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• ExecutionVisitor.java

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com.sun.org.apache.bcel.internal.verifier.structurals.ExecutionVisitor Maven / Gradle / Ivy

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 * 
 * Contributor(s):
 * 
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package com.sun.org.apache.bcel.internal.verifier.structurals;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 */

import com.sun.org.apache.bcel.internal.Constants;
import com.sun.org.apache.bcel.internal.Repository;
import com.sun.org.apache.bcel.internal.generic.*;
import com.sun.org.apache.bcel.internal.classfile.JavaClass;
import com.sun.org.apache.bcel.internal.classfile.Constant;
import com.sun.org.apache.bcel.internal.classfile.ConstantDouble;
import com.sun.org.apache.bcel.internal.classfile.ConstantFloat;
import com.sun.org.apache.bcel.internal.classfile.ConstantInteger;
import com.sun.org.apache.bcel.internal.classfile.ConstantLong;
import com.sun.org.apache.bcel.internal.classfile.ConstantString;
import com.sun.org.apache.bcel.internal.verifier.Verifier;
import com.sun.org.apache.bcel.internal.verifier.exc.*;
import java.util.ArrayList;
import java.util.Hashtable;

/**
 * This Visitor class may be used for a type-based Java Virtual Machine
 * simulation.
 * It does not check for correct types on the OperandStack or in the
 * LocalVariables; nor does it check their sizes are sufficiently big.
 * Thus, to use this Visitor for bytecode verifying, you have to make sure
 * externally that the type constraints of the Java Virtual Machine instructions
 * are satisfied. An InstConstraintVisitor may be used for this.
 * Anyway, this Visitor does not mandate it. For example, when you
 * visitIADD(IADD o), then there are two stack slots popped and one
 * stack slot containing a Type.INT is pushed (where you could also
 * pop only one slot if you know there are two Type.INT on top of the
 * stack). Monitor-specific behaviour is not simulated.
 * 
 * 
Conventions:
 *
 * Type.VOID will never be pushed onto the stack. Type.DOUBLE and Type.LONG
 * that would normally take up two stack slots (like Double_HIGH and
 * Double_LOW) are represented by a simple single Type.DOUBLE or Type.LONG
 * object on the stack here.
 * If a two-slot type is stored into a local variable, the next variable
 * is given the type Type.UNKNOWN.
 *
 * @version $Id: ExecutionVisitor.java,v 1.3 2007-07-19 04:35:00 ofung Exp $
 * @author Enver Haase
 * @see #visitDSTORE(DSTORE o)
 * @see InstConstraintVisitor
 */
public class ExecutionVisitor extends EmptyVisitor implements Visitor{

	/**
	 * The executionframe we're operating on.
	 */
	private Frame frame = null;

	/**
	 * The ConstantPoolGen we're working with.
	 * @see #setConstantPoolGen(ConstantPoolGen)
	 */
	private ConstantPoolGen cpg = null;

	/**
	 * Constructor. Constructs a new instance of this class.
	 */
	public ExecutionVisitor(){}

	/**
	 * The OperandStack from the current Frame we're operating on.
	 * @see #setFrame(Frame)
	 */
	private OperandStack stack(){
		return frame.getStack();
	}

	/**
	 * The LocalVariables from the current Frame we're operating on.
	 * @see #setFrame(Frame)
	 */
	private LocalVariables locals(){
		return frame.getLocals();
	}

	/**
	 * Sets the ConstantPoolGen needed for symbolic execution.
	 */
	public void setConstantPoolGen(ConstantPoolGen cpg){
		this.cpg = cpg;
	}
	
	/**
	 * The only method granting access to the single instance of
	 * the ExecutionVisitor class. Before actively using this
	 * instance, SET THE ConstantPoolGen FIRST.
	 * @see #setConstantPoolGen(ConstantPoolGen)
	 */
	public void setFrame(Frame f){
		this.frame = f;
	}

	///** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	//public void visitWIDE(WIDE o){
	// The WIDE instruction is modelled as a flag
	// of the embedded instructions in BCEL.
	// Therefore BCEL checks for possible errors
	// when parsing in the .class file: We don't
	// have even the possibilty to care for WIDE
	// here.
	//}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitAALOAD(AALOAD o){
		stack().pop();														// pop the index int
//System.out.print(stack().peek());
		Type t = stack().pop(); // Pop Array type
		if (t == Type.NULL){
			stack().push(Type.NULL);
		}	// Do nothing stackwise --- a NullPointerException is thrown at Run-Time
		else{
			ArrayType at = (ArrayType) t;	
			stack().push(at.getElementType());
		}
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitAASTORE(AASTORE o){
		stack().pop();
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitACONST_NULL(ACONST_NULL o){
		stack().push(Type.NULL);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitALOAD(ALOAD o){
		stack().push(locals().get(o.getIndex()));
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitANEWARRAY(ANEWARRAY o){
		stack().pop(); //count
		stack().push( new ArrayType(o.getType(cpg), 1) );
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitARETURN(ARETURN o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitARRAYLENGTH(ARRAYLENGTH o){
		stack().pop();
		stack().push(Type.INT);
	}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitASTORE(ASTORE o){
		locals().set(o.getIndex(), stack().pop());
		//System.err.println("TODO-DEBUG:	set LV '"+o.getIndex()+"' to '"+locals().get(o.getIndex())+"'.");
	}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitATHROW(ATHROW o){
		Type t = stack().pop();
		stack().clear();
		if (t.equals(Type.NULL))
			stack().push(Type.getType("Ljava/lang/NullPointerException;"));
		else
			stack().push(t);
	}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitBALOAD(BALOAD o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitBASTORE(BASTORE o){
		stack().pop();
		stack().pop();
		stack().pop();
	}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitBIPUSH(BIPUSH o){
		stack().push(Type.INT);
	}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitCALOAD(CALOAD o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitCASTORE(CASTORE o){
		stack().pop();
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitCHECKCAST(CHECKCAST o){
		// It's possibly wrong to do so, but SUN's
		// ByteCode verifier seems to do (only) this, too.
		// TODO: One could use a sophisticated analysis here to check
		//       if a type cannot possibly be cated to another and by
		//       so doing predict the ClassCastException at run-time.
		stack().pop();
		stack().push(o.getType(cpg));
	}

	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitD2F(D2F o){
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitD2I(D2I o){
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitD2L(D2L o){
		stack().pop();
		stack().push(Type.LONG);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDADD(DADD o){
		stack().pop();
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDALOAD(DALOAD o){
		stack().pop();
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDASTORE(DASTORE o){
		stack().pop();
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDCMPG(DCMPG o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDCMPL(DCMPL o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDCONST(DCONST o){
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDDIV(DDIV o){
		stack().pop();
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDLOAD(DLOAD o){
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDMUL(DMUL o){
		stack().pop();
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDNEG(DNEG o){
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDREM(DREM o){
		stack().pop();
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDRETURN(DRETURN o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDSTORE(DSTORE o){
		locals().set(o.getIndex(), stack().pop());
		locals().set(o.getIndex()+1, Type.UNKNOWN);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDSUB(DSUB o){
		stack().pop();
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDUP(DUP o){
		Type t = stack().pop();
		stack().push(t);
		stack().push(t);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDUP_X1(DUP_X1 o){
		Type w1 = stack().pop();
		Type w2 = stack().pop();
		stack().push(w1);
		stack().push(w2);
		stack().push(w1);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDUP_X2(DUP_X2 o){
		Type w1 = stack().pop();
		Type w2 = stack().pop();
		if (w2.getSize() == 2){
			stack().push(w1);
			stack().push(w2);
			stack().push(w1);
		}
		else{
			Type w3 = stack().pop();
			stack().push(w1);
			stack().push(w3);
			stack().push(w2);
			stack().push(w1);
		}
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDUP2(DUP2 o){
		Type t = stack().pop();
		if (t.getSize() == 2){
			stack().push(t);
			stack().push(t);
		}
		else{ // t.getSize() is 1
			Type u = stack().pop();
			stack().push(u);
			stack().push(t);
			stack().push(u);
			stack().push(t);
		}
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDUP2_X1(DUP2_X1 o){
		Type t = stack().pop();
		if (t.getSize() == 2){
			Type u = stack().pop();
			stack().push(t);
			stack().push(u);
			stack().push(t);
		}
		else{ //t.getSize() is1
			Type u = stack().pop();
			Type v = stack().pop();
			stack().push(u);
			stack().push(t);
			stack().push(v);
			stack().push(u);
			stack().push(t);
		}
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitDUP2_X2(DUP2_X2 o){
		Type t = stack().pop();
		if (t.getSize() == 2){
			Type u = stack().pop();
			if (u.getSize() == 2){
				stack().push(t);
				stack().push(u);
				stack().push(t);
			}else{
				Type v = stack().pop();
				stack().push(t);
				stack().push(v);
				stack().push(u);
				stack().push(t);
			}
		}
		else{ //t.getSize() is 1
			Type u = stack().pop();
			Type v = stack().pop();
			if (v.getSize() == 2){
				stack().push(u);
				stack().push(t);
				stack().push(v);
				stack().push(u);
				stack().push(t);
			}else{
				Type w = stack().pop();
				stack().push(u);
				stack().push(t);
				stack().push(w);
				stack().push(v);
				stack().push(u);
				stack().push(t);
			}
		}
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitF2D(F2D o){
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitF2I(F2I o){
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitF2L(F2L o){
		stack().pop();
		stack().push(Type.LONG);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFADD(FADD o){
		stack().pop();
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFALOAD(FALOAD o){
		stack().pop();
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFASTORE(FASTORE o){
		stack().pop();
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFCMPG(FCMPG o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFCMPL(FCMPL o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFCONST(FCONST o){
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFDIV(FDIV o){
		stack().pop();
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFLOAD(FLOAD o){
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFMUL(FMUL o){
		stack().pop();
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFNEG(FNEG o){
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFREM(FREM o){
		stack().pop();
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFRETURN(FRETURN o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFSTORE(FSTORE o){
		locals().set(o.getIndex(), stack().pop());
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitFSUB(FSUB o){
		stack().pop();
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitGETFIELD(GETFIELD o){
		stack().pop();
		Type t = o.getFieldType(cpg);
		if (	t.equals(Type.BOOLEAN)	||
					t.equals(Type.CHAR)			||
					t.equals(Type.BYTE) 		||
					t.equals(Type.SHORT)		)
			t = Type.INT;
		stack().push(t);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitGETSTATIC(GETSTATIC o){
		Type t = o.getFieldType(cpg);
		if (	t.equals(Type.BOOLEAN)	||
					t.equals(Type.CHAR)			||
					t.equals(Type.BYTE) 		||
					t.equals(Type.SHORT)		)
			t = Type.INT;
		stack().push(t);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitGOTO(GOTO o){
		// no stack changes.
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitGOTO_W(GOTO_W o){
		// no stack changes.
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitI2B(I2B o){
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitI2C(I2C o){
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitI2D(I2D o){
		stack().pop();
		stack().push(Type.DOUBLE);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitI2F(I2F o){
		stack().pop();
		stack().push(Type.FLOAT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitI2L(I2L o){
		stack().pop();
		stack().push(Type.LONG);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitI2S(I2S o){
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIADD(IADD o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIALOAD(IALOAD o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIAND(IAND o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIASTORE(IASTORE o){
		stack().pop();
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitICONST(ICONST o){
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIDIV(IDIV o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ACMPEQ(IF_ACMPEQ o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ACMPNE(IF_ACMPNE o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ICMPEQ(IF_ICMPEQ o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ICMPGE(IF_ICMPGE o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ICMPGT(IF_ICMPGT o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ICMPLE(IF_ICMPLE o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ICMPLT(IF_ICMPLT o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIF_ICMPNE(IF_ICMPNE o){
		stack().pop();
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFEQ(IFEQ o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFGE(IFGE o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFGT(IFGT o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFLE(IFLE o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFLT(IFLT o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFNE(IFNE o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFNONNULL(IFNONNULL o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIFNULL(IFNULL o){
		stack().pop();
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIINC(IINC o){
		// stack is not changed.
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitILOAD(ILOAD o){
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitIMUL(IMUL o){
		stack().pop();
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitINEG(INEG o){
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitINSTANCEOF(INSTANCEOF o){
		stack().pop();
		stack().push(Type.INT);
	}
	/** Symbolically executes the corresponding Java Virtual Machine instruction. */ 
	public void visitINVOKEINTERFACE(INVOKEINTERFACE o){
		stack().pop();	//objectref
		for (int i=0; i