ExceptionInstructionChecker.java revision cfead78069f3dc32998dc118ee08cab3867acea2 
1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2011 Eric Lafortune (eric@graphics.cornell.edu)
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the Free
9 * Software Foundation; either version 2 of the License, or (at your option)
10 * any later version.
11 *
12 * This program is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 * more details.
16 *
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 */
21package proguard.optimize.info;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.CodeAttribute;
25import proguard.classfile.constant.RefConstant;
26import proguard.classfile.constant.visitor.ConstantVisitor;
27import proguard.classfile.instruction.*;
28import proguard.classfile.instruction.visitor.InstructionVisitor;
29import proguard.classfile.util.SimplifiedVisitor;
30import proguard.classfile.visitor.MemberVisitor;
31
32/**
33 * This class can tell whether an instruction might throw exceptions.
34 *
35 * @author Eric Lafortune
36 */
37public class ExceptionInstructionChecker
38extends      SimplifiedVisitor
39implements   InstructionVisitor
40//             ConstantVisitor,
41//             MemberVisitor
42{
43    // A return value for the visitor methods.
44    private boolean mayThrowExceptions;
45
46
47    /**
48     * Returns whether the given instruction may throw exceptions.
49     */
50    public boolean mayThrowExceptions(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction)
51    {
52        mayThrowExceptions = false;
53
54        instruction.accept(clazz, method,  codeAttribute, offset, this);
55
56        return mayThrowExceptions;
57    }
58
59
60    // Implementations for InstructionVisitor.
61
62    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}
63
64
65    public void visitSimpleInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, SimpleInstruction simpleInstruction)
66    {
67        byte opcode = simpleInstruction.opcode;
68
69        // Check for instructions that may throw exceptions.
70        // Note that monitorexit can not sensibly throw exceptions, except the
71        // broken and deprecated asynchronous ThreadDeath. Removing the
72        // artificial infinite looping exception blocks that recent compilers
73        // add does not strictly follow the JVM specs, but it does have the
74        // additional benefit of avoiding a bug in the JVM in JDK 1.1.
75        switch (opcode)
76        {
77            case InstructionConstants.OP_IDIV:
78            case InstructionConstants.OP_LDIV:
79            case InstructionConstants.OP_IREM:
80            case InstructionConstants.OP_LREM:
81            case InstructionConstants.OP_IALOAD:
82            case InstructionConstants.OP_LALOAD:
83            case InstructionConstants.OP_FALOAD:
84            case InstructionConstants.OP_DALOAD:
85            case InstructionConstants.OP_AALOAD:
86            case InstructionConstants.OP_BALOAD:
87            case InstructionConstants.OP_CALOAD:
88            case InstructionConstants.OP_SALOAD:
89            case InstructionConstants.OP_IASTORE:
90            case InstructionConstants.OP_LASTORE:
91            case InstructionConstants.OP_FASTORE:
92            case InstructionConstants.OP_DASTORE:
93            case InstructionConstants.OP_AASTORE:
94            case InstructionConstants.OP_BASTORE:
95            case InstructionConstants.OP_CASTORE:
96            case InstructionConstants.OP_SASTORE:
97            case InstructionConstants.OP_NEWARRAY:
98            case InstructionConstants.OP_ARRAYLENGTH:
99            case InstructionConstants.OP_ATHROW:
100            case InstructionConstants.OP_MONITORENTER:
101                // These instructions may throw exceptions.
102                mayThrowExceptions = true;
103        }
104
105    }
106
107
108    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)
109    {
110        byte opcode = constantInstruction.opcode;
111
112        // Check for instructions that may throw exceptions.
113        switch (opcode)
114        {
115            case InstructionConstants.OP_GETSTATIC:
116            case InstructionConstants.OP_PUTSTATIC:
117            case InstructionConstants.OP_GETFIELD:
118            case InstructionConstants.OP_PUTFIELD:
119            case InstructionConstants.OP_INVOKEVIRTUAL:
120            case InstructionConstants.OP_INVOKESPECIAL:
121            case InstructionConstants.OP_INVOKESTATIC:
122            case InstructionConstants.OP_INVOKEINTERFACE:
123            case InstructionConstants.OP_INVOKEDYNAMIC:
124            case InstructionConstants.OP_NEW:
125            case InstructionConstants.OP_ANEWARRAY:
126            case InstructionConstants.OP_CHECKCAST:
127            case InstructionConstants.OP_INSTANCEOF:
128            case InstructionConstants.OP_MULTIANEWARRAY:
129                // These instructions may throw exceptions.
130                mayThrowExceptions = true;
131        }
132
133//          case InstructionConstants.OP_INVOKEVIRTUAL:
134//          case InstructionConstants.OP_INVOKESPECIAL:
135//          case InstructionConstants.OP_INVOKESTATIC:
136//          case InstructionConstants.OP_INVOKEINTERFACE:
137//            // Check if the invoking the method may throw an exception.
138//            clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
139    }
140
141
142//    // Implementations for ConstantVisitor.
143//
144//    public void visitAnyMethodrefConstant(Clazz clazz, RefConstant refConstant)
145//    {
146//        Member referencedMember = refConstant.referencedMember;
147//
148//        // Do we have a reference to the method?
149//        if (referencedMember == null)
150//        {
151//            // We'll have to assume invoking the unknown method may throw an
152//            // an exception.
153//            mayThrowExceptions = true;
154//        }
155//        else
156//        {
157//            // First check the referenced method itself.
158//            refConstant.referencedMemberAccept(this);
159//
160//            // If the result isn't conclusive, check down the hierarchy.
161//            if (!mayThrowExceptions)
162//            {
163//                Clazz  referencedClass  = refConstant.referencedClass;
164//                Method referencedMethod = (Method)referencedMember;
165//
166//                // Check all other implementations of the method in the class
167//                // hierarchy.
168//                referencedClass.methodImplementationsAccept(referencedMethod,
169//                                                            false,
170//                                                            false,
171//                                                            true,
172//                                                            true,
173//                                                            this);
174//            }
175//        }
176//    }
177//
178//
179//    // Implementations for MemberVisitor.
180//
181//    public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
182//    {
183//        mayThrowExceptions = mayThrowExceptions ||
184//                             ExceptionMethodMarker.mayThrowExceptions(programMethod);
185//    }
186//
187//
188//    public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)
189//    {
190//        mayThrowExceptions = mayThrowExceptions ||
191//                             !NoExceptionMethodMarker.doesntThrowExceptions(libraryMethod);
192//    }
193}
194