ExceptionInstructionChecker.java revision 9f606f95f03a75961498803e24bee6799a7c0885 
1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2009 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        if (opcode == InstructionConstants.OP_IDIV         ||
71            opcode == InstructionConstants.OP_LDIV         ||
72            opcode == InstructionConstants.OP_IREM         ||
73            opcode == InstructionConstants.OP_LREM         ||
74            opcode == InstructionConstants.OP_IALOAD       ||
75            opcode == InstructionConstants.OP_LALOAD       ||
76            opcode == InstructionConstants.OP_FALOAD       ||
77            opcode == InstructionConstants.OP_DALOAD       ||
78            opcode == InstructionConstants.OP_AALOAD       ||
79            opcode == InstructionConstants.OP_BALOAD       ||
80            opcode == InstructionConstants.OP_CALOAD       ||
81            opcode == InstructionConstants.OP_SALOAD       ||
82            opcode == InstructionConstants.OP_IASTORE      ||
83            opcode == InstructionConstants.OP_LASTORE      ||
84            opcode == InstructionConstants.OP_FASTORE      ||
85            opcode == InstructionConstants.OP_DASTORE      ||
86            opcode == InstructionConstants.OP_AASTORE      ||
87            opcode == InstructionConstants.OP_BASTORE      ||
88            opcode == InstructionConstants.OP_CASTORE      ||
89            opcode == InstructionConstants.OP_SASTORE      ||
90            opcode == InstructionConstants.OP_NEWARRAY     ||
91            opcode == InstructionConstants.OP_ARRAYLENGTH  ||
92            opcode == InstructionConstants.OP_ATHROW       ||
93            opcode == InstructionConstants.OP_MONITORENTER ||
94            opcode == InstructionConstants.OP_MONITOREXIT)
95        {
96            // These instructions may throw exceptions.
97            mayThrowExceptions = true;
98        }
99
100    }
101
102
103    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)
104    {
105        byte opcode = constantInstruction.opcode;
106
107        // Check for instructions that may throw exceptions.
108        if (opcode == InstructionConstants.OP_GETSTATIC       ||
109            opcode == InstructionConstants.OP_PUTSTATIC       ||
110            opcode == InstructionConstants.OP_GETFIELD        ||
111            opcode == InstructionConstants.OP_PUTFIELD        ||
112            opcode == InstructionConstants.OP_INVOKEVIRTUAL   ||
113            opcode == InstructionConstants.OP_INVOKESPECIAL   ||
114            opcode == InstructionConstants.OP_INVOKESTATIC    ||
115            opcode == InstructionConstants.OP_INVOKEINTERFACE ||
116            opcode == InstructionConstants.OP_NEW             ||
117            opcode == InstructionConstants.OP_ANEWARRAY       ||
118            opcode == InstructionConstants.OP_CHECKCAST       ||
119            opcode == InstructionConstants.OP_MULTIANEWARRAY)
120        {
121            // These instructions may throw exceptions.
122            mayThrowExceptions = true;
123        }
124//        else
125//        if (opcode == InstructionConstants.OP_INVOKEVIRTUAL   ||
126//            opcode == InstructionConstants.OP_INVOKESPECIAL   ||
127//            opcode == InstructionConstants.OP_INVOKESTATIC    ||
128//            opcode == InstructionConstants.OP_INVOKEINTERFACE)
129//        {
130//            // Check if the invoking the method may throw an exception.
131//            clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
132//        }
133    }
134
135
136//    // Implementations for ConstantVisitor.
137//
138//    public void visitAnyMethodrefConstant(Clazz clazz, RefConstant refConstant)
139//    {
140//        Member referencedMember = refConstant.referencedMember;
141//
142//        // Do we have a reference to the method?
143//        if (referencedMember == null)
144//        {
145//            // We'll have to assume invoking the unknown method may throw an
146//            // an exception.
147//            mayThrowExceptions = true;
148//        }
149//        else
150//        {
151//            // First check the referenced method itself.
152//            refConstant.referencedMemberAccept(this);
153//
154//            // If the result isn't conclusive, check down the hierarchy.
155//            if (!mayThrowExceptions)
156//            {
157//                Clazz  referencedClass  = refConstant.referencedClass;
158//                Method referencedMethod = (Method)referencedMember;
159//
160//                // Check all other implementations of the method in the class
161//                // hierarchy.
162//                referencedClass.methodImplementationsAccept(referencedMethod,
163//                                                            false,
164//                                                            false,
165//                                                            true,
166//                                                            true,
167//                                                            this);
168//            }
169//        }
170//    }
171//
172//
173//    // Implementations for MemberVisitor.
174//
175//    public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
176//    {
177//        mayThrowExceptions = mayThrowExceptions ||
178//                             ExceptionMethodMarker.mayThrowExceptions(programMethod);
179//    }
180//
181//
182//    public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)
183//    {
184//        mayThrowExceptions = mayThrowExceptions ||
185//                             !NoExceptionMethodMarker.doesntThrowExceptions(libraryMethod);
186//    }
187}
188