    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 *  Unless required by applicable law or agreed to in writing, software
    012 *  distributed under the License is distributed on an "AS IS" BASIS,
    013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 *  See the License for the specific language governing permissions and
    015 *  limitations under the License.
    016 *
    017 */
    018package org.apache.bcel.verifier.structurals;
    019
    020
    021import org.apache.bcel.Const;
    022import org.apache.bcel.Repository;
    023import org.apache.bcel.classfile.Constant;
    024import org.apache.bcel.classfile.ConstantClass;
    025import org.apache.bcel.classfile.ConstantDouble;
    026import org.apache.bcel.classfile.ConstantFieldref;
    027import org.apache.bcel.classfile.ConstantFloat;
    028import org.apache.bcel.classfile.ConstantInteger;
    029import org.apache.bcel.classfile.ConstantLong;
    030import org.apache.bcel.classfile.ConstantString;
    031import org.apache.bcel.classfile.Field;
    032import org.apache.bcel.classfile.JavaClass;
    033//CHECKSTYLE:OFF (there are lots of references!)
    034import org.apache.bcel.generic.*;
    035//CHECKSTYLE:ON
    036import org.apache.bcel.verifier.VerificationResult;
    037import org.apache.bcel.verifier.Verifier;
    038import org.apache.bcel.verifier.VerifierFactory;
    039import org.apache.bcel.verifier.exc.AssertionViolatedException;
    040import org.apache.bcel.verifier.exc.StructuralCodeConstraintException;
    041
    042
    043/**
    044 * A Visitor class testing for valid preconditions of JVM instructions.
    045 * The instance of this class will throw a StructuralCodeConstraintException
    046 * instance if an instruction is visitXXX()ed which has preconditions that are
    047 * not satisfied.
    048 * TODO: Currently, the JVM's behavior concerning monitors (MONITORENTER,
    049 * MONITOREXIT) is not modeled in JustIce.
    050 *
    051 * @see StructuralCodeConstraintException
    052 */
    053public class InstConstraintVisitor extends EmptyVisitor{
    054
    055    private static final ObjectType GENERIC_ARRAY = ObjectType.getInstance(GenericArray.class.getName());
    056
    057    /**
    058     * The constructor. Constructs a new instance of this class.
    059     */
    060    public InstConstraintVisitor() {}
    061
    062    /**
    063     * The Execution Frame we're working on.
    064     *
    065     * @see #setFrame(Frame f)
    066     * @see #locals()
    067     * @see #stack()
    068     */
    069    private Frame frame = null;
    070
    071    /**
    072     * The ConstantPoolGen we're working on.
    073     *
    074     * @see #setConstantPoolGen(ConstantPoolGen cpg)
    075     */
    076    private ConstantPoolGen cpg = null;
    077
    078    /**
    079     * The MethodGen we're working on.
    080     *
    081     * @see #setMethodGen(MethodGen mg)
    082     */
    083    private MethodGen mg = null;
    084
    085    /**
    086     * The OperandStack we're working on.
    087     *
    088     * @see #setFrame(Frame f)
    089     */
    090    private OperandStack stack() {
    091        return frame.getStack();
    092    }
    093
    094    /**
    095     * The LocalVariables we're working on.
    096     *
    097     * @see #setFrame(Frame f)
    098     */
    099    private LocalVariables locals() {
    100        return frame.getLocals();
    101    }
    102
    103    /**
    104   * This method is called by the visitXXX() to notify the acceptor of this InstConstraintVisitor
    105   * that a constraint violation has occured. This is done by throwing an instance of a
    106   * StructuralCodeConstraintException.
    107   * @throws StructuralCodeConstraintException always.
    108   */
    109    private void constraintViolated(final Instruction violator, final String description) {
    110        final String fq_classname = violator.getClass().getName();
    111        throw new StructuralCodeConstraintException(
    112            "Instruction "+ fq_classname.substring(fq_classname.lastIndexOf('.')+1) +" constraint violated: " + description);
    113    }
    114
    115    /**
    116     * This returns the single instance of the InstConstraintVisitor class.
    117     * To operate correctly, other values must have been set before actually
    118     * using the instance.
    119     * Use this method for performance reasons.
    120     *
    121     * @see #setConstantPoolGen(ConstantPoolGen cpg)
    122     * @see #setMethodGen(MethodGen mg)
    123     */
    124    public void setFrame(final Frame f) { // TODO could be package-protected?
    125        this.frame = f;
    126        //if (singleInstance.mg == null || singleInstance.cpg == null)
    127        // throw new AssertionViolatedException("Forgot to set important values first.");
    128    }
    129
    130    /**
    131     * Sets the ConstantPoolGen instance needed for constraint
    132     * checking prior to execution.
    133     */
    134    public void setConstantPoolGen(final ConstantPoolGen cpg) { // TODO could be package-protected?
    135        this.cpg = cpg;
    136    }
    137
    138    /**
    139     * Sets the MethodGen instance needed for constraint
    140     * checking prior to execution.
    141     */
    142    public void setMethodGen(final MethodGen mg) {
    143        this.mg = mg;
    144    }
    145
    146    /**
    147     * Assures index is of type INT.
    148     * @throws StructuralCodeConstraintException if the above constraint is not satisfied.
    149     */
    150    private void indexOfInt(final Instruction o, final Type index) {
    151        if (! index.equals(Type.INT)) {
    152            constraintViolated(o, "The 'index' is not of type int but of type "+index+".");
    153        }
    154    }
    155
    156    /**
    157     * Assures the ReferenceType r is initialized (or Type.NULL).
    158     * Formally, this means (!(r instanceof UninitializedObjectType)), because
    159     * there are no uninitialized array types.
    160     * @throws StructuralCodeConstraintException if the above constraint is not satisfied.
    161     */
    162    private void referenceTypeIsInitialized(final Instruction o, final ReferenceType r) {
    163        if (r instanceof UninitializedObjectType) {
    164            constraintViolated(o, "Working on an uninitialized object '"+r+"'.");
    165        }
    166    }
    167
    168    /** Assures value is of type INT. */
    169    private void valueOfInt(final Instruction o, final Type value) {
    170        if (! value.equals(Type.INT)) {
    171            constraintViolated(o, "The 'value' is not of type int but of type "+value+".");
    172        }
    173    }
    174
    175    /**
    176     * Assures arrayref is of ArrayType or NULL;
    177     * returns true if and only if arrayref is non-NULL.
    178     * @throws StructuralCodeConstraintException if the above constraint is violated.
    179      */
    180    private boolean arrayrefOfArrayType(final Instruction o, final Type arrayref) {
    181        if (! ((arrayref instanceof ArrayType) || arrayref.equals(Type.NULL)) ) {
    182            constraintViolated(o, "The 'arrayref' does not refer to an array but is of type "+arrayref+".");
    183        }
    184        return arrayref instanceof ArrayType;
    185    }
    186
    187    /***************************************************************/
    188    /* MISC                                                        */
    189    /***************************************************************/
    190    /**
    191     * Ensures the general preconditions of an instruction that accesses the stack.
    192     * This method is here because BCEL has no such superinterface for the stack
    193     * accessing instructions; and there are funny unexpected exceptions in the
    194     * semantices of the superinterfaces and superclasses provided.
    195     * E.g. SWAP is a StackConsumer, but DUP_X1 is not a StackProducer.
    196     * Therefore, this method is called by all StackProducer, StackConsumer,
    197     * and StackInstruction instances via their visitXXX() method.
    198     * Unfortunately, as the superclasses and superinterfaces overlap, some instructions
    199     * cause this method to be called two or three times. [TODO: Fix this.]
    200     *
    201     * @see #visitStackConsumer(StackConsumer o)
    202     * @see #visitStackProducer(StackProducer o)
    203     * @see #visitStackInstruction(StackInstruction o)
    204     */
    205    private void _visitStackAccessor(final Instruction o) {
    206        final int consume = o.consumeStack(cpg); // Stack values are always consumed first; then produced.
    207        if (consume > stack().slotsUsed()) {
    208            constraintViolated(o,
    209                "Cannot consume "+consume+" stack slots: only "+stack().slotsUsed()+" slot(s) left on stack!\nStack:\n"+stack());
    210        }
    211
    212        final int produce = o.produceStack(cpg) - o.consumeStack(cpg); // Stack values are always consumed first; then produced.
    213        if ( produce + stack().slotsUsed() > stack().maxStack() ) {
    214            constraintViolated(o, "Cannot produce "+produce+" stack slots: only "+(stack().maxStack()-stack().slotsUsed())+
    215                    " free stack slot(s) left.\nStack:\n"+stack());
    216        }
    217    }
    218
    219    /***************************************************************/
    220    /* "generic"visitXXXX methods where XXXX is an interface       */
    221    /* therefore, we don't know the order of visiting; but we know */
    222    /* these methods are called before the visitYYYY methods below */
    223    /***************************************************************/
    224
    225    /**
    226     * Assures the generic preconditions of a LoadClass instance.
    227     * The referenced class is loaded and pass2-verified.
    228     */
    229    @Override
    230    public void visitLoadClass(final LoadClass o) {
    231        final ObjectType t = o.getLoadClassType(cpg);
    232        if (t != null) {// null means "no class is loaded"
    233            final Verifier v = VerifierFactory.getVerifier(t.getClassName());
    234            final VerificationResult vr = v.doPass2();
    235            if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
    236                constraintViolated((Instruction) o, "Class '"+o.getLoadClassType(cpg).getClassName()+
    237                    "' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
    238            }
    239        }
    240    }
    241
    242    /**
    243     * Ensures the general preconditions of a StackConsumer instance.
    244     */
    245    @Override
    246    public void visitStackConsumer(final StackConsumer o) {
    247        _visitStackAccessor((Instruction) o);
    248    }
    249
    250    /**
    251     * Ensures the general preconditions of a StackProducer instance.
    252     */
    253    @Override
    254    public void visitStackProducer(final StackProducer o) {
    255        _visitStackAccessor((Instruction) o);
    256    }
    257
    258
    259    /***************************************************************/
    260    /* "generic" visitYYYY methods where YYYY is a superclass.     */
    261    /* therefore, we know the order of visiting; we know           */
    262    /* these methods are called after the visitXXXX methods above. */
    263    /***************************************************************/
    264    /**
    265     * Ensures the general preconditions of a CPInstruction instance.
    266     */
    267    @Override
    268    public void visitCPInstruction(final CPInstruction o) {
    269        final int idx = o.getIndex();
    270        if ((idx < 0) || (idx >= cpg.getSize())) {
    271            throw new AssertionViolatedException(
    272                "Huh?! Constant pool index of instruction '"+o+"' illegal? Pass 3a should have checked this!");
    273        }
    274    }
    275
    276    /**
    277     * Ensures the general preconditions of a FieldInstruction instance.
    278     */
    279     @Override
    280    public void visitFieldInstruction(final FieldInstruction o) {
    281         // visitLoadClass(o) has been called before: Every FieldOrMethod
    282         // implements LoadClass.
    283         // visitCPInstruction(o) has been called before.
    284        // A FieldInstruction may be: GETFIELD, GETSTATIC, PUTFIELD, PUTSTATIC
    285            final Constant c = cpg.getConstant(o.getIndex());
    286            if (!(c instanceof ConstantFieldref)) {
    287                constraintViolated(o,
    288                    "Index '"+o.getIndex()+"' should refer to a CONSTANT_Fieldref_info structure, but refers to '"+c+"'.");
    289            }
    290            // the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
    291            final Type t = o.getType(cpg);
    292            if (t instanceof ObjectType) {
    293                final String name = ((ObjectType)t).getClassName();
    294                final Verifier v = VerifierFactory.getVerifier( name );
    295                final VerificationResult vr = v.doPass2();
    296                if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
    297                    constraintViolated(o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
    298                }
    299            }
    300     }
    301
    302    /**
    303     * Ensures the general preconditions of an InvokeInstruction instance.
    304     */
    305     @Override
    306    public void visitInvokeInstruction(final InvokeInstruction o) {
    307         // visitLoadClass(o) has been called before: Every FieldOrMethod
    308         // implements LoadClass.
    309         // visitCPInstruction(o) has been called before.
    310        //TODO
    311     }
    312
    313    /**
    314     * Ensures the general preconditions of a StackInstruction instance.
    315     */
    316    @Override
    317    public void visitStackInstruction(final StackInstruction o) {
    318        _visitStackAccessor(o);
    319    }
    320
    321    /**
    322     * Assures the generic preconditions of a LocalVariableInstruction instance.
    323     * That is, the index of the local variable must be valid.
    324     */
    325    @Override
    326    public void visitLocalVariableInstruction(final LocalVariableInstruction o) {
    327        if (locals().maxLocals() <= (o.getType(cpg).getSize()==1? o.getIndex() : o.getIndex()+1) ) {
    328            constraintViolated(o, "The 'index' is not a valid index into the local variable array.");
    329        }
    330    }
    331
    332    /**
    333     * Assures the generic preconditions of a LoadInstruction instance.
    334     */
    335    @Override
    336    public void visitLoadInstruction(final LoadInstruction o) {
    337        //visitLocalVariableInstruction(o) is called before, because it is more generic.
    338
    339        // LOAD instructions must not read Type.UNKNOWN
    340        if (locals().get(o.getIndex()) == Type.UNKNOWN) {
    341            constraintViolated(o, "Read-Access on local variable "+o.getIndex()+" with unknown content.");
    342        }
    343
    344        // LOAD instructions, two-slot-values at index N must have Type.UNKNOWN
    345        // as a symbol for the higher halve at index N+1
    346        // [suppose some instruction put an int at N+1--- our double at N is defective]
    347        if (o.getType(cpg).getSize() == 2) {
    348            if (locals().get(o.getIndex()+1) != Type.UNKNOWN) {
    349                constraintViolated(o,
    350                    "Reading a two-locals value from local variables "+o.getIndex()+
    351                    " and "+(o.getIndex()+1)+" where the latter one is destroyed.");
    352            }
    353        }
    354
    355        // LOAD instructions must read the correct type.
    356        if (!(o instanceof ALOAD)) {
    357            if (locals().get(o.getIndex()) != o.getType(cpg) ) {
    358                constraintViolated(o,"Local Variable type and LOADing Instruction type mismatch: Local Variable: '"+
    359                    locals().get(o.getIndex())+"'; Instruction type: '"+o.getType(cpg)+"'.");
    360            }
    361        }
    362        else{ // we deal with an ALOAD
    363            if (!(locals().get(o.getIndex()) instanceof ReferenceType)) {
    364                constraintViolated(o, "Local Variable type and LOADing Instruction type mismatch: Local Variable: '"+
    365                    locals().get(o.getIndex())+"'; Instruction expects a ReferenceType.");
    366            }
    367            // ALOAD __IS ALLOWED__ to put uninitialized objects onto the stack!
    368            //referenceTypeIsInitialized(o, (ReferenceType) (locals().get(o.getIndex())));
    369        }
    370
    371        // LOAD instructions must have enough free stack slots.
    372        if ((stack().maxStack() - stack().slotsUsed()) < o.getType(cpg).getSize()) {
    373            constraintViolated(o, "Not enough free stack slots to load a '"+o.getType(cpg)+"' onto the OperandStack.");
    374        }
    375    }
    376
    377    /**
    378     * Assures the generic preconditions of a StoreInstruction instance.
    379     */
    380    @Override
    381    public void visitStoreInstruction(final StoreInstruction o) {
    382        //visitLocalVariableInstruction(o) is called before, because it is more generic.
    383
    384        if (stack().isEmpty()) { // Don't bother about 1 or 2 stack slots used. This check is implicitly done below while type checking.
    385            constraintViolated(o, "Cannot STORE: Stack to read from is empty.");
    386        }
    387
    388        if ( !(o instanceof ASTORE) ) {
    389            if (! (stack().peek() == o.getType(cpg)) ) {// the other xSTORE types are singletons in BCEL.
    390                constraintViolated(o, "Stack top type and STOREing Instruction type mismatch: Stack top: '"+stack().peek()+
    391                    "'; Instruction type: '"+o.getType(cpg)+"'.");
    392            }
    393        }
    394        else{ // we deal with ASTORE
    395            final Type stacktop = stack().peek();
    396            if ( (!(stacktop instanceof ReferenceType)) && (!(stacktop instanceof ReturnaddressType)) ) {
    397                constraintViolated(o, "Stack top type and STOREing Instruction type mismatch: Stack top: '"+stack().peek()+
    398                    "'; Instruction expects a ReferenceType or a ReturnadressType.");
    399            }
    400            //if (stacktop instanceof ReferenceType) {
    401            //    referenceTypeIsInitialized(o, (ReferenceType) stacktop);
    402            //}
    403        }
    404    }
    405
    406    /**
    407     * Assures the generic preconditions of a ReturnInstruction instance.
    408     */
    409    @Override
    410    public void visitReturnInstruction(final ReturnInstruction o) {
    411        Type method_type = mg.getType();
    412        if (method_type == Type.BOOLEAN ||
    413            method_type == Type.BYTE ||
    414            method_type == Type.SHORT ||
    415            method_type == Type.CHAR) {
    416                method_type = Type.INT;
    417            }
    418
    419        if (o instanceof RETURN) {
    420            if (method_type != Type.VOID) {
    421                constraintViolated(o, "RETURN instruction in non-void method.");
    422            }
    423            else{
    424                return;
    425            }
    426        }
    427        if (o instanceof ARETURN) {
    428            if (method_type == Type.VOID) {
    429                constraintViolated(o, "ARETURN instruction in void method.");
    430            }
    431            if (stack().peek() == Type.NULL) {
    432                return;
    433            }
    434            if (! (stack().peek() instanceof ReferenceType)) {
    435                constraintViolated(o, "Reference type expected on top of stack, but is: '"+stack().peek()+"'.");
    436            }
    437            referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()));
    438            //ReferenceType objectref = (ReferenceType) (stack().peek());
    439            // TODO: This can only be checked if using Staerk-et-al's "set of object types" instead of a
    440            // "wider cast object type" created during verification.
    441            //if (! (objectref.isAssignmentCompatibleWith(mg.getType())) ) {
    442            //    constraintViolated(o, "Type on stack top which should be returned is a '"+stack().peek()+
    443            //    "' which is not assignment compatible with the return type of this method, '"+mg.getType()+"'.");
    444            //}
    445        }
    446        else{
    447            if (! ( method_type.equals( stack().peek() ))) {
    448                constraintViolated(o, "Current method has return type of '"+mg.getType()+"' expecting a '"+method_type+
    449                    "' on top of the stack. But stack top is a '"+stack().peek()+"'.");
    450            }
    451        }
    452    }
    453
    454    /***************************************************************/
    455    /* "special"visitXXXX methods for one type of instruction each */
    456    /***************************************************************/
    457
    458    /**
    459     * Ensures the specific preconditions of the said instruction.
    460     */
    461    @Override
    462    public void visitAALOAD(final AALOAD o) {
    463        final Type arrayref = stack().peek(1);
    464        final Type index    = stack().peek(0);
    465
    466        indexOfInt(o, index);
    467        if (arrayrefOfArrayType(o, arrayref)) {
    468            if (! (((ArrayType) arrayref).getElementType() instanceof ReferenceType)) {
    469                constraintViolated(o,
    470                    "The 'arrayref' does not refer to an array with elements of a ReferenceType but to an array of "+
    471                    ((ArrayType) arrayref).getElementType()+".");
    472            }
    473            //referenceTypeIsInitialized(o, (ReferenceType) (((ArrayType) arrayref).getElementType()));
    474        }
    475    }
    476
    477    /**
    478     * Ensures the specific preconditions of the said instruction.
    479     */
    480    @Override
    481    public void visitAASTORE(final AASTORE o) {
    482        final Type arrayref = stack().peek(2);
    483        final Type index    = stack().peek(1);
    484        final Type value    = stack().peek(0);
    485
    486        indexOfInt(o, index);
    487        if (!(value instanceof ReferenceType)) {
    488            constraintViolated(o, "The 'value' is not of a ReferenceType but of type "+value+".");
    489        }else{
    490            //referenceTypeIsInitialized(o, (ReferenceType) value);
    491        }
    492        // Don't bother further with "referenceTypeIsInitialized()", there are no arrays
    493        // of an uninitialized object type.
    494        if (arrayrefOfArrayType(o, arrayref)) {
    495            if (! (((ArrayType) arrayref).getElementType() instanceof ReferenceType)) {
    496                constraintViolated(o, "The 'arrayref' does not refer to an array with elements of a ReferenceType but to an array of "+
    497                    ((ArrayType) arrayref).getElementType()+".");
    498            }
    499            // No check for array element assignment compatibility. This is done at runtime.
    500        }
    501    }
    502
    503    /**
    504     * Ensures the specific preconditions of the said instruction.
    505     */
    506    @Override
    507    public void visitACONST_NULL(final ACONST_NULL o) {
    508        // Nothing needs to be done here.
    509    }
    510
    511    /**
    512     * Ensures the specific preconditions of the said instruction.
    513     */
    514    @Override
    515    public void visitALOAD(final ALOAD o) {
    516        //visitLoadInstruction(LoadInstruction) is called before.
    517
    518        // Nothing else needs to be done here.
    519    }
    520
    521    /**
    522     * Ensures the specific preconditions of the said instruction.
    523     */
    524    @Override
    525    public void visitANEWARRAY(final ANEWARRAY o) {
    526        if (!stack().peek().equals(Type.INT)) {
    527            constraintViolated(o, "The 'count' at the stack top is not of type '"+Type.INT+"' but of type '"+stack().peek()+"'.");
    528        // The runtime constant pool item at that index must be a symbolic reference to a class,
    529        // array, or interface type. See Pass 3a.
    530        }
    531    }
    532
    533    /**
    534     * Ensures the specific preconditions of the said instruction.
    535     */
    536    @Override
    537    public void visitARETURN(final ARETURN o) {
    538        if (! (stack().peek() instanceof ReferenceType) ) {
    539            constraintViolated(o, "The 'objectref' at the stack top is not of a ReferenceType but of type '"+stack().peek()+"'.");
    540        }
    541        final ReferenceType objectref = (ReferenceType) (stack().peek());
    542        referenceTypeIsInitialized(o, objectref);
    543
    544        // The check below should already done via visitReturnInstruction(ReturnInstruction), see there.
    545        // It cannot be done using Staerk-et-al's "set of object types" instead of a
    546        // "wider cast object type", anyway.
    547        //if (! objectref.isAssignmentCompatibleWith(mg.getReturnType() )) {
    548        //    constraintViolated(o, "The 'objectref' type "+objectref+
    549        // " at the stack top is not assignment compatible with the return type '"+mg.getReturnType()+"' of the method.");
    550        //}
    551    }
    552
    553    /**
    554     * Ensures the specific preconditions of the said instruction.
    555     */
    556    @Override
    557    public void visitARRAYLENGTH(final ARRAYLENGTH o) {
    558        final Type arrayref = stack().peek(0);
    559        arrayrefOfArrayType(o, arrayref);
    560    }
    561
    562    /**
    563     * Ensures the specific preconditions of the said instruction.
    564     */
    565    @Override
    566    public void visitASTORE(final ASTORE o) {
    567        if (! ( (stack().peek() instanceof ReferenceType) || (stack().peek() instanceof ReturnaddressType) ) ) {
    568            constraintViolated(o, "The 'objectref' is not of a ReferenceType or of ReturnaddressType but of "+stack().peek()+".");
    569        }
    570        //if (stack().peek() instanceof ReferenceType) {
    571        //    referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
    572        //}
    573    }
    574
    575    /**
    576     * Ensures the specific preconditions of the said instruction.
    577     */
    578    @Override
    579    public void visitATHROW(final ATHROW o) {
    580        try {
    581        // It's stated that 'objectref' must be of a ReferenceType --- but since Throwable is
    582        // not derived from an ArrayType, it follows that 'objectref' must be of an ObjectType or Type.NULL.
    583        if (! ((stack().peek() instanceof ObjectType) || (stack().peek().equals(Type.NULL))) ) {
    584            constraintViolated(o, "The 'objectref' is not of an (initialized) ObjectType but of type "+stack().peek()+".");
    585        }
    586
    587        // NULL is a subclass of every class, so to speak.
    588        if (stack().peek().equals(Type.NULL)) {
    589            return;
    590        }
    591
    592        final ObjectType exc = (ObjectType) (stack().peek());
    593        final ObjectType throwable = (ObjectType) (Type.getType("Ljava/lang/Throwable;"));
    594        if ( (! (exc.subclassOf(throwable)) ) && (! (exc.equals(throwable))) ) {
    595            constraintViolated(o,
    596                "The 'objectref' is not of class Throwable or of a subclass of Throwable, but of '"+stack().peek()+"'.");
    597        }
    598        } catch (final ClassNotFoundException e) {
    599        // FIXME: maybe not the best way to handle this
    600        throw new AssertionViolatedException("Missing class: " + e, e);
    601        }
    602    }
    603
    604    /**
    605     * Ensures the specific preconditions of the said instruction.
    606     */
    607    @Override
    608    public void visitBALOAD(final BALOAD o) {
    609        final Type arrayref = stack().peek(1);
    610        final Type index    = stack().peek(0);
    611        indexOfInt(o, index);
    612        if (arrayrefOfArrayType(o, arrayref)) {
    613            if (! ( (((ArrayType) arrayref).getElementType().equals(Type.BOOLEAN)) ||
    614                    (((ArrayType) arrayref).getElementType().equals(Type.BYTE)) ) ) {
    615                constraintViolated(o,
    616                    "The 'arrayref' does not refer to an array with elements of a Type.BYTE or Type.BOOLEAN but to an array of '"+
    617                    ((ArrayType) arrayref).getElementType()+"'.");
    618            }
    619        }
    620    }
    621
    622    /**
    623     * Ensures the specific preconditions of the said instruction.
    624     */
    625    @Override
    626    public void visitBASTORE(final BASTORE o) {
    627        final Type arrayref = stack().peek(2);
    628        final Type index    = stack().peek(1);
    629        final Type value    = stack().peek(0);
    630
    631        indexOfInt(o, index);
    632        valueOfInt(o, value);
    633        if (arrayrefOfArrayType(o, arrayref)) {
    634            if (! ( (((ArrayType) arrayref).getElementType().equals(Type.BOOLEAN)) ||
    635                    (((ArrayType) arrayref).getElementType().equals(Type.BYTE)) ) ) {
    636                constraintViolated(o,
    637                    "The 'arrayref' does not refer to an array with elements of a Type.BYTE or Type.BOOLEAN but to an array of '"+
    638                    ((ArrayType) arrayref).getElementType()+"'.");
    639            }
    640        }
    641    }
    642
    643    /**
    644     * Ensures the specific preconditions of the said instruction.
    645     */
    646    @Override
    647    public void visitBIPUSH(final BIPUSH o) {
    648        // Nothing to do...
    649    }
    650
    651    /**
    652     * Ensures the specific preconditions of the said instruction.
    653     */
    654    @Override
    655    public void visitBREAKPOINT(final BREAKPOINT o) {
    656        throw new AssertionViolatedException(
    657            "In this JustIce verification pass there should not occur an illegal instruction such as BREAKPOINT.");
    658    }
    659
    660    /**
    661     * Ensures the specific preconditions of the said instruction.
    662     */
    663    @Override
    664    public void visitCALOAD(final CALOAD o) {
    665        final Type arrayref = stack().peek(1);
    666        final Type index = stack().peek(0);
    667
    668        indexOfInt(o, index);
    669        arrayrefOfArrayType(o, arrayref);
    670    }
    671
    672    /**
    673     * Ensures the specific preconditions of the said instruction.
    674     */
    675    @Override
    676    public void visitCASTORE(final CASTORE o) {
    677        final Type arrayref = stack().peek(2);
    678        final Type index = stack().peek(1);
    679        final Type value = stack().peek(0);
    680
    681        indexOfInt(o, index);
    682        valueOfInt(o, value);
    683        if (arrayrefOfArrayType(o, arrayref)) {
    684            if (! ((ArrayType) arrayref).getElementType().equals(Type.CHAR) ) {
    685                constraintViolated(o, "The 'arrayref' does not refer to an array with elements of type char but to an array of type "+
    686                    ((ArrayType) arrayref).getElementType()+".");
    687            }
    688        }
    689    }
    690
    691    /**
    692     * Ensures the specific preconditions of the said instruction.
    693     */
    694    @Override
    695    public void visitCHECKCAST(final CHECKCAST o) {
    696        // The objectref must be of type reference.
    697        final Type objectref = stack().peek(0);
    698        if (!(objectref instanceof ReferenceType)) {
    699            constraintViolated(o, "The 'objectref' is not of a ReferenceType but of type "+objectref+".");
    700        }
    701        //else{
    702        //    referenceTypeIsInitialized(o, (ReferenceType) objectref);
    703        //}
    704        // The unsigned indexbyte1 and indexbyte2 are used to construct an index into the runtime constant pool of the
    705        // current class (�3.6), where the value of the index is (indexbyte1 << 8) | indexbyte2. The runtime constant
    706        // pool item at the index must be a symbolic reference to a class, array, or interface type.
    707        final Constant c = cpg.getConstant(o.getIndex());
    708        if (! (c instanceof ConstantClass)) {
    709            constraintViolated(o, "The Constant at 'index' is not a ConstantClass, but '"+c+"'.");
    710        }
    711    }
    712
    713    /**
    714     * Ensures the specific preconditions of the said instruction.
    715     */
    716    @Override
    717    public void visitD2F(final D2F o) {
    718        if (stack().peek() != Type.DOUBLE) {
    719            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    720        }
    721    }
    722
    723    /**
    724     * Ensures the specific preconditions of the said instruction.
    725     */
    726    @Override
    727    public void visitD2I(final D2I o) {
    728        if (stack().peek() != Type.DOUBLE) {
    729            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    730        }
    731    }
    732
    733    /**
    734     * Ensures the specific preconditions of the said instruction.
    735     */
    736    @Override
    737    public void visitD2L(final D2L o) {
    738        if (stack().peek() != Type.DOUBLE) {
    739            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    740        }
    741    }
    742
    743    /**
    744     * Ensures the specific preconditions of the said instruction.
    745     */
    746    @Override
    747    public void visitDADD(final DADD o) {
    748        if (stack().peek() != Type.DOUBLE) {
    749            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    750        }
    751        if (stack().peek(1) != Type.DOUBLE) {
    752            constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
    753        }
    754    }
    755
    756    /**
    757     * Ensures the specific preconditions of the said instruction.
    758     */
    759    @Override
    760    public void visitDALOAD(final DALOAD o) {
    761        indexOfInt(o, stack().peek());
    762        if (stack().peek(1) == Type.NULL) {
    763            return;
    764        }
    765        if (! (stack().peek(1) instanceof ArrayType)) {
    766            constraintViolated(o, "Stack next-to-top must be of type double[] but is '"+stack().peek(1)+"'.");
    767        }
    768        final Type t = ((ArrayType) (stack().peek(1))).getBasicType();
    769        if (t != Type.DOUBLE) {
    770            constraintViolated(o, "Stack next-to-top must be of type double[] but is '"+stack().peek(1)+"'.");
    771        }
    772    }
    773
    774    /**
    775     * Ensures the specific preconditions of the said instruction.
    776     */
    777    @Override
    778    public void visitDASTORE(final DASTORE o) {
    779        if (stack().peek() != Type.DOUBLE) {
    780            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    781        }
    782        indexOfInt(o, stack().peek(1));
    783        if (stack().peek(2) == Type.NULL) {
    784            return;
    785        }
    786        if (! (stack().peek(2) instanceof ArrayType)) {
    787            constraintViolated(o, "Stack next-to-next-to-top must be of type double[] but is '"+stack().peek(2)+"'.");
    788        }
    789        final Type t = ((ArrayType) (stack().peek(2))).getBasicType();
    790        if (t != Type.DOUBLE) {
    791            constraintViolated(o, "Stack next-to-next-to-top must be of type double[] but is '"+stack().peek(2)+"'.");
    792        }
    793    }
    794
    795    /**
    796     * Ensures the specific preconditions of the said instruction.
    797     */
    798    @Override
    799    public void visitDCMPG(final DCMPG o) {
    800        if (stack().peek() != Type.DOUBLE) {
    801            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    802        }
    803        if (stack().peek(1) != Type.DOUBLE) {
    804            constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
    805        }
    806    }
    807
    808    /**
    809     * Ensures the specific preconditions of the said instruction.
    810     */
    811    @Override
    812    public void visitDCMPL(final DCMPL o) {
    813        if (stack().peek() != Type.DOUBLE) {
    814            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    815        }
    816        if (stack().peek(1) != Type.DOUBLE) {
    817            constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
    818        }
    819    }
    820
    821    /**
    822     * Ensures the specific preconditions of the said instruction.
    823     */
    824    @Override
    825    public void visitDCONST(final DCONST o) {
    826        // There's nothing to be done here.
    827    }
    828
    829    /**
    830     * Ensures the specific preconditions of the said instruction.
    831     */
    832    @Override
    833    public void visitDDIV(final DDIV o) {
    834        if (stack().peek() != Type.DOUBLE) {
    835            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    836        }
    837        if (stack().peek(1) != Type.DOUBLE) {
    838            constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
    839        }
    840    }
    841
    842    /**
    843     * Ensures the specific preconditions of the said instruction.
    844     */
    845    @Override
    846    public void visitDLOAD(final DLOAD o) {
    847        //visitLoadInstruction(LoadInstruction) is called before.
    848
    849        // Nothing else needs to be done here.
    850    }
    851
    852    /**
    853     * Ensures the specific preconditions of the said instruction.
    854     */
    855    @Override
    856    public void visitDMUL(final DMUL o) {
    857        if (stack().peek() != Type.DOUBLE) {
    858            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    859        }
    860        if (stack().peek(1) != Type.DOUBLE) {
    861            constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
    862        }
    863    }
    864
    865    /**
    866     * Ensures the specific preconditions of the said instruction.
    867     */
    868    @Override
    869    public void visitDNEG(final DNEG o) {
    870        if (stack().peek() != Type.DOUBLE) {
    871            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    872        }
    873    }
    874
    875    /**
    876     * Ensures the specific preconditions of the said instruction.
    877     */
    878    @Override
    879    public void visitDREM(final DREM o) {
    880        if (stack().peek() != Type.DOUBLE) {
    881            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    882        }
    883        if (stack().peek(1) != Type.DOUBLE) {
    884            constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
    885        }
    886    }
    887
    888    /**
    889     * Ensures the specific preconditions of the said instruction.
    890     */
    891    @Override
    892    public void visitDRETURN(final DRETURN o) {
    893        if (stack().peek() != Type.DOUBLE) {
    894            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    895        }
    896    }
    897
    898    /**
    899     * Ensures the specific preconditions of the said instruction.
    900     */
    901    @Override
    902    public void visitDSTORE(final DSTORE o) {
    903        //visitStoreInstruction(StoreInstruction) is called before.
    904
    905        // Nothing else needs to be done here.
    906    }
    907
    908    /**
    909     * Ensures the specific preconditions of the said instruction.
    910     */
    911    @Override
    912    public void visitDSUB(final DSUB o) {
    913        if (stack().peek() != Type.DOUBLE) {
    914            constraintViolated(o, "The value at the stack top is not of type 'double', but of type '"+stack().peek()+"'.");
    915        }
    916        if (stack().peek(1) != Type.DOUBLE) {
    917            constraintViolated(o, "The value at the stack next-to-top is not of type 'double', but of type '"+stack().peek(1)+"'.");
    918        }
    919    }
    920
    921    /**
    922     * Ensures the specific preconditions of the said instruction.
    923     */
    924    @Override
    925    public void visitDUP(final DUP o) {
    926        if (stack().peek().getSize() != 1) {
    927            constraintViolated(o, "Won't DUP type on stack top '"+stack().peek()+
    928                "' because it must occupy exactly one slot, not '"+stack().peek().getSize()+"'.");
    929        }
    930    }
    931
    932    /**
    933     * Ensures the specific preconditions of the said instruction.
    934     */
    935    @Override
    936    public void visitDUP_X1(final DUP_X1 o) {
    937        if (stack().peek().getSize() != 1) {
    938            constraintViolated(o,
    939                "Type on stack top '"+stack().peek()+"' should occupy exactly one slot, not '"+stack().peek().getSize()+"'.");
    940        }
    941        if (stack().peek(1).getSize() != 1) {
    942            constraintViolated(o,
    943                "Type on stack next-to-top '"+stack().peek(1)+
    944                "' should occupy exactly one slot, not '"+stack().peek(1).getSize()+"'.");
    945        }
    946    }
    947
    948    /**
    949     * Ensures the specific preconditions of the said instruction.
    950     */
    951    @Override
    952    public void visitDUP_X2(final DUP_X2 o) {
    953        if (stack().peek().getSize() != 1) {
    954            constraintViolated(o,
    955                "Stack top type must be of size 1, but is '"+stack().peek()+"' of size '"+stack().peek().getSize()+"'.");
    956        }
    957        if (stack().peek(1).getSize() == 2) {
    958            return; // Form 2, okay.
    959        }
    960        //stack().peek(1).getSize == 1.
    961        if (stack().peek(2).getSize() != 1) {
    962            constraintViolated(o,
    963                "If stack top's size is 1 and stack next-to-top's size is 1,"+
    964                " stack next-to-next-to-top's size must also be 1, but is: '"+
    965                stack().peek(2)+"' of size '"+stack().peek(2).getSize()+"'.");
    966        }
    967    }
    968
    969    /**
    970     * Ensures the specific preconditions of the said instruction.
    971     */
    972    @Override
    973    public void visitDUP2(final DUP2 o) {
    974        if (stack().peek().getSize() == 2) {
    975            return; // Form 2, okay.
    976        }
    977        //stack().peek().getSize() == 1.
    978        if (stack().peek(1).getSize() != 1) {
    979            constraintViolated(o,
    980                "If stack top's size is 1, then stack next-to-top's size must also be 1. But it is '"+stack().peek(1)+
    981                "' of size '"+stack().peek(1).getSize()+"'.");
    982        }
    983    }
    984
    985    /**
    986     * Ensures the specific preconditions of the said instruction.
    987     */
    988    @Override
    989    public void visitDUP2_X1(final DUP2_X1 o) {
    990        if (stack().peek().getSize() == 2) {
    991            if (stack().peek(1).getSize() != 1) {
    992                constraintViolated(o, "If stack top's size is 2, then stack next-to-top's size must be 1. But it is '"+
    993                    stack().peek(1)+"' of size '"+stack().peek(1).getSize()+"'.");
    994            }
    995            else{
    996                return; // Form 2
    997            }
    998        }
    999        else{ // stack top is of size 1
    1000            if ( stack().peek(1).getSize() != 1 ) {
    1001                constraintViolated(o, "If stack top's size is 1, then stack next-to-top's size must also be 1. But it is '"+
    1002                    stack().peek(1)+"' of size '"+stack().peek(1).getSize()+"'.");
    1003            }
    1004            if ( stack().peek(2).getSize() != 1 ) {
    1005                constraintViolated(o, "If stack top's size is 1, then stack next-to-next-to-top's size must also be 1. But it is '"+
    1006                    stack().peek(2)+"' of size '"+stack().peek(2).getSize()+"'.");
    1007            }
    1008        }
    1009    }
    1010
    1011    /**
    1012     * Ensures the specific preconditions of the said instruction.
    1013     */
    1014    @Override
    1015    public void visitDUP2_X2(final DUP2_X2 o) {
    1016
    1017        if (stack().peek(0).getSize() == 2) {
    1018             if (stack().peek(1).getSize() == 2) {
    1019                return; // Form 4
    1020            }
    1021            // stack top size is 2, next-to-top's size is 1
    1022            if ( stack().peek(2).getSize() != 1 ) {
    1023                constraintViolated(o, "If stack top's size is 2 and stack-next-to-top's size is 1,"+
    1024                    " then stack next-to-next-to-top's size must also be 1. But it is '"+stack().peek(2)+
    1025                    "' of size '"+stack().peek(2).getSize()+"'.");
    1026            }
    1027            else{
    1028                return; // Form 2
    1029            }
    1030        }
    1031        else{// stack top is of size 1
    1032            if (stack().peek(1).getSize() == 1) {
    1033                if ( stack().peek(2).getSize() == 2 ) {
    1034                    return; // Form 3
    1035                }
    1036                if ( stack().peek(3).getSize() == 1) {
    1037                    return; // Form 1
    1038                }
    1039            }
    1040        }
    1041        constraintViolated(o, "The operand sizes on the stack do not match any of the four forms of usage of this instruction.");
    1042    }
    1043
    1044    /**
    1045     * Ensures the specific preconditions of the said instruction.
    1046     */
    1047    @Override
    1048    public void visitF2D(final F2D o) {
    1049        if (stack().peek() != Type.FLOAT) {
    1050            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1051        }
    1052    }
    1053
    1054    /**
    1055     * Ensures the specific preconditions of the said instruction.
    1056     */
    1057    @Override
    1058    public void visitF2I(final F2I o) {
    1059        if (stack().peek() != Type.FLOAT) {
    1060            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1061        }
    1062    }
    1063
    1064    /**
    1065     * Ensures the specific preconditions of the said instruction.
    1066     */
    1067    @Override
    1068    public void visitF2L(final F2L o) {
    1069        if (stack().peek() != Type.FLOAT) {
    1070            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1071        }
    1072    }
    1073
    1074    /**
    1075     * Ensures the specific preconditions of the said instruction.
    1076     */
    1077    @Override
    1078    public void visitFADD(final FADD o) {
    1079        if (stack().peek() != Type.FLOAT) {
    1080            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1081        }
    1082        if (stack().peek(1) != Type.FLOAT) {
    1083            constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
    1084        }
    1085    }
    1086
    1087    /**
    1088     * Ensures the specific preconditions of the said instruction.
    1089     */
    1090    @Override
    1091    public void visitFALOAD(final FALOAD o) {
    1092        indexOfInt(o, stack().peek());
    1093        if (stack().peek(1) == Type.NULL) {
    1094            return;
    1095        }
    1096        if (! (stack().peek(1) instanceof ArrayType)) {
    1097            constraintViolated(o, "Stack next-to-top must be of type float[] but is '"+stack().peek(1)+"'.");
    1098        }
    1099        final Type t = ((ArrayType) (stack().peek(1))).getBasicType();
    1100        if (t != Type.FLOAT) {
    1101            constraintViolated(o, "Stack next-to-top must be of type float[] but is '"+stack().peek(1)+"'.");
    1102        }
    1103    }
    1104
    1105    /**
    1106     * Ensures the specific preconditions of the said instruction.
    1107     */
    1108    @Override
    1109    public void visitFASTORE(final FASTORE o) {
    1110        if (stack().peek() != Type.FLOAT) {
    1111            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1112        }
    1113        indexOfInt(o, stack().peek(1));
    1114        if (stack().peek(2) == Type.NULL) {
    1115            return;
    1116        }
    1117        if (! (stack().peek(2) instanceof ArrayType)) {
    1118            constraintViolated(o, "Stack next-to-next-to-top must be of type float[] but is '"+stack().peek(2)+"'.");
    1119        }
    1120        final Type t = ((ArrayType) (stack().peek(2))).getBasicType();
    1121        if (t != Type.FLOAT) {
    1122            constraintViolated(o, "Stack next-to-next-to-top must be of type float[] but is '"+stack().peek(2)+"'.");
    1123        }
    1124    }
    1125
    1126    /**
    1127     * Ensures the specific preconditions of the said instruction.
    1128     */
    1129    @Override
    1130    public void visitFCMPG(final FCMPG o) {
    1131        if (stack().peek() != Type.FLOAT) {
    1132            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1133        }
    1134        if (stack().peek(1) != Type.FLOAT) {
    1135            constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
    1136        }
    1137    }
    1138
    1139    /**
    1140     * Ensures the specific preconditions of the said instruction.
    1141     */
    1142    @Override
    1143    public void visitFCMPL(final FCMPL o) {
    1144        if (stack().peek() != Type.FLOAT) {
    1145            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1146        }
    1147        if (stack().peek(1) != Type.FLOAT) {
    1148            constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
    1149        }
    1150    }
    1151
    1152    /**
    1153     * Ensures the specific preconditions of the said instruction.
    1154     */
    1155    @Override
    1156    public void visitFCONST(final FCONST o) {
    1157        // nothing to do here.
    1158    }
    1159
    1160    /**
    1161     * Ensures the specific preconditions of the said instruction.
    1162     */
    1163    @Override
    1164    public void visitFDIV(final FDIV o) {
    1165        if (stack().peek() != Type.FLOAT) {
    1166            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1167        }
    1168        if (stack().peek(1) != Type.FLOAT) {
    1169            constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
    1170        }
    1171    }
    1172
    1173    /**
    1174     * Ensures the specific preconditions of the said instruction.
    1175     */
    1176    @Override
    1177    public void visitFLOAD(final FLOAD o) {
    1178        //visitLoadInstruction(LoadInstruction) is called before.
    1179
    1180        // Nothing else needs to be done here.
    1181    }
    1182
    1183    /**
    1184     * Ensures the specific preconditions of the said instruction.
    1185     */
    1186    @Override
    1187    public void visitFMUL(final FMUL o) {
    1188        if (stack().peek() != Type.FLOAT) {
    1189            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1190        }
    1191        if (stack().peek(1) != Type.FLOAT) {
    1192            constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
    1193        }
    1194    }
    1195
    1196    /**
    1197     * Ensures the specific preconditions of the said instruction.
    1198     */
    1199    @Override
    1200    public void visitFNEG(final FNEG o) {
    1201        if (stack().peek() != Type.FLOAT) {
    1202            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1203        }
    1204    }
    1205
    1206    /**
    1207     * Ensures the specific preconditions of the said instruction.
    1208     */
    1209    @Override
    1210    public void visitFREM(final FREM o) {
    1211        if (stack().peek() != Type.FLOAT) {
    1212            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1213        }
    1214        if (stack().peek(1) != Type.FLOAT) {
    1215            constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
    1216        }
    1217    }
    1218
    1219    /**
    1220     * Ensures the specific preconditions of the said instruction.
    1221     */
    1222    @Override
    1223    public void visitFRETURN(final FRETURN o) {
    1224        if (stack().peek() != Type.FLOAT) {
    1225            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1226        }
    1227    }
    1228
    1229    /**
    1230     * Ensures the specific preconditions of the said instruction.
    1231     */
    1232    @Override
    1233    public void visitFSTORE(final FSTORE o) {
    1234        //visitStoreInstruction(StoreInstruction) is called before.
    1235
    1236        // Nothing else needs to be done here.
    1237    }
    1238
    1239    /**
    1240     * Ensures the specific preconditions of the said instruction.
    1241     */
    1242    @Override
    1243    public void visitFSUB(final FSUB o) {
    1244        if (stack().peek() != Type.FLOAT) {
    1245            constraintViolated(o, "The value at the stack top is not of type 'float', but of type '"+stack().peek()+"'.");
    1246        }
    1247        if (stack().peek(1) != Type.FLOAT) {
    1248            constraintViolated(o, "The value at the stack next-to-top is not of type 'float', but of type '"+stack().peek(1)+"'.");
    1249        }
    1250    }
    1251
    1252    private ObjectType getObjectType(final FieldInstruction o) {
    1253        final ReferenceType rt = o.getReferenceType(cpg);
    1254        if(rt instanceof ObjectType) {
    1255            return (ObjectType)rt;
    1256        }
    1257        constraintViolated(o, "expecting ObjectType but got "+rt);
    1258        return null;
    1259    }
    1260
    1261    /**
    1262     * Ensures the specific preconditions of the said instruction.
    1263     */
    1264    @Override
    1265    public void visitGETFIELD(final GETFIELD o) {
    1266        try {
    1267        final Type objectref = stack().peek();
    1268        if (! ( (objectref instanceof ObjectType) || (objectref == Type.NULL) ) ) {
    1269            constraintViolated(o, "Stack top should be an object reference that's not an array reference, but is '"+objectref+"'.");
    1270        }
    1271
    1272        final String field_name = o.getFieldName(cpg);
    1273
    1274        final JavaClass jc = Repository.lookupClass(getObjectType(o).getClassName());
    1275        Field[] fields = jc.getFields();
    1276        Field f = null;
    1277        for (final Field field : fields) {
    1278            if (field.getName().equals(field_name)) {
    1279                  final Type f_type = Type.getType(field.getSignature());
    1280                  final Type o_type = o.getType(cpg);
    1281                    /* TODO: Check if assignment compatibility is sufficient.
    1282                   * What does Sun do?
    1283                   */
    1284                  if (f_type.equals(o_type)) {
    1285                        f = field;
    1286                        break;
    1287                    }
    1288            }
    1289        }
    1290
    1291        if (f == null) {
    1292            final JavaClass[] superclasses = jc.getSuperClasses();
    1293            outer:
    1294            for (final JavaClass superclass : superclasses) {
    1295                fields = superclass.getFields();
    1296                for (final Field field : fields) {
    1297                    if (field.getName().equals(field_name)) {
    1298                        final Type f_type = Type.getType(field.getSignature());
    1299                        final Type o_type = o.getType(cpg);
    1300                        if (f_type.equals(o_type)) {
    1301                            f = field;
    1302                            if ((f.getAccessFlags() & (Const.ACC_PUBLIC | Const.ACC_PROTECTED)) == 0) {
    1303                                f = null;
    1304                            }
    1305                            break outer;
    1306                        }
    1307                    }
    1308                }
    1309            }
    1310            if (f == null) {
    1311                throw new AssertionViolatedException("Field '" + field_name + "' not found in " + jc.getClassName());
    1312            }
    1313        }
    1314
    1315        if (f.isProtected()) {
    1316            final ObjectType classtype = getObjectType(o);
    1317            final ObjectType curr = ObjectType.getInstance(mg.getClassName());
    1318
    1319            if (    classtype.equals(curr) ||
    1320                        curr.subclassOf(classtype)    ) {
    1321                final Type t = stack().peek();
    1322                if (t == Type.NULL) {
    1323                    return;
    1324                }
    1325                if (! (t instanceof ObjectType) ) {
    1326                    constraintViolated(o, "The 'objectref' must refer to an object that's not an array. Found instead: '"+t+"'.");
    1327                }
    1328                final ObjectType objreftype = (ObjectType) t;
    1329                if (! ( objreftype.equals(curr) ||
    1330                            objreftype.subclassOf(curr) ) ) {
    1331                    //TODO: One day move to Staerk-et-al's "Set of object types" instead of "wider" object types
    1332                    //      created during the verification.
    1333                    //      "Wider" object types don't allow us to check for things like that below.
    1334                    //constraintViolated(o, "The referenced field has the ACC_PROTECTED modifier, "+
    1335                    // "and it's a member of the current class or a superclass of the current class."+
    1336                    // " However, the referenced object type '"+stack().peek()+
    1337                    // "' is not the current class or a subclass of the current class.");
    1338                }
    1339            }
    1340        }
    1341
    1342        // TODO: Could go into Pass 3a.
    1343        if (f.isStatic()) {
    1344            constraintViolated(o, "Referenced field '"+f+"' is static which it shouldn't be.");
    1345        }
    1346
    1347        } catch (final ClassNotFoundException e) {
    1348        // FIXME: maybe not the best way to handle this
    1349        throw new AssertionViolatedException("Missing class: " + e, e);
    1350        }
    1351    }
    1352
    1353    /**
    1354     * Ensures the specific preconditions of the said instruction.
    1355     */
    1356    @Override
    1357    public void visitGETSTATIC(final GETSTATIC o) {
    1358        // Field must be static: see Pass 3a.
    1359    }
    1360
    1361    /**
    1362     * Ensures the specific preconditions of the said instruction.
    1363     */
    1364    @Override
    1365    public void visitGOTO(final GOTO o) {
    1366        // nothing to do here.
    1367    }
    1368
    1369    /**
    1370     * Ensures the specific preconditions of the said instruction.
    1371     */
    1372    @Override
    1373    public void visitGOTO_W(final GOTO_W o) {
    1374        // nothing to do here.
    1375    }
    1376
    1377    /**
    1378     * Ensures the specific preconditions of the said instruction.
    1379     */
    1380    @Override
    1381    public void visitI2B(final I2B o) {
    1382        if (stack().peek() != Type.INT) {
    1383            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1384        }
    1385    }
    1386
    1387    /**
    1388     * Ensures the specific preconditions of the said instruction.
    1389     */
    1390    @Override
    1391    public void visitI2C(final I2C o) {
    1392        if (stack().peek() != Type.INT) {
    1393            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1394        }
    1395    }
    1396
    1397    /**
    1398     * Ensures the specific preconditions of the said instruction.
    1399     */
    1400    @Override
    1401    public void visitI2D(final I2D o) {
    1402        if (stack().peek() != Type.INT) {
    1403            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1404        }
    1405    }
    1406
    1407    /**
    1408     * Ensures the specific preconditions of the said instruction.
    1409     */
    1410    @Override
    1411    public void visitI2F(final I2F o) {
    1412        if (stack().peek() != Type.INT) {
    1413            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1414        }
    1415    }
    1416
    1417    /**
    1418     * Ensures the specific preconditions of the said instruction.
    1419     */
    1420    @Override
    1421    public void visitI2L(final I2L o) {
    1422        if (stack().peek() != Type.INT) {
    1423            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1424        }
    1425    }
    1426
    1427    /**
    1428     * Ensures the specific preconditions of the said instruction.
    1429     */
    1430    @Override
    1431    public void visitI2S(final I2S o) {
    1432        if (stack().peek() != Type.INT) {
    1433            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1434        }
    1435    }
    1436
    1437    /**
    1438     * Ensures the specific preconditions of the said instruction.
    1439     */
    1440    @Override
    1441    public void visitIADD(final IADD o) {
    1442        if (stack().peek() != Type.INT) {
    1443            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1444        }
    1445        if (stack().peek(1) != Type.INT) {
    1446            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1447        }
    1448    }
    1449
    1450    /**
    1451     * Ensures the specific preconditions of the said instruction.
    1452     */
    1453    @Override
    1454    public void visitIALOAD(final IALOAD o) {
    1455        indexOfInt(o, stack().peek());
    1456        if (stack().peek(1) == Type.NULL) {
    1457            return;
    1458        }
    1459        if (! (stack().peek(1) instanceof ArrayType)) {
    1460            constraintViolated(o, "Stack next-to-top must be of type int[] but is '"+stack().peek(1)+"'.");
    1461        }
    1462        final Type t = ((ArrayType) (stack().peek(1))).getBasicType();
    1463        if (t != Type.INT) {
    1464            constraintViolated(o, "Stack next-to-top must be of type int[] but is '"+stack().peek(1)+"'.");
    1465        }
    1466    }
    1467
    1468    /**
    1469     * Ensures the specific preconditions of the said instruction.
    1470     */
    1471    @Override
    1472    public void visitIAND(final IAND o) {
    1473        if (stack().peek() != Type.INT) {
    1474            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1475        }
    1476        if (stack().peek(1) != Type.INT) {
    1477            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1478        }
    1479    }
    1480
    1481    /**
    1482     * Ensures the specific preconditions of the said instruction.
    1483     */
    1484    @Override
    1485    public void visitIASTORE(final IASTORE o) {
    1486        if (stack().peek() != Type.INT) {
    1487            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1488        }
    1489        indexOfInt(o, stack().peek(1));
    1490        if (stack().peek(2) == Type.NULL) {
    1491            return;
    1492        }
    1493        if (! (stack().peek(2) instanceof ArrayType)) {
    1494            constraintViolated(o, "Stack next-to-next-to-top must be of type int[] but is '"+stack().peek(2)+"'.");
    1495        }
    1496        final Type t = ((ArrayType) (stack().peek(2))).getBasicType();
    1497        if (t != Type.INT) {
    1498            constraintViolated(o, "Stack next-to-next-to-top must be of type int[] but is '"+stack().peek(2)+"'.");
    1499        }
    1500    }
    1501
    1502    /**
    1503     * Ensures the specific preconditions of the said instruction.
    1504     */
    1505    @Override
    1506    public void visitICONST(final ICONST o) {
    1507        //nothing to do here.
    1508    }
    1509
    1510    /**
    1511     * Ensures the specific preconditions of the said instruction.
    1512     */
    1513    @Override
    1514    public void visitIDIV(final IDIV o) {
    1515        if (stack().peek() != Type.INT) {
    1516            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1517        }
    1518        if (stack().peek(1) != Type.INT) {
    1519            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1520        }
    1521    }
    1522
    1523    /**
    1524     * Ensures the specific preconditions of the said instruction.
    1525     */
    1526    @Override
    1527    public void visitIF_ACMPEQ(final IF_ACMPEQ o) {
    1528        if (!(stack().peek() instanceof ReferenceType)) {
    1529            constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
    1530        }
    1531        //referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
    1532
    1533        if (!(stack().peek(1) instanceof ReferenceType)) {
    1534            constraintViolated(o, "The value at the stack next-to-top is not of a ReferenceType, but of type '"+stack().peek(1)+"'.");
    1535        }
    1536        //referenceTypeIsInitialized(o, (ReferenceType) (stack().peek(1)) );
    1537
    1538    }
    1539
    1540    /**
    1541     * Ensures the specific preconditions of the said instruction.
    1542     */
    1543    @Override
    1544    public void visitIF_ACMPNE(final IF_ACMPNE o) {
    1545        if (!(stack().peek() instanceof ReferenceType)) {
    1546            constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
    1547            //referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
    1548        }
    1549        if (!(stack().peek(1) instanceof ReferenceType)) {
    1550            constraintViolated(o, "The value at the stack next-to-top is not of a ReferenceType, but of type '"+stack().peek(1)+"'.");
    1551            //referenceTypeIsInitialized(o, (ReferenceType) (stack().peek(1)) );
    1552        }
    1553    }
    1554
    1555    /**
    1556     * Ensures the specific preconditions of the said instruction.
    1557     */
    1558    @Override
    1559    public void visitIF_ICMPEQ(final IF_ICMPEQ o) {
    1560        if (stack().peek() != Type.INT) {
    1561            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1562        }
    1563        if (stack().peek(1) != Type.INT) {
    1564            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1565        }
    1566    }
    1567
    1568    /**
    1569     * Ensures the specific preconditions of the said instruction.
    1570     */
    1571    @Override
    1572    public void visitIF_ICMPGE(final IF_ICMPGE o) {
    1573        if (stack().peek() != Type.INT) {
    1574            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1575        }
    1576        if (stack().peek(1) != Type.INT) {
    1577            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1578        }
    1579    }
    1580
    1581    /**
    1582     * Ensures the specific preconditions of the said instruction.
    1583     */
    1584    @Override
    1585    public void visitIF_ICMPGT(final IF_ICMPGT o) {
    1586        if (stack().peek() != Type.INT) {
    1587            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1588        }
    1589        if (stack().peek(1) != Type.INT) {
    1590            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1591        }
    1592    }
    1593
    1594    /**
    1595     * Ensures the specific preconditions of the said instruction.
    1596     */
    1597    @Override
    1598    public void visitIF_ICMPLE(final IF_ICMPLE o) {
    1599        if (stack().peek() != Type.INT) {
    1600            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1601        }
    1602        if (stack().peek(1) != Type.INT) {
    1603            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1604        }
    1605    }
    1606
    1607    /**
    1608     * Ensures the specific preconditions of the said instruction.
    1609     */
    1610    @Override
    1611    public void visitIF_ICMPLT(final IF_ICMPLT o) {
    1612        if (stack().peek() != Type.INT) {
    1613            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1614        }
    1615        if (stack().peek(1) != Type.INT) {
    1616            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1617        }
    1618    }
    1619
    1620    /**
    1621     * Ensures the specific preconditions of the said instruction.
    1622     */
    1623    @Override
    1624    public void visitIF_ICMPNE(final IF_ICMPNE o) {
    1625        if (stack().peek() != Type.INT) {
    1626            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1627        }
    1628        if (stack().peek(1) != Type.INT) {
    1629            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1630        }
    1631    }
    1632
    1633    /**
    1634     * Ensures the specific preconditions of the said instruction.
    1635     */
    1636    @Override
    1637    public void visitIFEQ(final IFEQ o) {
    1638        if (stack().peek() != Type.INT) {
    1639            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1640        }
    1641    }
    1642
    1643    /**
    1644     * Ensures the specific preconditions of the said instruction.
    1645     */
    1646    @Override
    1647    public void visitIFGE(final IFGE o) {
    1648        if (stack().peek() != Type.INT) {
    1649            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1650        }
    1651    }
    1652
    1653    /**
    1654     * Ensures the specific preconditions of the said instruction.
    1655     */
    1656    @Override
    1657    public void visitIFGT(final IFGT o) {
    1658        if (stack().peek() != Type.INT) {
    1659            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1660        }
    1661    }
    1662
    1663    /**
    1664     * Ensures the specific preconditions of the said instruction.
    1665     */
    1666    @Override
    1667    public void visitIFLE(final IFLE o) {
    1668        if (stack().peek() != Type.INT) {
    1669            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1670        }
    1671    }
    1672
    1673    /**
    1674     * Ensures the specific preconditions of the said instruction.
    1675     */
    1676    @Override
    1677    public void visitIFLT(final IFLT o) {
    1678        if (stack().peek() != Type.INT) {
    1679            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1680        }
    1681    }
    1682
    1683    /**
    1684     * Ensures the specific preconditions of the said instruction.
    1685     */
    1686    @Override
    1687    public void visitIFNE(final IFNE o) {
    1688        if (stack().peek() != Type.INT) {
    1689            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1690        }
    1691    }
    1692
    1693    /**
    1694     * Ensures the specific preconditions of the said instruction.
    1695     */
    1696    @Override
    1697    public void visitIFNONNULL(final IFNONNULL o) {
    1698        if (!(stack().peek() instanceof ReferenceType)) {
    1699            constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
    1700        }
    1701        referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
    1702    }
    1703
    1704    /**
    1705     * Ensures the specific preconditions of the said instruction.
    1706     */
    1707    @Override
    1708    public void visitIFNULL(final IFNULL o) {
    1709        if (!(stack().peek() instanceof ReferenceType)) {
    1710            constraintViolated(o, "The value at the stack top is not of a ReferenceType, but of type '"+stack().peek()+"'.");
    1711        }
    1712        referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
    1713    }
    1714
    1715    /**
    1716     * Ensures the specific preconditions of the said instruction.
    1717     */
    1718    @Override
    1719    public void visitIINC(final IINC o) {
    1720        // Mhhh. In BCEL, at this time "IINC" is not a LocalVariableInstruction.
    1721        if (locals().maxLocals() <= (o.getType(cpg).getSize()==1? o.getIndex() : o.getIndex()+1) ) {
    1722            constraintViolated(o, "The 'index' is not a valid index into the local variable array.");
    1723        }
    1724
    1725        indexOfInt(o, locals().get(o.getIndex()));
    1726    }
    1727
    1728    /**
    1729     * Ensures the specific preconditions of the said instruction.
    1730     */
    1731    @Override
    1732    public void visitILOAD(final ILOAD o) {
    1733        // All done by visitLocalVariableInstruction(), visitLoadInstruction()
    1734    }
    1735
    1736    /**
    1737     * Ensures the specific preconditions of the said instruction.
    1738     */
    1739    @Override
    1740    public void visitIMPDEP1(final IMPDEP1 o) {
    1741        throw new AssertionViolatedException(
    1742            "In this JustIce verification pass there should not occur an illegal instruction such as IMPDEP1.");
    1743    }
    1744
    1745    /**
    1746     * Ensures the specific preconditions of the said instruction.
    1747     */
    1748    @Override
    1749    public void visitIMPDEP2(final IMPDEP2 o) {
    1750        throw new AssertionViolatedException(
    1751            "In this JustIce verification pass there should not occur an illegal instruction such as IMPDEP2.");
    1752    }
    1753
    1754    /**
    1755     * Ensures the specific preconditions of the said instruction.
    1756     */
    1757    @Override
    1758    public void visitIMUL(final IMUL o) {
    1759        if (stack().peek() != Type.INT) {
    1760            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1761        }
    1762        if (stack().peek(1) != Type.INT) {
    1763            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    1764        }
    1765    }
    1766
    1767    /**
    1768     * Ensures the specific preconditions of the said instruction.
    1769     */
    1770    @Override
    1771    public void visitINEG(final INEG o) {
    1772        if (stack().peek() != Type.INT) {
    1773            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    1774        }
    1775    }
    1776
    1777    /**
    1778     * Ensures the specific preconditions of the said instruction.
    1779     */
    1780    @Override
    1781    public void visitINSTANCEOF(final INSTANCEOF o) {
    1782        // The objectref must be of type reference.
    1783        final Type objectref = stack().peek(0);
    1784        if (!(objectref instanceof ReferenceType)) {
    1785            constraintViolated(o, "The 'objectref' is not of a ReferenceType but of type "+objectref+".");
    1786        }
    1787        //else{
    1788        //    referenceTypeIsInitialized(o, (ReferenceType) objectref);
    1789        //}
    1790        // The unsigned indexbyte1 and indexbyte2 are used to construct an index into the runtime constant pool of the
    1791        // current class (�3.6), where the value of the index is (indexbyte1 << 8) | indexbyte2. The runtime constant
    1792        // pool item at the index must be a symbolic reference to a class, array, or interface type.
    1793        final Constant c = cpg.getConstant(o.getIndex());
    1794        if (! (c instanceof ConstantClass)) {
    1795            constraintViolated(o, "The Constant at 'index' is not a ConstantClass, but '"+c+"'.");
    1796        }
    1797    }
    1798
    1799    /**
    1800     * Ensures the specific preconditions of the said instruction.
    1801     * @since 6.0
    1802     */
    1803    @Override
    1804    public void visitINVOKEDYNAMIC(final INVOKEDYNAMIC o) {
    1805        throw new UnsupportedOperationException("INVOKEDYNAMIC instruction is not supported at this time");
    1806    }
    1807
    1808    /**
    1809     * Ensures the specific preconditions of the said instruction.
    1810     */
    1811    @Override
    1812    public void visitINVOKEINTERFACE(final INVOKEINTERFACE o) {
    1813        // Method is not native, otherwise pass 3 would not happen.
    1814
    1815        final int count = o.getCount();
    1816        if (count == 0) {
    1817            constraintViolated(o, "The 'count' argument must not be 0.");
    1818        }
    1819        // It is a ConstantInterfaceMethodref, Pass 3a made it sure.
    1820        // TODO: Do we want to do anything with it?
    1821        //ConstantInterfaceMethodref cimr = (ConstantInterfaceMethodref) (cpg.getConstant(o.getIndex()));
    1822
    1823        // the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
    1824
    1825        final Type t = o.getType(cpg);
    1826        if (t instanceof ObjectType) {
    1827            final String name = ((ObjectType)t).getClassName();
    1828            final Verifier v = VerifierFactory.getVerifier( name );
    1829            final VerificationResult vr = v.doPass2();
    1830            if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
    1831                constraintViolated(o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
    1832            }
    1833        }
    1834
    1835
    1836        final Type[] argtypes = o.getArgumentTypes(cpg);
    1837        final int nargs = argtypes.length;
    1838
    1839        for (int i=nargs-1; i>=0; i--) {
    1840            final Type fromStack = stack().peek( (nargs-1) - i );    // 0 to nargs-1
    1841            Type fromDesc = argtypes[i];
    1842            if (fromDesc == Type.BOOLEAN ||
    1843                    fromDesc == Type.BYTE ||
    1844                    fromDesc == Type.CHAR ||
    1845                    fromDesc == Type.SHORT) {
    1846                fromDesc = Type.INT;
    1847            }
    1848            if (! fromStack.equals(fromDesc)) {
    1849                if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType) {
    1850                    final ReferenceType rFromStack = (ReferenceType) fromStack;
    1851                    //ReferenceType rFromDesc = (ReferenceType) fromDesc;
    1852                    // TODO: This can only be checked when using Staerk-et-al's "set of object types"
    1853                    // instead of a "wider cast object type" created during verification.
    1854                    //if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ) {
    1855                    //    constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+
    1856                    //    "' on the stack (which is not assignment compatible).");
    1857                    //}
    1858                    referenceTypeIsInitialized(o, rFromStack);
    1859                }
    1860                else{
    1861                    constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
    1862                }
    1863            }
    1864        }
    1865
    1866        Type objref = stack().peek(nargs);
    1867        if (objref == Type.NULL) {
    1868            return;
    1869        }
    1870        if (! (objref instanceof ReferenceType) ) {
    1871            constraintViolated(o, "Expecting a reference type as 'objectref' on the stack, not a '"+objref+"'.");
    1872        }
    1873        referenceTypeIsInitialized(o, (ReferenceType) objref);
    1874        if (!(objref instanceof ObjectType)) {
    1875            if (!(objref instanceof ArrayType)) { // could be a ReturnaddressType
    1876                constraintViolated(o, "Expecting an ObjectType as 'objectref' on the stack, not a '"+objref+"'.");
    1877            }
    1878            else{
    1879                objref = GENERIC_ARRAY;
    1880            }
    1881        }
    1882
    1883        // String objref_classname = ((ObjectType) objref).getClassName();
    1884        // String theInterface = o.getClassName(cpg);
    1885        // TODO: This can only be checked if we're using Staerk-et-al's "set of object types"
    1886        //       instead of "wider cast object types" generated during verification.
    1887        //if ( ! Repository.implementationOf(objref_classname, theInterface) ) {
    1888        //    constraintViolated(o, "The 'objref' item '"+objref+"' does not implement '"+theInterface+"' as expected.");
    1889        //}
    1890
    1891        int counted_count = 1; // 1 for the objectref
    1892        for (int i=0; i<nargs; i++) {
    1893            counted_count += argtypes[i].getSize();
    1894        }
    1895        if (count != counted_count) {
    1896            constraintViolated(o, "The 'count' argument should probably read '"+counted_count+"' but is '"+count+"'.");
    1897        }
    1898    }
    1899
    1900    /**
    1901     * Ensures the specific preconditions of the said instruction.
    1902     */
    1903    @Override
    1904    public void visitINVOKESPECIAL(final INVOKESPECIAL o) {
    1905        try {
    1906        // Don't init an object twice.
    1907        if ( (o.getMethodName(cpg).equals(Const.CONSTRUCTOR_NAME)) &&
    1908             (!(stack().peek(o.getArgumentTypes(cpg).length) instanceof UninitializedObjectType)) ) {
    1909            constraintViolated(o, "Possibly initializing object twice."+
    1910                 " A valid instruction sequence must not have an uninitialized object on the operand stack or in a local variable"+
    1911                 " during a backwards branch, or in a local variable in code protected by an exception handler."+
    1912                 " Please see The Java Virtual Machine Specification, Second Edition, 4.9.4 (pages 147 and 148) for details.");
    1913        }
    1914
    1915        // the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
    1916
    1917        final Type t = o.getType(cpg);
    1918        if (t instanceof ObjectType) {
    1919            final String name = ((ObjectType)t).getClassName();
    1920            final Verifier v = VerifierFactory.getVerifier( name );
    1921            final VerificationResult vr = v.doPass2();
    1922            if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
    1923                constraintViolated(o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
    1924            }
    1925        }
    1926
    1927
    1928        final Type[] argtypes = o.getArgumentTypes(cpg);
    1929        final int nargs = argtypes.length;
    1930
    1931        for (int i=nargs-1; i>=0; i--) {
    1932            final Type fromStack = stack().peek( (nargs-1) - i );    // 0 to nargs-1
    1933            Type fromDesc = argtypes[i];
    1934            if (fromDesc == Type.BOOLEAN ||
    1935                    fromDesc == Type.BYTE ||
    1936                    fromDesc == Type.CHAR ||
    1937                    fromDesc == Type.SHORT) {
    1938                fromDesc = Type.INT;
    1939            }
    1940            if (! fromStack.equals(fromDesc)) {
    1941                if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType) {
    1942                    final ReferenceType rFromStack = (ReferenceType) fromStack;
    1943                    final ReferenceType rFromDesc = (ReferenceType) fromDesc;
    1944                    // TODO: This can only be checked using Staerk-et-al's "set of object types", not
    1945                    // using a "wider cast object type".
    1946                    if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ) {
    1947                        constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+
    1948                            "' on the stack (which is not assignment compatible).");
    1949                    }
    1950                    referenceTypeIsInitialized(o, rFromStack);
    1951                }
    1952                else{
    1953                    constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
    1954                }
    1955            }
    1956        }
    1957
    1958        Type objref = stack().peek(nargs);
    1959        if (objref == Type.NULL) {
    1960            return;
    1961        }
    1962        if (! (objref instanceof ReferenceType) ) {
    1963            constraintViolated(o, "Expecting a reference type as 'objectref' on the stack, not a '"+objref+"'.");
    1964        }
    1965        String objref_classname = null;
    1966        if ( !(o.getMethodName(cpg).equals(Const.CONSTRUCTOR_NAME))) {
    1967            referenceTypeIsInitialized(o, (ReferenceType) objref);
    1968            if (!(objref instanceof ObjectType)) {
    1969                if (!(objref instanceof ArrayType)) { // could be a ReturnaddressType
    1970                    constraintViolated(o, "Expecting an ObjectType as 'objectref' on the stack, not a '"+objref+"'.");
    1971                }
    1972                else{
    1973                    objref = GENERIC_ARRAY;
    1974                }
    1975            }
    1976
    1977            objref_classname = ((ObjectType) objref).getClassName();
    1978        }
    1979        else{
    1980            if (!(objref instanceof UninitializedObjectType)) {
    1981                constraintViolated(o, "Expecting an UninitializedObjectType as 'objectref' on the stack, not a '"+objref+
    1982                    "'. Otherwise, you couldn't invoke a method since an array has no methods (not to speak of a return address).");
    1983            }
    1984            objref_classname = ((UninitializedObjectType) objref).getInitialized().getClassName();
    1985        }
    1986
    1987
    1988        final String theClass = o.getClassName(cpg);
    1989        if ( ! Repository.instanceOf(objref_classname, theClass) ) {
    1990            constraintViolated(o, "The 'objref' item '"+objref+"' does not implement '"+theClass+"' as expected.");
    1991        }
    1992
    1993        } catch (final ClassNotFoundException e) {
    1994        // FIXME: maybe not the best way to handle this
    1995        throw new AssertionViolatedException("Missing class: " + e, e);
    1996        }
    1997    }
    1998
    1999    /**
    2000     * Ensures the specific preconditions of the said instruction.
    2001     */
    2002    @Override
    2003    public void visitINVOKESTATIC(final INVOKESTATIC o) {
    2004        try {
    2005        // Method is not native, otherwise pass 3 would not happen.
    2006
    2007        final Type t = o.getType(cpg);
    2008        if (t instanceof ObjectType) {
    2009            final String name = ((ObjectType)t).getClassName();
    2010            final Verifier v = VerifierFactory.getVerifier( name );
    2011            final VerificationResult vr = v.doPass2();
    2012            if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
    2013                constraintViolated(o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
    2014            }
    2015        }
    2016
    2017        final Type[] argtypes = o.getArgumentTypes(cpg);
    2018        final int nargs = argtypes.length;
    2019
    2020        for (int i=nargs-1; i>=0; i--) {
    2021            final Type fromStack = stack().peek( (nargs-1) - i );    // 0 to nargs-1
    2022            Type fromDesc = argtypes[i];
    2023            if (fromDesc == Type.BOOLEAN ||
    2024                    fromDesc == Type.BYTE ||
    2025                    fromDesc == Type.CHAR ||
    2026                    fromDesc == Type.SHORT) {
    2027                fromDesc = Type.INT;
    2028            }
    2029            if (! fromStack.equals(fromDesc)) {
    2030                if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType) {
    2031                    final ReferenceType rFromStack = (ReferenceType) fromStack;
    2032                    final ReferenceType rFromDesc = (ReferenceType) fromDesc;
    2033                    // TODO: This check can possibly only be done using Staerk-et-al's "set of object types"
    2034                    // instead of a "wider cast object type" created during verification.
    2035                    if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ) {
    2036                        constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+
    2037                            "' on the stack (which is not assignment compatible).");
    2038                    }
    2039                    referenceTypeIsInitialized(o, rFromStack);
    2040                }
    2041                else{
    2042                    constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
    2043                }
    2044            }
    2045        }
    2046        } catch (final ClassNotFoundException e) {
    2047        // FIXME: maybe not the best way to handle this
    2048        throw new AssertionViolatedException("Missing class: " + e, e);
    2049        }
    2050    }
    2051
    2052    /**
    2053     * Ensures the specific preconditions of the said instruction.
    2054     */
    2055    @Override
    2056    public void visitINVOKEVIRTUAL(final INVOKEVIRTUAL o) {
    2057        try {
    2058        // the o.getClassType(cpg) type has passed pass 2; see visitLoadClass(o).
    2059
    2060        final Type t = o.getType(cpg);
    2061        if (t instanceof ObjectType) {
    2062            final String name = ((ObjectType)t).getClassName();
    2063            final Verifier v = VerifierFactory.getVerifier( name );
    2064            final VerificationResult vr = v.doPass2();
    2065            if (vr.getStatus() != VerificationResult.VERIFIED_OK) {
    2066                constraintViolated(o, "Class '"+name+"' is referenced, but cannot be loaded and resolved: '"+vr+"'.");
    2067            }
    2068        }
    2069
    2070
    2071        final Type[] argtypes = o.getArgumentTypes(cpg);
    2072        final int nargs = argtypes.length;
    2073
    2074        for (int i=nargs-1; i>=0; i--) {
    2075            final Type fromStack = stack().peek( (nargs-1) - i );    // 0 to nargs-1
    2076            Type fromDesc = argtypes[i];
    2077            if (fromDesc == Type.BOOLEAN ||
    2078                    fromDesc == Type.BYTE ||
    2079                    fromDesc == Type.CHAR ||
    2080                    fromDesc == Type.SHORT) {
    2081                fromDesc = Type.INT;
    2082            }
    2083            if (! fromStack.equals(fromDesc)) {
    2084                if (fromStack instanceof ReferenceType && fromDesc instanceof ReferenceType) {
    2085                    final ReferenceType rFromStack = (ReferenceType) fromStack;
    2086                    final ReferenceType rFromDesc = (ReferenceType) fromDesc;
    2087                    // TODO: This can possibly only be checked when using Staerk-et-al's "set of object types" instead
    2088                    // of a single "wider cast object type" created during verification.
    2089                    if ( ! rFromStack.isAssignmentCompatibleWith(rFromDesc) ) {
    2090                        constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+
    2091                            "' on the stack (which is not assignment compatible).");
    2092                    }
    2093                    referenceTypeIsInitialized(o, rFromStack);
    2094                }
    2095                else{
    2096                    constraintViolated(o, "Expecting a '"+fromDesc+"' but found a '"+fromStack+"' on the stack.");
    2097                }
    2098            }
    2099        }
    2100
    2101        Type objref = stack().peek(nargs);
    2102        if (objref == Type.NULL) {
    2103            return;
    2104        }
    2105        if (! (objref instanceof ReferenceType) ) {
    2106            constraintViolated(o, "Expecting a reference type as 'objectref' on the stack, not a '"+objref+"'.");
    2107        }
    2108        referenceTypeIsInitialized(o, (ReferenceType) objref);
    2109        if (!(objref instanceof ObjectType)) {
    2110            if (!(objref instanceof ArrayType)) { // could be a ReturnaddressType
    2111                constraintViolated(o, "Expecting an ObjectType as 'objectref' on the stack, not a '"+objref+"'.");
    2112            }
    2113            else{
    2114                objref = GENERIC_ARRAY;
    2115            }
    2116        }
    2117
    2118        final String objref_classname = ((ObjectType) objref).getClassName();
    2119
    2120        final String theClass = o.getClassName(cpg);
    2121
    2122        if ( ! Repository.instanceOf(objref_classname, theClass) ) {
    2123            constraintViolated(o, "The 'objref' item '"+objref+"' does not implement '"+theClass+"' as expected.");
    2124        }
    2125        } catch (final ClassNotFoundException e) {
    2126        // FIXME: maybe not the best way to handle this
    2127        throw new AssertionViolatedException("Missing class: " + e, e);
    2128        }
    2129    }
    2130
    2131    /**
    2132     * Ensures the specific preconditions of the said instruction.
    2133     */
    2134    @Override
    2135    public void visitIOR(final IOR o) {
    2136        if (stack().peek() != Type.INT) {
    2137            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2138        }
    2139        if (stack().peek(1) != Type.INT) {
    2140            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    2141        }
    2142    }
    2143
    2144    /**
    2145     * Ensures the specific preconditions of the said instruction.
    2146     */
    2147    @Override
    2148    public void visitIREM(final IREM o) {
    2149        if (stack().peek() != Type.INT) {
    2150            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2151        }
    2152        if (stack().peek(1) != Type.INT) {
    2153            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    2154        }
    2155    }
    2156
    2157    /**
    2158     * Ensures the specific preconditions of the said instruction.
    2159     */
    2160    @Override
    2161    public void visitIRETURN(final IRETURN o) {
    2162        if (stack().peek() != Type.INT) {
    2163            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2164        }
    2165    }
    2166
    2167    /**
    2168     * Ensures the specific preconditions of the said instruction.
    2169     */
    2170    @Override
    2171    public void visitISHL(final ISHL o) {
    2172        if (stack().peek() != Type.INT) {
    2173            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2174        }
    2175        if (stack().peek(1) != Type.INT) {
    2176            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    2177        }
    2178    }
    2179
    2180    /**
    2181     * Ensures the specific preconditions of the said instruction.
    2182     */
    2183    @Override
    2184    public void visitISHR(final ISHR o) {
    2185        if (stack().peek() != Type.INT) {
    2186            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2187        }
    2188        if (stack().peek(1) != Type.INT) {
    2189            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    2190        }
    2191    }
    2192
    2193    /**
    2194     * Ensures the specific preconditions of the said instruction.
    2195     */
    2196    @Override
    2197    public void visitISTORE(final ISTORE o) {
    2198        //visitStoreInstruction(StoreInstruction) is called before.
    2199
    2200        // Nothing else needs to be done here.
    2201    }
    2202
    2203    /**
    2204     * Ensures the specific preconditions of the said instruction.
    2205     */
    2206    @Override
    2207    public void visitISUB(final ISUB o) {
    2208        if (stack().peek() != Type.INT) {
    2209            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2210        }
    2211        if (stack().peek(1) != Type.INT) {
    2212            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    2213        }
    2214    }
    2215
    2216    /**
    2217     * Ensures the specific preconditions of the said instruction.
    2218     */
    2219    @Override
    2220    public void visitIUSHR(final IUSHR o) {
    2221        if (stack().peek() != Type.INT) {
    2222            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2223        }
    2224        if (stack().peek(1) != Type.INT) {
    2225            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    2226        }
    2227    }
    2228
    2229    /**
    2230     * Ensures the specific preconditions of the said instruction.
    2231     */
    2232    @Override
    2233    public void visitIXOR(final IXOR o) {
    2234        if (stack().peek() != Type.INT) {
    2235            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2236        }
    2237        if (stack().peek(1) != Type.INT) {
    2238            constraintViolated(o, "The value at the stack next-to-top is not of type 'int', but of type '"+stack().peek(1)+"'.");
    2239        }
    2240    }
    2241
    2242    /**
    2243     * Ensures the specific preconditions of the said instruction.
    2244     */
    2245    @Override
    2246    public void visitJSR(final JSR o) {
    2247        // nothing to do here.
    2248    }
    2249
    2250    /**
    2251     * Ensures the specific preconditions of the said instruction.
    2252     */
    2253    @Override
    2254    public void visitJSR_W(final JSR_W o) {
    2255        // nothing to do here.
    2256    }
    2257
    2258    /**
    2259     * Ensures the specific preconditions of the said instruction.
    2260     */
    2261    @Override
    2262    public void visitL2D(final L2D o) {
    2263        if (stack().peek() != Type.LONG) {
    2264            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2265        }
    2266    }
    2267
    2268    /**
    2269     * Ensures the specific preconditions of the said instruction.
    2270     */
    2271    @Override
    2272    public void visitL2F(final L2F o) {
    2273        if (stack().peek() != Type.LONG) {
    2274            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2275        }
    2276    }
    2277
    2278    /**
    2279     * Ensures the specific preconditions of the said instruction.
    2280     */
    2281    @Override
    2282    public void visitL2I(final L2I o) {
    2283        if (stack().peek() != Type.LONG) {
    2284            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2285        }
    2286    }
    2287
    2288    /**
    2289     * Ensures the specific preconditions of the said instruction.
    2290     */
    2291    @Override
    2292    public void visitLADD(final LADD o) {
    2293        if (stack().peek() != Type.LONG) {
    2294            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2295        }
    2296        if (stack().peek(1) != Type.LONG) {
    2297            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2298        }
    2299    }
    2300
    2301    /**
    2302     * Ensures the specific preconditions of the said instruction.
    2303     */
    2304    @Override
    2305    public void visitLALOAD(final LALOAD o) {
    2306        indexOfInt(o, stack().peek());
    2307        if (stack().peek(1) == Type.NULL) {
    2308            return;
    2309        }
    2310        if (! (stack().peek(1) instanceof ArrayType)) {
    2311            constraintViolated(o, "Stack next-to-top must be of type long[] but is '"+stack().peek(1)+"'.");
    2312        }
    2313        final Type t = ((ArrayType) (stack().peek(1))).getBasicType();
    2314        if (t != Type.LONG) {
    2315            constraintViolated(o, "Stack next-to-top must be of type long[] but is '"+stack().peek(1)+"'.");
    2316        }
    2317    }
    2318
    2319    /**
    2320     * Ensures the specific preconditions of the said instruction.
    2321     */
    2322    @Override
    2323    public void visitLAND(final LAND o) {
    2324        if (stack().peek() != Type.LONG) {
    2325            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2326        }
    2327        if (stack().peek(1) != Type.LONG) {
    2328            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2329        }
    2330    }
    2331
    2332    /**
    2333     * Ensures the specific preconditions of the said instruction.
    2334     */
    2335    @Override
    2336    public void visitLASTORE(final LASTORE o) {
    2337        if (stack().peek() != Type.LONG) {
    2338            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2339        }
    2340        indexOfInt(o, stack().peek(1));
    2341        if (stack().peek(2) == Type.NULL) {
    2342            return;
    2343        }
    2344        if (! (stack().peek(2) instanceof ArrayType)) {
    2345            constraintViolated(o, "Stack next-to-next-to-top must be of type long[] but is '"+stack().peek(2)+"'.");
    2346        }
    2347        final Type t = ((ArrayType) (stack().peek(2))).getBasicType();
    2348        if (t != Type.LONG) {
    2349            constraintViolated(o, "Stack next-to-next-to-top must be of type long[] but is '"+stack().peek(2)+"'.");
    2350        }
    2351    }
    2352
    2353    /**
    2354     * Ensures the specific preconditions of the said instruction.
    2355     */
    2356    @Override
    2357    public void visitLCMP(final LCMP o) {
    2358        if (stack().peek() != Type.LONG) {
    2359            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2360        }
    2361        if (stack().peek(1) != Type.LONG) {
    2362            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2363        }
    2364    }
    2365
    2366    /**
    2367     * Ensures the specific preconditions of the said instruction.
    2368     */
    2369    @Override
    2370    public void visitLCONST(final LCONST o) {
    2371        // Nothing to do here.
    2372    }
    2373
    2374    /**
    2375     * Ensures the specific preconditions of the said instruction.
    2376     */
    2377    @Override
    2378    public void visitLDC(final LDC o) {
    2379        // visitCPInstruction is called first.
    2380
    2381        final Constant c = cpg.getConstant(o.getIndex());
    2382        if     (!    (    ( c instanceof ConstantInteger) ||
    2383                    ( c instanceof ConstantFloat    )    ||
    2384                    ( c instanceof ConstantString    )    ||
    2385                    ( c instanceof ConstantClass    ) )    ) {
    2386            constraintViolated(o,
    2387                "Referenced constant should be a CONSTANT_Integer, a CONSTANT_Float, a CONSTANT_String or a CONSTANT_Class, but is '"+
    2388                 c + "'.");
    2389        }
    2390    }
    2391
    2392    /**
    2393     * Ensures the specific preconditions of the said instruction.
    2394     */
    2395    public void visitLDC_W(final LDC_W o) {
    2396        // visitCPInstruction is called first.
    2397
    2398        final Constant c = cpg.getConstant(o.getIndex());
    2399        if     (!    (    ( c instanceof ConstantInteger) ||
    2400                    ( c instanceof ConstantFloat    )    ||
    2401                    ( c instanceof ConstantString    )    ||
    2402                    ( c instanceof ConstantClass    ) )    ) {
    2403            constraintViolated(o,
    2404                "Referenced constant should be a CONSTANT_Integer, a CONSTANT_Float, a CONSTANT_String or a CONSTANT_Class, but is '"+
    2405                 c + "'.");
    2406        }
    2407    }
    2408
    2409    /**
    2410     * Ensures the specific preconditions of the said instruction.
    2411     */
    2412    @Override
    2413    public void visitLDC2_W(final LDC2_W o) {
    2414        // visitCPInstruction is called first.
    2415
    2416        final Constant c = cpg.getConstant(o.getIndex());
    2417        if     (!    (    ( c instanceof ConstantLong) ||
    2418                            ( c instanceof ConstantDouble )    )    ) {
    2419            constraintViolated(o,
    2420                    "Referenced constant should be a CONSTANT_Integer, a CONSTANT_Float or a CONSTANT_String, but is '"+c+"'.");
    2421        }
    2422    }
    2423
    2424    /**
    2425     * Ensures the specific preconditions of the said instruction.
    2426     */
    2427    @Override
    2428    public void visitLDIV(final LDIV o) {
    2429        if (stack().peek() != Type.LONG) {
    2430            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2431        }
    2432        if (stack().peek(1) != Type.LONG) {
    2433            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2434        }
    2435    }
    2436
    2437    /**
    2438     * Ensures the specific preconditions of the said instruction.
    2439     */
    2440    @Override
    2441    public void visitLLOAD(final LLOAD o) {
    2442        //visitLoadInstruction(LoadInstruction) is called before.
    2443
    2444        // Nothing else needs to be done here.
    2445    }
    2446
    2447    /**
    2448     * Ensures the specific preconditions of the said instruction.
    2449     */
    2450    @Override
    2451    public void visitLMUL(final LMUL o) {
    2452        if (stack().peek() != Type.LONG) {
    2453            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2454        }
    2455        if (stack().peek(1) != Type.LONG) {
    2456            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2457        }
    2458    }
    2459
    2460    /**
    2461     * Ensures the specific preconditions of the said instruction.
    2462     */
    2463    @Override
    2464    public void visitLNEG(final LNEG o) {
    2465        if (stack().peek() != Type.LONG) {
    2466            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2467        }
    2468    }
    2469
    2470    /**
    2471     * Ensures the specific preconditions of the said instruction.
    2472     */
    2473    @Override
    2474    public void visitLOOKUPSWITCH(final LOOKUPSWITCH o) {
    2475        if (stack().peek() != Type.INT) {
    2476            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2477        }
    2478        // See also pass 3a.
    2479    }
    2480
    2481    /**
    2482     * Ensures the specific preconditions of the said instruction.
    2483     */
    2484    @Override
    2485    public void visitLOR(final LOR o) {
    2486        if (stack().peek() != Type.LONG) {
    2487            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2488        }
    2489        if (stack().peek(1) != Type.LONG) {
    2490            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2491        }
    2492    }
    2493
    2494    /**
    2495     * Ensures the specific preconditions of the said instruction.
    2496     */
    2497    @Override
    2498    public void visitLREM(final LREM o) {
    2499        if (stack().peek() != Type.LONG) {
    2500            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2501        }
    2502        if (stack().peek(1) != Type.LONG) {
    2503            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2504        }
    2505    }
    2506
    2507    /**
    2508     * Ensures the specific preconditions of the said instruction.
    2509     */
    2510    @Override
    2511    public void visitLRETURN(final LRETURN o) {
    2512        if (stack().peek() != Type.LONG) {
    2513            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2514        }
    2515    }
    2516
    2517    /**
    2518     * Ensures the specific preconditions of the said instruction.
    2519     */
    2520    @Override
    2521    public void visitLSHL(final LSHL o) {
    2522        if (stack().peek() != Type.INT) {
    2523            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2524        }
    2525        if (stack().peek(1) != Type.LONG) {
    2526            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2527        }
    2528    }
    2529
    2530    /**
    2531     * Ensures the specific preconditions of the said instruction.
    2532     */
    2533    @Override
    2534    public void visitLSHR(final LSHR o) {
    2535        if (stack().peek() != Type.INT) {
    2536            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2537        }
    2538        if (stack().peek(1) != Type.LONG) {
    2539            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2540        }
    2541    }
    2542
    2543    /**
    2544     * Ensures the specific preconditions of the said instruction.
    2545     */
    2546    @Override
    2547    public void visitLSTORE(final LSTORE o) {
    2548        //visitStoreInstruction(StoreInstruction) is called before.
    2549
    2550        // Nothing else needs to be done here.
    2551    }
    2552
    2553    /**
    2554     * Ensures the specific preconditions of the said instruction.
    2555     */
    2556    @Override
    2557    public void visitLSUB(final LSUB o) {
    2558        if (stack().peek() != Type.LONG) {
    2559            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2560        }
    2561        if (stack().peek(1) != Type.LONG) {
    2562            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2563        }
    2564    }
    2565
    2566    /**
    2567     * Ensures the specific preconditions of the said instruction.
    2568     */
    2569    @Override
    2570    public void visitLUSHR(final LUSHR o) {
    2571        if (stack().peek() != Type.INT) {
    2572            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2573        }
    2574        if (stack().peek(1) != Type.LONG) {
    2575            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2576        }
    2577    }
    2578
    2579    /**
    2580     * Ensures the specific preconditions of the said instruction.
    2581     */
    2582    @Override
    2583    public void visitLXOR(final LXOR o) {
    2584        if (stack().peek() != Type.LONG) {
    2585            constraintViolated(o, "The value at the stack top is not of type 'long', but of type '"+stack().peek()+"'.");
    2586        }
    2587        if (stack().peek(1) != Type.LONG) {
    2588            constraintViolated(o, "The value at the stack next-to-top is not of type 'long', but of type '"+stack().peek(1)+"'.");
    2589        }
    2590    }
    2591
    2592    /**
    2593     * Ensures the specific preconditions of the said instruction.
    2594     */
    2595    @Override
    2596    public void visitMONITORENTER(final MONITORENTER o) {
    2597        if (! ((stack().peek()) instanceof ReferenceType)) {
    2598            constraintViolated(o, "The stack top should be of a ReferenceType, but is '"+stack().peek()+"'.");
    2599        }
    2600        //referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
    2601    }
    2602
    2603    /**
    2604     * Ensures the specific preconditions of the said instruction.
    2605     */
    2606    @Override
    2607    public void visitMONITOREXIT(final MONITOREXIT o) {
    2608        if (! ((stack().peek()) instanceof ReferenceType)) {
    2609            constraintViolated(o, "The stack top should be of a ReferenceType, but is '"+stack().peek()+"'.");
    2610        }
    2611        //referenceTypeIsInitialized(o, (ReferenceType) (stack().peek()) );
    2612    }
    2613
    2614    /**
    2615     * Ensures the specific preconditions of the said instruction.
    2616     */
    2617    @Override
    2618    public void visitMULTIANEWARRAY(final MULTIANEWARRAY o) {
    2619        final int dimensions = o.getDimensions();
    2620        // Dimensions argument is okay: see Pass 3a.
    2621        for (int i=0; i<dimensions; i++) {
    2622            if (stack().peek(i) != Type.INT) {
    2623                constraintViolated(o, "The '"+dimensions+"' upper stack types should be 'int' but aren't.");
    2624            }
    2625        }
    2626        // The runtime constant pool item at that index must be a symbolic reference to a class,
    2627        // array, or interface type. See Pass 3a.
    2628    }
    2629
    2630    /**
    2631     * Ensures the specific preconditions of the said instruction.
    2632     */
    2633    @Override
    2634    public void visitNEW(final NEW o) {
    2635        //visitCPInstruction(CPInstruction) has been called before.
    2636        //visitLoadClass(LoadClass) has been called before.
    2637
    2638        final Type t = o.getType(cpg);
    2639        if (! (t instanceof ReferenceType)) {
    2640            throw new AssertionViolatedException("NEW.getType() returning a non-reference type?!");
    2641        }
    2642        if (! (t instanceof ObjectType)) {
    2643            constraintViolated(o, "Expecting a class type (ObjectType) to work on. Found: '"+t+"'.");
    2644        }
    2645        final ObjectType obj = (ObjectType) t;
    2646
    2647        //e.g.: Don't instantiate interfaces
    2648        try {
    2649            if (! obj.referencesClassExact()) {
    2650                constraintViolated(o, "Expecting a class type (ObjectType) to work on. Found: '"+obj+"'.");
    2651            }
    2652        } catch (final ClassNotFoundException e) {
    2653            constraintViolated(o, "Expecting a class type (ObjectType) to work on. Found: '"+obj+"'." + " which threw " + e);
    2654        }
    2655    }
    2656
    2657    /**
    2658     * Ensures the specific preconditions of the said instruction.
    2659     */
    2660    @Override
    2661    public void visitNEWARRAY(final NEWARRAY o) {
    2662        if (stack().peek() != Type.INT) {
    2663            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2664        }
    2665    }
    2666
    2667    /**
    2668     * Ensures the specific preconditions of the said instruction.
    2669     */
    2670    @Override
    2671    public void visitNOP(final NOP o) {
    2672        // nothing is to be done here.
    2673    }
    2674
    2675    /**
    2676     * Ensures the specific preconditions of the said instruction.
    2677     */
    2678    @Override
    2679    public void visitPOP(final POP o) {
    2680        if (stack().peek().getSize() != 1) {
    2681            constraintViolated(o,
    2682                "Stack top size should be 1 but stack top is '"+stack().peek()+"' of size '"+stack().peek().getSize()+"'.");
    2683        }
    2684    }
    2685
    2686    /**
    2687     * Ensures the specific preconditions of the said instruction.
    2688     */
    2689    @Override
    2690    public void visitPOP2(final POP2 o) {
    2691        if (stack().peek().getSize() != 2) {
    2692            constraintViolated(o,
    2693                "Stack top size should be 2 but stack top is '"+stack().peek()+"' of size '"+stack().peek().getSize()+"'.");
    2694        }
    2695    }
    2696
    2697    /**
    2698     * Ensures the specific preconditions of the said instruction.
    2699     */
    2700    @Override
    2701    public void visitPUTFIELD(final PUTFIELD o) {
    2702        try {
    2703
    2704        final Type objectref = stack().peek(1);
    2705        if (! ( (objectref instanceof ObjectType) || (objectref == Type.NULL) ) ) {
    2706            constraintViolated(o,
    2707                "Stack next-to-top should be an object reference that's not an array reference, but is '"+objectref+"'.");
    2708        }
    2709
    2710        final String field_name = o.getFieldName(cpg);
    2711
    2712        final JavaClass jc = Repository.lookupClass(getObjectType(o).getClassName());
    2713        final Field[] fields = jc.getFields();
    2714        Field f = null;
    2715        for (final Field field : fields) {
    2716            if (field.getName().equals(field_name)) {
    2717                  final Type f_type = Type.getType(field.getSignature());
    2718                  final Type o_type = o.getType(cpg);
    2719                    /* TODO: Check if assignment compatibility is sufficient.
    2720                   * What does Sun do?
    2721                   */
    2722                  if (f_type.equals(o_type)) {
    2723                        f = field;
    2724                        break;
    2725                    }
    2726            }
    2727        }
    2728        if (f == null) {
    2729            throw new AssertionViolatedException("Field '" + field_name + "' not found in " + jc.getClassName());
    2730        }
    2731
    2732        final Type value = stack().peek();
    2733        final Type t = Type.getType(f.getSignature());
    2734        Type shouldbe = t;
    2735        if (shouldbe == Type.BOOLEAN ||
    2736                shouldbe == Type.BYTE ||
    2737                shouldbe == Type.CHAR ||
    2738                shouldbe == Type.SHORT) {
    2739            shouldbe = Type.INT;
    2740        }
    2741        if (t instanceof ReferenceType) {
    2742            ReferenceType rvalue = null;
    2743            if (value instanceof ReferenceType) {
    2744                rvalue = (ReferenceType) value;
    2745                referenceTypeIsInitialized(o, rvalue);
    2746            }
    2747            else{
    2748                constraintViolated(o, "The stack top type '"+value+"' is not of a reference type as expected.");
    2749            }
    2750            // TODO: This can possibly only be checked using Staerk-et-al's "set-of-object types", not
    2751            // using "wider cast object types" created during verification.
    2752            // Comment it out if you encounter problems. See also the analogon at visitPUTSTATIC.
    2753            if (!(rvalue.isAssignmentCompatibleWith(shouldbe))) {
    2754                constraintViolated(o, "The stack top type '"+value+"' is not assignment compatible with '"+shouldbe+"'.");
    2755            }
    2756        }
    2757        else{
    2758            if (shouldbe != value) {
    2759                constraintViolated(o, "The stack top type '"+value+"' is not of type '"+shouldbe+"' as expected.");
    2760            }
    2761        }
    2762
    2763        if (f.isProtected()) {
    2764            final ObjectType classtype = getObjectType(o);
    2765            final ObjectType curr = ObjectType.getInstance(mg.getClassName());
    2766
    2767            if (    classtype.equals(curr) ||
    2768                        curr.subclassOf(classtype)    ) {
    2769                final Type tp = stack().peek(1);
    2770                if (tp == Type.NULL) {
    2771                    return;
    2772                }
    2773                if (! (tp instanceof ObjectType) ) {
    2774                    constraintViolated(o, "The 'objectref' must refer to an object that's not an array. Found instead: '"+tp+"'.");
    2775                }
    2776                final ObjectType objreftype = (ObjectType) tp;
    2777                if (! ( objreftype.equals(curr) ||
    2778                            objreftype.subclassOf(curr) ) ) {
    2779                    constraintViolated(o,
    2780                        "The referenced field has the ACC_PROTECTED modifier, and it's a member of the current class or"+
    2781                        " a superclass of the current class. However, the referenced object type '"+stack().peek()+
    2782                        "' is not the current class or a subclass of the current class.");
    2783                }
    2784            }
    2785        }
    2786
    2787        // TODO: Could go into Pass 3a.
    2788        if (f.isStatic()) {
    2789            constraintViolated(o, "Referenced field '"+f+"' is static which it shouldn't be.");
    2790        }
    2791
    2792        } catch (final ClassNotFoundException e) {
    2793        // FIXME: maybe not the best way to handle this
    2794        throw new AssertionViolatedException("Missing class: " + e, e);
    2795        }
    2796    }
    2797
    2798    /**
    2799     * Ensures the specific preconditions of the said instruction.
    2800     */
    2801    @Override
    2802    public void visitPUTSTATIC(final PUTSTATIC o) {
    2803        try {
    2804        final String field_name = o.getFieldName(cpg);
    2805        final JavaClass jc = Repository.lookupClass(getObjectType(o).getClassName());
    2806        final Field[] fields = jc.getFields();
    2807        Field f = null;
    2808        for (final Field field : fields) {
    2809            if (field.getName().equals(field_name)) {
    2810                    final Type f_type = Type.getType(field.getSignature());
    2811                  final Type o_type = o.getType(cpg);
    2812                    /* TODO: Check if assignment compatibility is sufficient.
    2813                   * What does Sun do?
    2814                   */
    2815                  if (f_type.equals(o_type)) {
    2816                        f = field;
    2817                        break;
    2818                    }
    2819            }
    2820        }
    2821        if (f == null) {
    2822            throw new AssertionViolatedException("Field '" + field_name + "' not found in " + jc.getClassName());
    2823        }
    2824        final Type value = stack().peek();
    2825        final Type t = Type.getType(f.getSignature());
    2826        Type shouldbe = t;
    2827        if (shouldbe == Type.BOOLEAN ||
    2828                shouldbe == Type.BYTE ||
    2829                shouldbe == Type.CHAR ||
    2830                shouldbe == Type.SHORT) {
    2831            shouldbe = Type.INT;
    2832        }
    2833        if (t instanceof ReferenceType) {
    2834            ReferenceType rvalue = null;
    2835            if (value instanceof ReferenceType) {
    2836                rvalue = (ReferenceType) value;
    2837                referenceTypeIsInitialized(o, rvalue);
    2838            }
    2839            else{
    2840                constraintViolated(o, "The stack top type '"+value+"' is not of a reference type as expected.");
    2841            }
    2842            // TODO: This can possibly only be checked using Staerk-et-al's "set-of-object types", not
    2843            // using "wider cast object types" created during verification.
    2844            // Comment it out if you encounter problems. See also the analogon at visitPUTFIELD.
    2845            if (!(rvalue.isAssignmentCompatibleWith(shouldbe))) {
    2846                constraintViolated(o, "The stack top type '"+value+"' is not assignment compatible with '"+shouldbe+"'.");
    2847            }
    2848        }
    2849        else{
    2850            if (shouldbe != value) {
    2851                constraintViolated(o, "The stack top type '"+value+"' is not of type '"+shouldbe+"' as expected.");
    2852            }
    2853        }
    2854        // TODO: Interface fields may be assigned to only once. (Hard to implement in
    2855        //       JustIce's execution model). This may only happen in <clinit>, see Pass 3a.
    2856
    2857        } catch (final ClassNotFoundException e) {
    2858        // FIXME: maybe not the best way to handle this
    2859        throw new AssertionViolatedException("Missing class: " + e, e);
    2860        }
    2861    }
    2862
    2863    /**
    2864     * Ensures the specific preconditions of the said instruction.
    2865     */
    2866    @Override
    2867    public void visitRET(final RET o) {
    2868        if (! (locals().get(o.getIndex()) instanceof ReturnaddressType)) {
    2869            constraintViolated(o, "Expecting a ReturnaddressType in local variable "+o.getIndex()+".");
    2870        }
    2871        if (locals().get(o.getIndex()) == ReturnaddressType.NO_TARGET) {
    2872            throw new AssertionViolatedException("RET expecting a target!");
    2873        }
    2874        // Other constraints such as non-allowed overlapping subroutines are enforced
    2875        // while building the Subroutines data structure.
    2876    }
    2877
    2878    /**
    2879     * Ensures the specific preconditions of the said instruction.
    2880     */
    2881    @Override
    2882    public void visitRETURN(final RETURN o) {
    2883        if (mg.getName().equals(Const.CONSTRUCTOR_NAME)) {// If we leave an <init> method
    2884            if ((Frame.getThis() != null) && (!(mg.getClassName().equals(Type.OBJECT.getClassName()))) ) {
    2885                constraintViolated(o, "Leaving a constructor that itself did not call a constructor.");
    2886            }
    2887        }
    2888    }
    2889
    2890    /**
    2891     * Ensures the specific preconditions of the said instruction.
    2892     */
    2893    @Override
    2894    public void visitSALOAD(final SALOAD o) {
    2895        indexOfInt(o, stack().peek());
    2896        if (stack().peek(1) == Type.NULL) {
    2897            return;
    2898        }
    2899        if (! (stack().peek(1) instanceof ArrayType)) {
    2900            constraintViolated(o, "Stack next-to-top must be of type short[] but is '"+stack().peek(1)+"'.");
    2901        }
    2902        final Type t = ((ArrayType) (stack().peek(1))).getBasicType();
    2903        if (t != Type.SHORT) {
    2904            constraintViolated(o, "Stack next-to-top must be of type short[] but is '"+stack().peek(1)+"'.");
    2905        }
    2906    }
    2907
    2908    /**
    2909     * Ensures the specific preconditions of the said instruction.
    2910     */
    2911    @Override
    2912    public void visitSASTORE(final SASTORE o) {
    2913        if (stack().peek() != Type.INT) {
    2914            constraintViolated(o, "The value at the stack top is not of type 'int', but of type '"+stack().peek()+"'.");
    2915        }
    2916        indexOfInt(o, stack().peek(1));
    2917        if (stack().peek(2) == Type.NULL) {
    2918            return;
    2919        }
    2920        if (! (stack().peek(2) instanceof ArrayType)) {
    2921            constraintViolated(o, "Stack next-to-next-to-top must be of type short[] but is '"+stack().peek(2)+"'.");
    2922        }
    2923        final Type t = ((ArrayType) (stack().peek(2))).getBasicType();
    2924        if (t != Type.SHORT) {
    2925            constraintViolated(o, "Stack next-to-next-to-top must be of type short[] but is '"+stack().peek(2)+"'.");
    2926        }
    2927    }
    2928
    2929    /**
    2930     * Ensures the specific preconditions of the said instruction.
    2931     */
    2932    @Override
    2933    public void visitSIPUSH(final SIPUSH o) {
    2934        // nothing to do here. Generic visitXXX() methods did the trick before.
    2935    }
    2936
    2937    /**
    2938     * Ensures the specific preconditions of the said instruction.
    2939     */
    2940    @Override
    2941    public void visitSWAP(final SWAP o) {
    2942        if (stack().peek().getSize() != 1) {
    2943            constraintViolated(o, "The value at the stack top is not of size '1', but of size '"+stack().peek().getSize()+"'.");
    2944        }
    2945        if (stack().peek(1).getSize() != 1) {
    2946            constraintViolated(o,
    2947                "The value at the stack next-to-top is not of size '1', but of size '"+stack().peek(1).getSize()+"'.");
    2948        }
    2949    }
    2950
    2951    /**
    2952     * Ensures the specific preconditions of the said instruction.
    2953     */
    2954    @Override
    2955    public void visitTABLESWITCH(final TABLESWITCH o) {
    2956        indexOfInt(o, stack().peek());
    2957        // See Pass 3a.
    2958    }
    2959
    2960}
    2961