Method[] meths = current.getMethods();
                         for (final Method meth2 : meths) {
                             if (meth2.getName().equals(o.getMethodName(constantPoolGen))
                                 && Type.getReturnType(meth2.getSignature()).equals(o.getReturnType(constantPoolGen))
                                 && Arrays.equals(Type.getArgumentTypes(meth2.getSignature()), o.getArgumentTypes(constantPoolGen))) {
                                 meth = meth2;
                                 break;
                             }
                         }
                         if (meth != null) {
                             break;
                         }
                     }
                     if (meth == null) {
                         constraintViolated(o, "ACC_SUPER special lookup procedure not successful: method '" + o.getMethodName(constantPoolGen)
                             + "' with proper signature not declared in superclass hierarchy.");
                     }
                 }
 
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 throw new AssertionViolatedException("Missing class: " + e, e);
             }
 
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitINVOKESTATIC(final INVOKESTATIC o) {
             try {
                 // 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.
                 final String className = o.getClassName(constantPoolGen);
                 final JavaClass jc = Repository.lookupClass(className);
                 final Method m = getMethodRecursive(jc, o);
                 if (m == null) {
                     constraintViolated(o, "Referenced method '" + o.getMethodName(constantPoolGen) + "' with expected signature '"
                         + o.getSignature(constantPoolGen) + "' not found in class '" + jc.getClassName() + "'.");
                 } else if (!m.isStatic()) { // implies it's not abstract, verified in pass 2.
                     constraintViolated(o, "Referenced method '" + o.getMethodName(constantPoolGen) + "' has ACC_STATIC unset.");
                 }
 
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 throw new AssertionViolatedException("Missing class: " + e, e);
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitINVOKEVIRTUAL(final INVOKEVIRTUAL o) {
             try {
                 // 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.
                 final String className = o.getClassName(constantPoolGen);
                 final JavaClass jc;
                 if (className.charAt(0) == '[') { // array type, for example invoke can be someArray.clone()
                     jc = Repository.lookupClass("java.lang.Object");
                 } else {
                     jc = Repository.lookupClass(className);
                 }
                 final Method m = getMethodRecursive(jc, o);
                 if (m == null) {
                     constraintViolated(o, "Referenced method '" + o.getMethodName(constantPoolGen) + "' with expected signature '"
                         + o.getSignature(constantPoolGen) + "' not found in class '" + jc.getClassName() + "'.");
                 }
                 if (!jc.isClass()) {
                     constraintViolated(o, "Referenced class '" + jc.getClassName() + "' is an interface, but not a class as expected.");
                 }
 
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 // throw new AssertionViolatedException("Missing class: " + e, e);
                 addMessage("Unable to verify INVOKEVITUAL as cannot load target class: " + e.getCause());
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitISTORE(final ISTORE o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 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. */
         // LDC and LDC_W (LDC_W is a subclass of LDC in BCEL's model)
         @Override
         public void visitLDC(final LDC ldc) {
             indexValid(ldc, ldc.getIndex());
             final Constant c = constantPoolGen.getConstant(ldc.getIndex());
             if (c instanceof ConstantClass) {
                 addMessage("Operand of LDC or LDC_W is CONSTANT_Class '" + tostring(c) + "' - this is only supported in JDK 1.5 and higher.");
             } else if (!(c instanceof ConstantInteger || c instanceof ConstantFloat || c instanceof ConstantString || c instanceof ConstantDynamic)) {
                 constraintViolated(ldc,
                     "Operand of LDC or LDC_W must be one of CONSTANT_Integer, CONSTANT_Float, CONSTANT_String or CONSTANT_Dynamic but is '"
                             + tostring(c) + "'.");
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         // LDC2_W
         @Override
         public void visitLDC2_W(final LDC2_W o) {
             indexValid(o, o.getIndex());
             final Constant c = constantPoolGen.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 '" + tostring(c) + "'.");
             }
             try {
                 indexValid(o, o.getIndex() + 1);
             } catch (final StaticCodeInstructionOperandConstraintException e) {
                 throw new AssertionViolatedException("Does not BCEL handle that? LDC2_W operand has a problem.", e);
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitLLOAD(final LLOAD o) {
             final 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 {
                 final int maxminus2 = maxLocals() - 2;
                 if (idx > maxminus2) {
                     constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-2 '" + maxminus2 + "'.");
                 }
             }
         }
 
         ///////////////////////////////////////////////////////////
         // 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(final LoadClass loadClass) {
             final ObjectType t = loadClass.getLoadClassType(constantPoolGen);
             if (t != null) { // null means "no class is loaded"
                 final Verifier v = VerifierFactory.getVerifier(t.getClassName());
                 final VerificationResult vr = v.doPass1();
                 if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
                     constraintViolated((Instruction) loadClass,
                             "Class '" + loadClass.getLoadClassType(constantPoolGen).getClassName() + "' is referenced, but cannot be loaded: '" + vr + "'.");
                 }
             }
         }
 
         /* 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. */
         @Override
         public void visitLOOKUPSWITCH(final LOOKUPSWITCH o) {
             final 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. */
         @Override
         public void visitLSTORE(final LSTORE o) {
             final 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 {
                 final int maxminus2 = maxLocals() - 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. */
         @Override
         public void visitMULTIANEWARRAY(final MULTIANEWARRAY o) {
             indexValid(o, o.getIndex());
             final Constant c = constantPoolGen.getConstant(o.getIndex());
             if (!(c instanceof ConstantClass)) {
                 constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + tostring(c) + "'.");
             }
             final int dimensions2create = o.getDimensions();
             if (dimensions2create < 1) {
                 constraintViolated(o, "Number of dimensions to create must be greater than zero.");
             }
             final Type t = o.getType(constantPoolGen);
             if (t instanceof ArrayType) {
                 final 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. */
         @Override
         public void visitNEW(final NEW o) {
             indexValid(o, o.getIndex());
             final Constant c = constantPoolGen.getConstant(o.getIndex());
             if (!(c instanceof ConstantClass)) {
                 constraintViolated(o, "Expecting a CONSTANT_Class operand, but found a '" + tostring(c) + "'.");
             } else {
                 final ConstantUtf8 cutf8 = (ConstantUtf8) constantPoolGen.getConstant(((ConstantClass) c).getNameIndex());
                 final Type t = Type.getType("L" + cutf8.getBytes() + ";");
                 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. */
         @Override
         public void visitNEWARRAY(final NEWARRAY o) {
             final byte t = o.getTypecode();
             if (!(t == Const.T_BOOLEAN || t == Const.T_CHAR || t == Const.T_FLOAT || t == Const.T_DOUBLE || t == Const.T_BYTE || t == Const.T_SHORT
                 || t == Const.T_INT || t == Const.T_LONG)) {
                 constraintViolated(o, "Illegal type code '" + tostring(t) + "' for 'atype' operand.");
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitPUTSTATIC(final PUTSTATIC o) {
             try {
                 final String fieldName = o.getFieldName(constantPoolGen);
                 final JavaClass jc = Repository.lookupClass(getObjectType(o).getClassName());
                 final Field f = jc.findField(fieldName, o.getType(constantPoolGen));
                 if (f == null) {
                     throw new AssertionViolatedException("Field '" + fieldName + "' not found in " + jc.getClassName());
                 }
 
                 if (f.isFinal() && !verifier.getClassName().equals(getObjectType(o).getClassName())) {
                     constraintViolated(o, "Referenced field '" + f + "' is final and must therefore be declared in the current class '"
                             + verifier.getClassName() + "' which is not the case: it is declared in '" + o.getReferenceType(constantPoolGen) + "'.");
                 }
 
                 if (!f.isStatic()) {
                     constraintViolated(o, "Referenced field '" + f + "' is not static which it should be.");
                 }
 
                 final String methName = Repository.lookupClass(verifier.getClassName()).getMethods()[methodNo].getName();
 
                 // If it's an interface, it can be set only in <clinit>.
                 if (!jc.isClass() && !methName.equals(Const.STATIC_INITIALIZER_NAME)) {
                     constraintViolated(o, "Interface field '" + f + "' must be set in a '" + Const.STATIC_INITIALIZER_NAME + "' method.");
                 }
             } catch (final ClassNotFoundException e) {
                 // FIXME: maybe not the best way to handle this
                 throw new AssertionViolatedException("Missing class: " + e, e);
             }
         }
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitRET(final RET o) {
             final int idx = o.getIndex();
             if (idx < 0) {
                 constraintViolated(o, "Index '" + idx + "' must be non-negative.");
             } else {
                 final int maxminus1 = maxLocals() - 1;
                 if (idx > maxminus1) {
                     constraintViolated(o, "Index '" + idx + "' must not be greater than max_locals-1 '" + maxminus1 + "'.");
                 }
             }
         }
 
         // WIDE stuff is BCEL-internal and cannot be checked here.
 
         /** Checks if the constraints of operands of the said instruction(s) are satisfied. */
         @Override
         public void visitTABLESWITCH(final TABLESWITCH o) {
             // "high" must be >= "low". We cannot check this, as BCEL hides
             // it from us.
         }
     }
 
     /** A small utility method returning if a given int i is in the given int[] ints. */
     private static boolean contains(final int[] ints, final int i) {
         for (final int k : ints) {
             if (k == i) {
                 return true;
             }
         }
         return false;
     }
 
     /** The Verifier that created this. */
     private final Verifier verifier;
 
     /**
      * The method number to verify. This is the index in the array returned by JavaClass.getMethods().
      */
     private final int methodNo;
 
     /**
      * 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.
      */
     private 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.
      */
     private Code code;
 
     /** Should only be instantiated by a Verifier. */
     public Pass3aVerifier(final Verifier verifier, final int methodNo) {
         this.verifier = verifier;
         this.methodNo = methodNo;
     }
 
     /**
      * 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() {
 
         final int[] instructionPositions = instructionList.getInstructionPositions();
         final int codeLength = code.getCode().length;
 
         /////////////////////
         // LineNumberTable //
         /////////////////////
         final LineNumberTable lnt = code.getLineNumberTable();
         if (lnt != null) {
             final LineNumber[] lineNumbers = lnt.getLineNumberTable();
             final IntList offsets = new IntList();
             lineNumberLoop: for (final LineNumber lineNumber : lineNumbers) { // may appear in any order.
                 for (final int instructionPosition : instructionPositions) {
                     // TODO: Make this a binary search! The instructionPositions array is naturally ordered!
                     final int offset = lineNumber.getStartPC();
                     if (instructionPosition == 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 lineNumberLoop;
                     }
                 }
                 throw new ClassConstraintException("Code attribute '" + tostring(code) + "' has a LineNumberTable attribute '" + code.getLineNumberTable()
                     + "' referring to a code offset ('" + lineNumber.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.
          */
         final Attribute[] atts = code.getAttributes();
         for (final Attribute att : atts) {
             if (att instanceof LocalVariableTable) {
                 ((LocalVariableTable) att).forEach(localVariable -> {
                     final int startpc = localVariable.getStartPC();
                     final int length = localVariable.getLength();
 
                     if (!contains(instructionPositions, startpc)) {
                         throw new ClassConstraintException("Code attribute '" + tostring(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 '" + tostring(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.
         final CodeException[] exceptionTable = code.getExceptionTable();
         for (final CodeException element : exceptionTable) {
             final int startpc = element.getStartPC();
             final int endpc = element.getEndPC();
             final int handlerpc = element.getHandlerPC();
             if (startpc >= endpc) {
                 throw new ClassConstraintException("Code attribute '" + tostring(code) + "' has an exception_table entry '" + element
                     + "' that has its start_pc ('" + startpc + "') not smaller than its end_pc ('" + endpc + "').");
             }
             if (!contains(instructionPositions, startpc)) {
                 throw new ClassConstraintException("Code attribute '" + tostring(code) + "' has an exception_table entry '" + element
                     + "' that has a non-existant bytecode offset as its start_pc ('" + startpc + "').");
             }
             if (!contains(instructionPositions, endpc) && endpc != codeLength) {
                 throw new ClassConstraintException("Code attribute '" + tostring(code) + "' has an exception_table entry '" + element
                     + "' 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 '" + tostring(code) + "' has an exception_table entry '" + element
                     + "' that has a non-existant bytecode offset as its handler_pc ('" + handlerpc + "').");
             }
         }
     }
 
     /**
      * 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() {
         try {
             if (verifier.doPass2().equals(VerificationResult.VR_OK)) {
                 // Okay, class file was loaded correctly by Pass 1
                 // and satisfies static constraints of Pass 2.
                 final JavaClass jc = Repository.lookupClass(verifier.getClassName());
                 final Method[] methods = jc.getMethods();
                 if (methodNo >= methods.length) {
                     throw new InvalidMethodException("METHOD DOES NOT EXIST!");
                 }
                 final Method method = methods[methodNo];
                 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, for example 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 (final RuntimeException re) {
                     return new VerificationResult(VerificationResult.VERIFIED_REJECTED,
                         "Bad bytecode in the code array of the Code attribute of method '" + tostring(method) + "'.");
                 }
 
                 instructionList.setPositions(true);
 
                 // Start verification.
                 VerificationResult vr = VerificationResult.VR_OK; // default
                 try {
                     delayedPass2Checks();
                 } catch (final ClassConstraintException | ClassFormatException cce) {
                     return new VerificationResult(VerificationResult.VERIFIED_REJECTED, cce.getMessage());
                 }
                 try {
                     pass3StaticInstructionChecks();
                     pass3StaticInstructionOperandsChecks();
                 } catch (final StaticCodeConstraintException | ClassFormatException scce) {
                     vr = new VerificationResult(VerificationResult.VERIFIED_REJECTED, scce.getMessage());
                 } catch (final ClassCastException cce) {
                     vr = new VerificationResult(VerificationResult.VERIFIED_REJECTED, "Class Cast Exception: " + cce.getMessage());
                 }
                 return vr;
             }
             // did not pass Pass 2.
             return VerificationResult.VR_NOTYET;
         } catch (final ClassNotFoundException e) {
             // FIXME: maybe not the best way to handle this
             throw new AssertionViolatedException("Missing class: " + e, e);
         }
     }
 
     /** Returns the method number as supplied when instantiating. */
     public int getMethodNo() {
         return methodNo;
     }
 
     /**
      * 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 >= Const.MAX_CODE_SIZE) { // length must be LESS than the max
             throw new StaticCodeInstructionConstraintException(
                 "Code array in code attribute '" + tostring(code) + "' too big: must be smaller than " + Const.MAX_CODE_SIZE + "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) {
             final Instruction i = ih.getInstruction();
             if (i instanceof IMPDEP1) {
                 throw new StaticCodeInstructionConstraintException("IMPDEP1 must not be in the code, it is an illegal instruction for _internal_ JVM use!");
             }
             if (i instanceof IMPDEP2) {
                 throw new StaticCodeInstructionConstraintException("IMPDEP2 must not be in the code, it is an illegal instruction for _internal_ JVM use!");
             }
             if (i instanceof 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.
         final Instruction last = instructionList.getEnd().getInstruction();
         if (!(last instanceof ReturnInstruction || last instanceof RET || last instanceof GotoInstruction || last instanceof 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() {
         try {
             // 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.
 
             final ConstantPoolGen cpg = new ConstantPoolGen(Repository.lookupClass(verifier.getClassName()).getConstantPool());
             final InstOperandConstraintVisitor v = new InstOperandConstraintVisitor(cpg);
 
             // Checks for the things BCEL does _not_ handle itself.
             InstructionHandle ih = instructionList.getStart();
             while (ih != null) {
                 final Instruction i = ih.getInstruction();
 
                 // An "own" constraint, due to JustIce's new definition of what "subroutine" means.
                 if (i instanceof JsrInstruction) {
                     final InstructionHandle target = ((JsrInstruction) 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 '" + tostring(ih) + "' as its target.");
                     }
                     if (!(target.getInstruction() instanceof ASTORE)) {
                         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 '" + tostring(ih) + "' targets '" + tostring(target) + "'.");
                     }
                 }
 
                 // vmspec2, page 134-137
                 ih.accept(v);
 
                 ih = ih.getNext();
             }
 
         } catch (final ClassNotFoundException e) {
             // FIXME: maybe not the best way to handle this
             throw new AssertionViolatedException("Missing class: " + e, e);
         }
     }
 
     /**
      * This method is a slightly modified version of verifier.statics.StringRepresentation.toString(final Node obj) that
      * accepts any Object, not just a Node.
      *
      * Returns the String representation of the Object obj; this is obj.toString() if it does not throw any
      * RuntimeException, or else it is a string derived only from obj's class name.
      */
     protected String tostring(final Object obj) {
         String ret;
         try {
             ret = obj.toString();
         } catch (final RuntimeException e) {
             // including ClassFormatException, trying to convert the "signature" of a ReturnaddressType LocalVariable
             // (shouldn't occur, but people do crazy things)
             String s = obj.getClass().getName();
             s = s.substring(s.lastIndexOf(".") + 1);
             ret = "<<" + s + ">>";
         }
         return ret;
     }
 }