    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.generic.ReferenceType;
    022import org.apache.bcel.generic.Type;
    023import org.apache.bcel.verifier.exc.AssertionViolatedException;
    024import org.apache.bcel.verifier.exc.StructuralCodeConstraintException;
    025
    026/**
    027 * This class implements an array of local variables used for symbolic JVM
    028 * simulation.
    029 */
    030public class LocalVariables implements Cloneable {
    031
    032    /** The Type[] containing the local variable slots. */
    033    private final Type[] locals;
    034
    035    /**
    036     * Creates a new LocalVariables object.
    037     *
    038     * @param localVariableCount local variable count.
    039     */
    040    public LocalVariables(final int localVariableCount) {
    041        locals = new Type[localVariableCount];
    042        for (int i=0; i<localVariableCount; i++) {
    043            locals[i] = Type.UNKNOWN;
    044        }
    045    }
    046
    047    /**
    048     * Returns a deep copy of this object; i.e. the clone
    049     * operates on a new local variable array.
    050     * However, the Type objects in the array are shared.
    051     */
    052    @Override
    053    public Object clone() {
    054        final LocalVariables lvs = new LocalVariables(locals.length);
    055        for (int i=0; i<locals.length; i++) {
    056            lvs.locals[i] = this.locals[i];
    057        }
    058        return lvs;
    059    }
    060
    061    /**
    062     * Returns the type of the local variable slot index.
    063     *
    064     * @param slotIndex Slot to look up.
    065     * @return the type of the local variable slot index.
    066     */
    067    public Type get(final int slotIndex) {
    068        return locals[slotIndex];
    069    }
    070
    071    /**
    072     * Returns a (correctly typed) clone of this object.
    073     * This is equivalent to ((LocalVariables) this.clone()).
    074     *
    075     * @return a (correctly typed) clone of this object.
    076     */
    077    public LocalVariables getClone() {
    078        return (LocalVariables) this.clone();
    079    }
    080
    081    /**
    082     * Returns the number of local variable slots.
    083     *
    084     * @return the number of local variable slots.
    085     */
    086    public int maxLocals() {
    087        return locals.length;
    088    }
    089
    090    /**
    091     * Sets a new Type for the given local variable slot.
    092     *
    093     * @param slotIndex Target slot index.
    094     * @param type Type to save at the given slot index.
    095     */
    096    public void set(final int slotIndex, final Type type) { // TODO could be package-protected?
    097        if (type == Type.BYTE || type == Type.SHORT || type == Type.BOOLEAN || type == Type.CHAR) {
    098            throw new AssertionViolatedException("LocalVariables do not know about '"+type+"'. Use Type.INT instead.");
    099        }
    100        locals[slotIndex] = type;
    101    }
    102
    103    /** @return a hash code value for the object.
    104     */
    105    @Override
    106    public int hashCode() { return locals.length; }
    107
    108    /*
    109     * Fulfills the general contract of Object.equals().
    110     */
    111    @Override
    112    public boolean equals(final Object o) {
    113        if (!(o instanceof LocalVariables)) {
    114            return false;
    115        }
    116        final LocalVariables lv = (LocalVariables) o;
    117        if (this.locals.length != lv.locals.length) {
    118            return false;
    119        }
    120        for (int i=0; i<this.locals.length; i++) {
    121            if (!this.locals[i].equals(lv.locals[i])) {
    122                //System.out.println(this.locals[i]+" is not "+lv.locals[i]);
    123                return false;
    124            }
    125        }
    126        return true;
    127    }
    128
    129    /**
    130     * Merges two local variables sets as described in the Java Virtual Machine Specification,
    131     * Second Edition, section 4.9.2, page 146.
    132     *
    133     * @param localVariable other local variable.
    134     */
    135    public void merge(final LocalVariables localVariable) {
    136
    137        if (this.locals.length != localVariable.locals.length) {
    138            throw new AssertionViolatedException("Merging LocalVariables of different size?!? From different methods or what?!?");
    139        }
    140
    141        for (int i=0; i<locals.length; i++) {
    142            merge(localVariable, i);
    143        }
    144    }
    145
    146    /**
    147     * Merges a single local variable.
    148     *
    149     * @see #merge(LocalVariables)
    150     */
    151    private void merge(final LocalVariables lv, final int i) {
    152        try {
    153
    154        // We won't accept an unitialized object if we know it was initialized;
    155        // compare vmspec2, 4.9.4, last paragraph.
    156        if ( (!(locals[i] instanceof UninitializedObjectType)) && (lv.locals[i] instanceof UninitializedObjectType) ) {
    157            throw new StructuralCodeConstraintException(
    158                "Backwards branch with an uninitialized object in the local variables detected.");
    159        }
    160        // Even harder, what about _different_ uninitialized object types?!
    161        if ( (!(locals[i].equals(lv.locals[i]))) && (locals[i] instanceof UninitializedObjectType) &&
    162                (lv.locals[i] instanceof UninitializedObjectType) ) {
    163            throw new StructuralCodeConstraintException(
    164                "Backwards branch with an uninitialized object in the local variables detected.");
    165        }
    166        // If we just didn't know that it was initialized, we have now learned.
    167        if (locals[i] instanceof UninitializedObjectType) {
    168            if (! (lv.locals[i] instanceof UninitializedObjectType)) {
    169                locals[i] = ((UninitializedObjectType) locals[i]).getInitialized();
    170            }
    171        }
    172        if ((locals[i] instanceof ReferenceType) && (lv.locals[i] instanceof ReferenceType)) {
    173            if (! locals[i].equals(lv.locals[i])) { // needed in case of two UninitializedObjectType instances
    174                final Type sup = ((ReferenceType) locals[i]).getFirstCommonSuperclass((ReferenceType) (lv.locals[i]));
    175
    176                if (sup != null) {
    177                    locals[i] = sup;
    178                }
    179                else{
    180                    // We should have checked this in Pass2!
    181                    throw new AssertionViolatedException(
    182                        "Could not load all the super classes of '"+locals[i]+"' and '"+lv.locals[i]+"'.");
    183                }
    184            }
    185        }
    186        else{
    187            if (! (locals[i].equals(lv.locals[i])) ) {
    188/*TODO
    189                if ((locals[i] instanceof org.apache.bcel.generic.ReturnaddressType) &&
    190                    (lv.locals[i] instanceof org.apache.bcel.generic.ReturnaddressType)) {
    191                    //System.err.println("merging "+locals[i]+" and "+lv.locals[i]);
    192                    throw new AssertionViolatedException("Merging different ReturnAddresses: '"+locals[i]+"' and '"+lv.locals[i]+"'.");
    193                }
    194*/
    195                locals[i] = Type.UNKNOWN;
    196            }
    197        }
    198        } catch (final ClassNotFoundException e) {
    199        // FIXME: maybe not the best way to handle this
    200        throw new AssertionViolatedException("Missing class: " + e, e);
    201        }
    202    }
    203
    204    /**
    205     * Returns a String representation of this object.
    206     */
    207    @Override
    208    public String toString() {
    209        final StringBuilder sb = new StringBuilder();
    210        for (int i=0; i<locals.length; i++) {
    211            sb.append(Integer.toString(i));
    212            sb.append(": ");
    213            sb.append(locals[i]);
    214            sb.append("\n");
    215        }
    216        return sb.toString();
    217    }
    218
    219    /**
    220     * Replaces all occurrences of {@code uninitializedObjectType} in this local variables set
    221     * with an "initialized" ObjectType.
    222     *
    223     * @param uninitializedObjectType the object to match.
    224     */
    225    public void initializeObject(final UninitializedObjectType uninitializedObjectType) {
    226        for (int i=0; i<locals.length; i++) {
    227            if (locals[i] == uninitializedObjectType) {
    228                locals[i] = uninitializedObjectType.getInitialized();
    229            }
    230        }
    231    }
    232}