1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.bcel.verifier.structurals;
18
19 import org.apache.bcel.generic.ReferenceType;
20 import org.apache.bcel.generic.Type;
21 import org.apache.bcel.verifier.exc.AssertionViolatedException;
22 import org.apache.bcel.verifier.exc.StructuralCodeConstraintException;
23 import org.apache.commons.lang3.ArrayFill;
24
25 /**
26 * This class implements an array of local variables used for symbolic JVM simulation.
27 */
28 public class LocalVariables implements Cloneable {
29
30 /** The Type[] containing the local variable slots. */
31 private final Type[] locals;
32
33 /**
34 * Creates a new LocalVariables object.
35 *
36 * @param localVariableCount local variable count.
37 */
38 public LocalVariables(final int localVariableCount) {
39 locals = ArrayFill.fill(new Type[localVariableCount], Type.UNKNOWN);
40 }
41
42 /**
43 * Returns a deep copy of this object; i.e. the clone operates on a new local variable array. However, the Type objects
44 * in the array are shared.
45 */
46 @Override
47 public Object clone() {
48 final LocalVariables lvs = new LocalVariables(locals.length);
49 System.arraycopy(this.locals, 0, lvs.locals, 0, locals.length);
50 return lvs;
51 }
52
53 /*
54 * Fulfills the general contract of Object.equals().
55 */
56 @Override
57 public boolean equals(final Object o) {
58 if (!(o instanceof LocalVariables)) {
59 return false;
60 }
61 final LocalVariables lv = (LocalVariables) o;
62 if (this.locals.length != lv.locals.length) {
63 return false;
64 }
65 for (int i = 0; i < this.locals.length; i++) {
66 if (!this.locals[i].equals(lv.locals[i])) {
67 // System.out.println(this.locals[i]+" is not "+lv.locals[i]);
68 return false;
69 }
70 }
71 return true;
72 }
73
74 /**
75 * Returns the type of the local variable slot index.
76 *
77 * @param slotIndex Slot to look up.
78 * @return the type of the local variable slot index.
79 */
80 public Type get(final int slotIndex) {
81 return locals[slotIndex];
82 }
83
84 /**
85 * Returns a (correctly typed) clone of this object. This is equivalent to ((LocalVariables) this.clone()).
86 *
87 * @return a (correctly typed) clone of this object.
88 */
89 public LocalVariables getClone() {
90 return (LocalVariables) this.clone();
91 }
92
93 /**
94 * @return a hash code value for the object.
95 */
96 @Override
97 public int hashCode() {
98 return locals.length;
99 }
100
101 /**
102 * Replaces all occurrences of {@code uninitializedObjectType} in this local variables set with an "initialized"
103 * ObjectType.
104 *
105 * @param uninitializedObjectType the object to match.
106 */
107 public void initializeObject(final UninitializedObjectType uninitializedObjectType) {
108 for (int i = 0; i < locals.length; i++) {
109 if (locals[i] == uninitializedObjectType) {
110 locals[i] = uninitializedObjectType.getInitialized();
111 }
112 }
113 }
114
115 /**
116 * Returns the number of local variable slots.
117 *
118 * @return the number of local variable slots.
119 */
120 public int maxLocals() {
121 return locals.length;
122 }
123
124 /**
125 * Merges two local variables sets as described in the Java Virtual Machine Specification, Second Edition, section
126 * 4.9.2, page 146.
127 *
128 * @param localVariable other local variable.
129 */
130 public void merge(final LocalVariables localVariable) {
131
132 if (this.locals.length != localVariable.locals.length) {
133 throw new AssertionViolatedException("Merging LocalVariables of different size?!? From different methods or what?!?");
134 }
135
136 for (int i = 0; i < locals.length; i++) {
137 merge(localVariable, i);
138 }
139 }
140
141 /**
142 * Merges a single local variable.
143 *
144 * @see #merge(LocalVariables)
145 */
146 private void merge(final LocalVariables lv, final int i) {
147 try {
148
149 // We won't accept an unitialized object if we know it was initialized;
150 // compare vmspec2, 4.9.4, last paragraph.
151 if (!(locals[i] instanceof UninitializedObjectType) && lv.locals[i] instanceof UninitializedObjectType) {
152 throw new StructuralCodeConstraintException("Backwards branch with an uninitialized object in the local variables detected.");
153 }
154 // Even harder, what about _different_ uninitialized object types?!
155 if (!locals[i].equals(lv.locals[i]) && locals[i] instanceof UninitializedObjectType && lv.locals[i] instanceof UninitializedObjectType) {
156 throw new StructuralCodeConstraintException("Backwards branch with an uninitialized object in the local variables detected.");
157 }
158 // If we just didn't know that it was initialized, we have now learned.
159 if (locals[i] instanceof UninitializedObjectType && !(lv.locals[i] instanceof UninitializedObjectType)) {
160 locals[i] = ((UninitializedObjectType) locals[i]).getInitialized();
161 }
162 if (locals[i] instanceof ReferenceType && lv.locals[i] instanceof ReferenceType) {
163 if (!locals[i].equals(lv.locals[i])) { // needed in case of two UninitializedObjectType instances
164 final Type sup = ((ReferenceType) locals[i]).getFirstCommonSuperclass((ReferenceType) lv.locals[i]);
165
166 if (sup == null) {
167 // We should have checked this in Pass2!
168 throw new AssertionViolatedException("Could not load all the super classes of '" + locals[i] + "' and '" + lv.locals[i] + "'.");
169 }
170 locals[i] = sup;
171 }
172 } else if (!locals[i].equals(lv.locals[i])) {
173 /*
174 * TODO if ((locals[i] instanceof org.apache.bcel.generic.ReturnaddressType) && (lv.locals[i] instanceof
175 * org.apache.bcel.generic.ReturnaddressType)) { //System.err.println("merging "+locals[i]+" and "+lv.locals[i]); throw
176 * new AssertionViolatedException("Merging different ReturnAddresses: '"+locals[i]+"' and '"+lv.locals[i]+"'."); }
177 */
178 locals[i] = Type.UNKNOWN;
179 }
180 } catch (final ClassNotFoundException e) {
181 // FIXME: maybe not the best way to handle this
182 throw new AssertionViolatedException("Missing class: " + e, e);
183 }
184 }
185
186 /**
187 * Sets a new Type for the given local variable slot.
188 *
189 * @param slotIndex Target slot index.
190 * @param type Type to save at the given slot index.
191 */
192 public void set(final int slotIndex, final Type type) { // TODO could be package-protected?
193 if (type == Type.BYTE || type == Type.SHORT || type == Type.BOOLEAN || type == Type.CHAR) {
194 throw new AssertionViolatedException("LocalVariables do not know about '" + type + "'. Use Type.INT instead.");
195 }
196 locals[slotIndex] = type;
197 }
198
199 /**
200 * Returns a String representation of this object.
201 */
202 @Override
203 public String toString() {
204 final StringBuilder sb = new StringBuilder();
205 for (int i = 0; i < locals.length; i++) {
206 sb.append(Integer.toString(i));
207 sb.append(": ");
208 sb.append(locals[i]);
209 sb.append("\n");
210 }
211 return sb.toString();
212 }
213 }