asm4/test/perf/org/apache/bcel/verifier/structurals/ModifiedPass3bVerifier.java - toolchain/jill - Git at Google

 /*
  * Copyright  2000-2004 The Apache Software Foundation
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS,
  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  *
  */
 package org.apache.bcel.verifier.structurals;


 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Random;
 import java.util.Vector;

 import org.apache.bcel.Constants;
 import org.apache.bcel.classfile.JavaClass;
 import org.apache.bcel.classfile.Method;
 import org.apache.bcel.generic.ConstantPoolGen;
 import org.apache.bcel.generic.GETFIELD;
 import org.apache.bcel.generic.InstructionHandle;
 import org.apache.bcel.generic.InvokeInstruction;
 import org.apache.bcel.generic.JsrInstruction;
 import org.apache.bcel.generic.LoadInstruction;
 import org.apache.bcel.generic.MethodGen;
 import org.apache.bcel.generic.ObjectType;
 import org.apache.bcel.generic.RET;
 import org.apache.bcel.generic.ReturnInstruction;
 import org.apache.bcel.generic.ReturnaddressType;
 import org.apache.bcel.generic.Type;
 import org.apache.bcel.verifier.PassVerifier;
 import org.apache.bcel.verifier.VerificationResult;
 import org.apache.bcel.verifier.exc.AssertionViolatedException;
 import org.apache.bcel.verifier.exc.StructuralCodeConstraintException;
 import org.apache.bcel.verifier.exc.VerifierConstraintViolatedException;

 /**
  * This PassVerifier verifies a method of class file according to pass 3,
  * so-called structural verification as described in The Java Virtual Machine
  * Specification, 2nd edition.
  * More detailed information is to be found at the do_verify() method's
  * documentation.
  *
  * @version $Id: ModifiedPass3bVerifier.java,v 1.3 2007-11-08 17:22:56 ebruneton Exp $
  * @author Enver Haase
  * @see #do_verify()
  */

 public final class ModifiedPass3bVerifier extends PassVerifier{
     /* TODO:    Throughout pass 3b, upper halves of LONG and DOUBLE
                         are represented by Type.UNKNOWN. This should be changed
                         in favour of LONG_Upper and DOUBLE_Upper as in pass 2. */

     /**
      * An InstructionContextQueue is a utility class that holds
      * (InstructionContext, ArrayList) pairs in a Queue data structure.
      * This is used to hold information about InstructionContext objects
      * externally --- i.e. that information is not saved inside the
      * InstructionContext object itself. This is useful to save the
      * execution path of the symbolic execution of the
      * Pass3bVerifier - this is not information
      * that belongs into the InstructionContext object itself.
      * Only at "execute()"ing
      * time, an InstructionContext object will get the current information
      * we have about its symbolic execution predecessors.
      */
     static final class InstructionContextQueue{
         private List<InstructionContext> ics = new Vector<InstructionContext>(); // Type: InstructionContext
         private List<ArrayList<InstructionContext>> ecs = new Vector<ArrayList<InstructionContext>>(); // Type: ArrayList (of InstructionContext)
         public void add(InstructionContext ic, ArrayList<InstructionContext> executionChain){
             ics.add(ic);
             ecs.add(executionChain);
         }
         public boolean isEmpty(){
             return ics.isEmpty();
         }
         public void remove(){
             this.remove(0);
         }
         public void remove(int i){
             ics.remove(i);
             ecs.remove(i);
         }
         public InstructionContext getIC(int i){
             return ics.get(i);
         }
         public ArrayList<InstructionContext> getEC(int i){
             return ecs.get(i);
         }
         public int size(){
             return ics.size();
         }
     } // end Inner Class InstructionContextQueue

     /** In DEBUG mode, the verification algorithm is not randomized. */
     private static final boolean DEBUG = true;

     private JavaClass jc;

     /** The method number to verify. */
     private int method_no;

     /**
      * This class should only be instantiated by a Verifier.
      *
      * @see org.apache.bcel.verifier.Verifier
      */
     public ModifiedPass3bVerifier(JavaClass jc, int method_no){
         this.jc = jc;
         this.method_no = method_no;
     }

     /**
      * Whenever the outgoing frame
      * situation of an InstructionContext changes, all its successors are
      * put [back] into the queue [as if they were unvisited].
    * The proof of termination is about the existence of a
    * fix point of frame merging.
      */
     private void circulationPump(MethodGen m,ControlFlowGraph cfg, InstructionContext start, Frame vanillaFrame, InstConstraintVisitor icv, ExecutionVisitor ev){
         final Random random = new Random();
         InstructionContextQueue icq = new InstructionContextQueue();

         start.execute(vanillaFrame, new ArrayList<InstructionContext>(), icv, ev);  // new ArrayList() <=>  no Instruction was executed before
                                                                                                     //                                  => Top-Level routine (no jsr call before)
         icq.add(start, new ArrayList<InstructionContext>());

         // LOOP!
         while (!icq.isEmpty()){
             InstructionContext u;
             ArrayList<InstructionContext> ec;
             if (!DEBUG){
                 int r = random.nextInt(icq.size());
                 u = icq.getIC(r);
                 ec = icq.getEC(r);
                 icq.remove(r);
             }
             else{
                 u  = icq.getIC(0);
                 ec = icq.getEC(0);
                 icq.remove(0);
             }

             ArrayList<InstructionContext> oldchain = new ArrayList<InstructionContext>(ec);
             ArrayList<InstructionContext> newchain = new ArrayList<InstructionContext>(ec);
             newchain.add(u);

             if ((u.getInstruction().getInstruction()) instanceof RET){
 //System.err.println(u);
                 // We can only follow _one_ successor, the one after the
                 // JSR that was recently executed.
                 RET ret = (RET) (u.getInstruction().getInstruction());
                 ReturnaddressType t = (ReturnaddressType) u.getOutFrame(oldchain).getLocals().get(ret.getIndex());
                 InstructionContext theSuccessor = cfg.contextOf(t.getTarget());

                 // Sanity check
                 InstructionContext lastJSR = null;
                 int skip_jsr = 0;
                 for (int ss=oldchain.size()-1; ss >= 0; ss--){
                     if (skip_jsr < 0){
                         throw new AssertionViolatedException("More RET than JSR in execution chain?!");
                     }
 //System.err.println("+"+oldchain.get(ss));
                     if ((oldchain.get(ss)).getInstruction().getInstruction() instanceof JsrInstruction){
                         if (skip_jsr == 0){
                             lastJSR = oldchain.get(ss);
                             break;
                         }
                         else{
                             skip_jsr--;
                         }
                     }
                     if ((oldchain.get(ss)).getInstruction().getInstruction() instanceof RET){
                         skip_jsr++;
                     }
                 }
                 if (lastJSR == null){
                     throw new AssertionViolatedException("RET without a JSR before in ExecutionChain?! EC: '"+oldchain+"'.");
                 }
                 JsrInstruction jsr = (JsrInstruction) (lastJSR.getInstruction().getInstruction());
                 if ( theSuccessor != (cfg.contextOf(jsr.physicalSuccessor())) ){
                     throw new AssertionViolatedException("RET '"+u.getInstruction()+"' info inconsistent: jump back to '"+theSuccessor+"' or '"+cfg.contextOf(jsr.physicalSuccessor())+"'?");
                 }

                 if (theSuccessor.execute(u.getOutFrame(oldchain), newchain, icv, ev)){
                     icq.add(theSuccessor, new ArrayList<InstructionContext> (newchain));
                 }
             }
             else{// "not a ret"

                 // Normal successors. Add them to the queue of successors.
                 InstructionContext[] succs = u.getSuccessors();
                 for (int s=0; s<succs.length; s++){
                     InstructionContext v = succs[s];
                     if (v.execute(u.getOutFrame(oldchain), newchain, icv, ev)){
                         icq.add(v, new ArrayList<InstructionContext> (newchain));
                     }
                 }
             }// end "not a ret"

             // Exception Handlers. Add them to the queue of successors.
             // [subroutines are never protected; mandated by JustIce]
             ExceptionHandler[] exc_hds = u.getExceptionHandlers();
             for (int s=0; s<exc_hds.length; s++){
                 InstructionContext v = cfg.contextOf(exc_hds[s].getHandlerStart());
                 // TODO: the "oldchain" and "newchain" is used to determine the subroutine
                 // we're in (by searching for the last JSR) by the InstructionContext
                 // implementation. Therefore, we should not use this chain mechanism
                 // when dealing with exception handlers.
                 // Example: a JSR with an exception handler as its successor does not
                 // mean we're in a subroutine if we go to the exception handler.
                 // We should address this problem later; by now we simply "cut" the chain
                 // by using an empty chain for the exception handlers.
                 //if (v.execute(new Frame(u.getOutFrame(oldchain).getLocals(), new OperandStack (u.getOutFrame().getStack().maxStack(), (exc_hds[s].getExceptionType()==null? Type.THROWABLE : exc_hds[s].getExceptionType())) ), newchain), icv, ev){
                     //icq.add(v, (ArrayList) newchain.clone());
                 if (v.execute(new Frame(u.getOutFrame(oldchain).getLocals(), new OperandStack (u.getOutFrame(oldchain).getStack().maxStack(), (exc_hds[s].getExceptionType()==null? Type.THROWABLE : exc_hds[s].getExceptionType())) ), new ArrayList<InstructionContext>(), icv, ev)){
                     icq.add(v, new ArrayList<InstructionContext>());
                 }
             }

         }// while (!icq.isEmpty()) END

         InstructionHandle ih = start.getInstruction();
         do{
             if ((ih.getInstruction() instanceof ReturnInstruction) && (!(cfg.isDead(ih)))) {
                 InstructionContext ic = cfg.contextOf(ih);
                 Frame f = ic.getOutFrame(new ArrayList<InstructionContext>()); // TODO: This is buggy, we check only the top-level return instructions this way. Maybe some maniac returns from a method when in a subroutine?
                 LocalVariables lvs = f.getLocals();
                 for (int i=0; i<lvs.maxLocals(); i++){
                     if (lvs.get(i) instanceof UninitializedObjectType){
                         this.addMessage("Warning: ReturnInstruction '"+ic+"' may leave method with an uninitialized object in the local variables array '"+lvs+"'.");
                     }
                 }
                 OperandStack os = f.getStack();
                 for (int i=0; i<os.size(); i++){
                     if (os.peek(i) instanceof UninitializedObjectType){
                         this.addMessage("Warning: ReturnInstruction '"+ic+"' may leave method with an uninitialized object on the operand stack '"+os+"'.");
                     }
                 }
                 //see JVM $4.8.2
                 //TODO implement all based on stack
                 Type returnedType = null;
                 if( ih.getPrev().getInstruction() instanceof InvokeInstruction )
                 {
                     returnedType = ((InvokeInstruction)ih.getPrev().getInstruction()).getType(m.getConstantPool());
                 }
                 if( ih.getPrev().getInstruction() instanceof LoadInstruction )
                 {
                     int index = ((LoadInstruction)ih.getPrev().getInstruction()).getIndex();
                     returnedType = lvs.get(index);
                 }
                 if( ih.getPrev().getInstruction() instanceof GETFIELD )
                 {
                     returnedType = ((GETFIELD)ih.getPrev().getInstruction()).getType(m.getConstantPool());
                 }
                 if( returnedType != null )
                 {
                     if( returnedType instanceof ObjectType )
                     {
                         try
                         {
                             if( !((ObjectType)returnedType).isAssignmentCompatibleWith(m.getReturnType()) )
                             {
                                 throw new StructuralCodeConstraintException("Returned type "+returnedType+" does not match Method's return type "+m.getReturnType());
                             }
                         }
                         catch (Exception e)
                         {
                             //dont know what do do now, so raise RuntimeException
                             throw new RuntimeException(e);
                         }
                     }
                     else if( !returnedType.equals(m.getReturnType()) )
                     {
                         throw new StructuralCodeConstraintException("Returned type "+returnedType+" does not match Method's return type "+m.getReturnType());
                     }
                 }
             }
         }while ((ih = ih.getNext()) != null);

     }

     /**
      * Pass 3b implements the data flow analysis as described in the Java Virtual
      * Machine Specification, Second Edition.
      * Later versions will use LocalVariablesInfo objects to verify if the
      * verifier-inferred types and the class file's debug information (LocalVariables
      * attributes) match [TODO].
      *
      * @see org.apache.bcel.verifier.statics.LocalVariablesInfo
      * @see org.apache.bcel.verifier.statics.Pass2Verifier#getLocalVariablesInfo(int)
      */
     @Override
     public VerificationResult do_verify(){
         /*if (! myOwner.doPass3a(method_no).equals(VerificationResult.VR_OK)){
             return VerificationResult.VR_NOTYET;
         }

         // Pass 3a ran before, so it's safe to assume the JavaClass object is
         // in the BCEL repository.
         JavaClass jc;
         try {
             jc = Repository.lookupClass(myOwner.getClassName());
         } catch (ClassNotFoundException e) {
             // FIXME: maybe not the best way to handle this
             throw new AssertionViolatedException("Missing class: " + e.toString());
         }*/

         ConstantPoolGen constantPoolGen = new ConstantPoolGen(jc.getConstantPool());
         // Init Visitors
         InstConstraintVisitor icv = new InstConstraintVisitor();
         icv.setConstantPoolGen(constantPoolGen);

         ExecutionVisitor ev = new ExecutionVisitor();
         ev.setConstantPoolGen(constantPoolGen);

         Method[] methods = jc.getMethods(); // Method no "method_no" exists, we ran Pass3a before on it!

         try{

             MethodGen mg = new MethodGen(methods[method_no], jc.getClassName(), constantPoolGen);

             icv.setMethodGen(mg);

             ////////////// DFA BEGINS HERE ////////////////
             if (! (mg.isAbstract() || mg.isNative()) ){ // IF mg HAS CODE (See pass 2)

                 ControlFlowGraph cfg = new ControlFlowGraph(mg);

                 // Build the initial frame situation for this method.
                 Frame f = new Frame(mg.getMaxLocals(),mg.getMaxStack());
                 if ( !mg.isStatic() ){
                     if (mg.getName().equals(Constants.CONSTRUCTOR_NAME)){
                         Frame._this = new UninitializedObjectType(new ObjectType(jc.getClassName()));
                         f.getLocals().set(0, Frame._this);
                     }
                     else{
                         Frame._this = null;
                         f.getLocals().set(0, new ObjectType(jc.getClassName()));
                     }
                 }
                 Type[] argtypes = mg.getArgumentTypes();
                 int twoslotoffset = 0;
                 for (int j=0; j<argtypes.length; j++){
                     if (argtypes[j] == Type.SHORT || argtypes[j] == Type.BYTE || argtypes[j] == Type.CHAR || argtypes[j] == Type.BOOLEAN){
                         argtypes[j] = Type.INT;
                     }
                     f.getLocals().set(twoslotoffset + j + (mg.isStatic()?0:1), argtypes[j]);
                     if (argtypes[j].getSize() == 2){
                         twoslotoffset++;
                         f.getLocals().set(twoslotoffset + j + (mg.isStatic()?0:1), Type.UNKNOWN);
                     }
                 }
                 circulationPump(mg,cfg, cfg.contextOf(mg.getInstructionList().getStart()), f, icv, ev);
             }
         }
         catch (VerifierConstraintViolatedException ce){
             ce.extendMessage("Constraint violated in method '"+methods[method_no]+"':\n","");
             return new VerificationResult(VerificationResult.VERIFIED_REJECTED, ce.getMessage());
         }
         catch (RuntimeException re){
             // These are internal errors

             StringWriter sw = new StringWriter();
             PrintWriter pw = new PrintWriter(sw);
             re.printStackTrace(pw);

             throw new AssertionViolatedException("Some RuntimeException occured while verify()ing class '"+jc.getClassName()+"', method '"+methods[method_no]+"'. Original RuntimeException's stack trace:\n---\n"+sw+"---\n");
         }
         return VerificationResult.VR_OK;
     }

     /** Returns the method number as supplied when instantiating. */
     public int getMethodNo(){
         return method_no;
     }
 }
	/*
	* Copyright 2000-2004 The Apache Software Foundation
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*
	*/
	package org.apache.bcel.verifier.structurals;


	import java.io.PrintWriter;
	import java.io.StringWriter;
	import java.util.ArrayList;
	import java.util.List;
	import java.util.Random;
	import java.util.Vector;

	import org.apache.bcel.Constants;
	import org.apache.bcel.classfile.JavaClass;
	import org.apache.bcel.classfile.Method;
	import org.apache.bcel.generic.ConstantPoolGen;
	import org.apache.bcel.generic.GETFIELD;
	import org.apache.bcel.generic.InstructionHandle;
	import org.apache.bcel.generic.InvokeInstruction;
	import org.apache.bcel.generic.JsrInstruction;
	import org.apache.bcel.generic.LoadInstruction;
	import org.apache.bcel.generic.MethodGen;
	import org.apache.bcel.generic.ObjectType;
	import org.apache.bcel.generic.RET;
	import org.apache.bcel.generic.ReturnInstruction;
	import org.apache.bcel.generic.ReturnaddressType;
	import org.apache.bcel.generic.Type;
	import org.apache.bcel.verifier.PassVerifier;
	import org.apache.bcel.verifier.VerificationResult;
	import org.apache.bcel.verifier.exc.AssertionViolatedException;
	import org.apache.bcel.verifier.exc.StructuralCodeConstraintException;
	import org.apache.bcel.verifier.exc.VerifierConstraintViolatedException;

	/**
	* This PassVerifier verifies a method of class file according to pass 3,
	* so-called structural verification as described in The Java Virtual Machine
	* Specification, 2nd edition.
	* More detailed information is to be found at the do_verify() method's
	* documentation.
	*
	* @version $Id: ModifiedPass3bVerifier.java,v 1.3 2007-11-08 17:22:56 ebruneton Exp $
	* @author Enver Haase
	* @see #do_verify()
	*/

	public final class ModifiedPass3bVerifier extends PassVerifier{
	/* TODO: Throughout pass 3b, upper halves of LONG and DOUBLE
	are represented by Type.UNKNOWN. This should be changed
	in favour of LONG_Upper and DOUBLE_Upper as in pass 2. */

	/**
	* An InstructionContextQueue is a utility class that holds
	* (InstructionContext, ArrayList) pairs in a Queue data structure.
	* This is used to hold information about InstructionContext objects
	* externally --- i.e. that information is not saved inside the
	* InstructionContext object itself. This is useful to save the
	* execution path of the symbolic execution of the
	* Pass3bVerifier - this is not information
	* that belongs into the InstructionContext object itself.
	* Only at "execute()"ing
	* time, an InstructionContext object will get the current information
	* we have about its symbolic execution predecessors.
	*/
	static final class InstructionContextQueue{
	private List<InstructionContext> ics = new Vector<InstructionContext>(); // Type: InstructionContext
	private List<ArrayList<InstructionContext>> ecs = new Vector<ArrayList<InstructionContext>>(); // Type: ArrayList (of InstructionContext)
	public void add(InstructionContext ic, ArrayList<InstructionContext> executionChain){
	ics.add(ic);
	ecs.add(executionChain);
	}
	public boolean isEmpty(){
	return ics.isEmpty();
	}
	public void remove(){
	this.remove(0);
	}
	public void remove(int i){
	ics.remove(i);
	ecs.remove(i);
	}
	public InstructionContext getIC(int i){
	return ics.get(i);
	}
	public ArrayList<InstructionContext> getEC(int i){
	return ecs.get(i);
	}
	public int size(){
	return ics.size();
	}
	} // end Inner Class InstructionContextQueue

	/** In DEBUG mode, the verification algorithm is not randomized. */
	private static final boolean DEBUG = true;

	private JavaClass jc;

	/** The method number to verify. */
	private int method_no;

	/**
	* This class should only be instantiated by a Verifier.
	*
	* @see org.apache.bcel.verifier.Verifier
	*/
	public ModifiedPass3bVerifier(JavaClass jc, int method_no){
	this.jc = jc;
	this.method_no = method_no;
	}

	/**
	* Whenever the outgoing frame
	* situation of an InstructionContext changes, all its successors are
	* put [back] into the queue [as if they were unvisited].
	* The proof of termination is about the existence of a
	* fix point of frame merging.
	*/
	private void circulationPump(MethodGen m,ControlFlowGraph cfg, InstructionContext start, Frame vanillaFrame, InstConstraintVisitor icv, ExecutionVisitor ev){
	final Random random = new Random();
	InstructionContextQueue icq = new InstructionContextQueue();

	start.execute(vanillaFrame, new ArrayList<InstructionContext>(), icv, ev); // new ArrayList() <=> no Instruction was executed before
	// => Top-Level routine (no jsr call before)
	icq.add(start, new ArrayList<InstructionContext>());

	// LOOP!
	while (!icq.isEmpty()){
	InstructionContext u;
	ArrayList<InstructionContext> ec;
	if (!DEBUG){
	int r = random.nextInt(icq.size());
	u = icq.getIC(r);
	ec = icq.getEC(r);
	icq.remove(r);
	}
	else{
	u = icq.getIC(0);
	ec = icq.getEC(0);
	icq.remove(0);
	}

	ArrayList<InstructionContext> oldchain = new ArrayList<InstructionContext>(ec);
	ArrayList<InstructionContext> newchain = new ArrayList<InstructionContext>(ec);
	newchain.add(u);

	if ((u.getInstruction().getInstruction()) instanceof RET){
	//System.err.println(u);
	// We can only follow _one_ successor, the one after the
	// JSR that was recently executed.
	RET ret = (RET) (u.getInstruction().getInstruction());
	ReturnaddressType t = (ReturnaddressType) u.getOutFrame(oldchain).getLocals().get(ret.getIndex());
	InstructionContext theSuccessor = cfg.contextOf(t.getTarget());

	// Sanity check
	InstructionContext lastJSR = null;
	int skip_jsr = 0;
	for (int ss=oldchain.size()-1; ss >= 0; ss--){
	if (skip_jsr < 0){
	throw new AssertionViolatedException("More RET than JSR in execution chain?!");
	}
	//System.err.println("+"+oldchain.get(ss));
	if ((oldchain.get(ss)).getInstruction().getInstruction() instanceof JsrInstruction){
	if (skip_jsr == 0){
	lastJSR = oldchain.get(ss);
	break;
	}
	else{
	skip_jsr--;
	}
	}
	if ((oldchain.get(ss)).getInstruction().getInstruction() instanceof RET){
	skip_jsr++;
	}
	}
	if (lastJSR == null){
	throw new AssertionViolatedException("RET without a JSR before in ExecutionChain?! EC: '"+oldchain+"'.");
	}
	JsrInstruction jsr = (JsrInstruction) (lastJSR.getInstruction().getInstruction());
	if ( theSuccessor != (cfg.contextOf(jsr.physicalSuccessor())) ){
	throw new AssertionViolatedException("RET '"+u.getInstruction()+"' info inconsistent: jump back to '"+theSuccessor+"' or '"+cfg.contextOf(jsr.physicalSuccessor())+"'?");
	}

	if (theSuccessor.execute(u.getOutFrame(oldchain), newchain, icv, ev)){
	icq.add(theSuccessor, new ArrayList<InstructionContext> (newchain));
	}
	}
	else{// "not a ret"

	// Normal successors. Add them to the queue of successors.
	InstructionContext[] succs = u.getSuccessors();
	for (int s=0; s<succs.length; s++){
	InstructionContext v = succs[s];
	if (v.execute(u.getOutFrame(oldchain), newchain, icv, ev)){
	icq.add(v, new ArrayList<InstructionContext> (newchain));
	}
	}
	}// end "not a ret"

	// Exception Handlers. Add them to the queue of successors.
	// [subroutines are never protected; mandated by JustIce]
	ExceptionHandler[] exc_hds = u.getExceptionHandlers();
	for (int s=0; s<exc_hds.length; s++){
	InstructionContext v = cfg.contextOf(exc_hds[s].getHandlerStart());
	// TODO: the "oldchain" and "newchain" is used to determine the subroutine
	// we're in (by searching for the last JSR) by the InstructionContext
	// implementation. Therefore, we should not use this chain mechanism
	// when dealing with exception handlers.
	// Example: a JSR with an exception handler as its successor does not
	// mean we're in a subroutine if we go to the exception handler.
	// We should address this problem later; by now we simply "cut" the chain
	// by using an empty chain for the exception handlers.
	//if (v.execute(new Frame(u.getOutFrame(oldchain).getLocals(), new OperandStack (u.getOutFrame().getStack().maxStack(), (exc_hds[s].getExceptionType()==null? Type.THROWABLE : exc_hds[s].getExceptionType())) ), newchain), icv, ev){
	//icq.add(v, (ArrayList) newchain.clone());
	if (v.execute(new Frame(u.getOutFrame(oldchain).getLocals(), new OperandStack (u.getOutFrame(oldchain).getStack().maxStack(), (exc_hds[s].getExceptionType()==null? Type.THROWABLE : exc_hds[s].getExceptionType())) ), new ArrayList<InstructionContext>(), icv, ev)){
	icq.add(v, new ArrayList<InstructionContext>());
	}
	}

	}// while (!icq.isEmpty()) END

	InstructionHandle ih = start.getInstruction();
	do{
	if ((ih.getInstruction() instanceof ReturnInstruction) && (!(cfg.isDead(ih)))) {
	InstructionContext ic = cfg.contextOf(ih);
	Frame f = ic.getOutFrame(new ArrayList<InstructionContext>()); // TODO: This is buggy, we check only the top-level return instructions this way. Maybe some maniac returns from a method when in a subroutine?
	LocalVariables lvs = f.getLocals();
	for (int i=0; i<lvs.maxLocals(); i++){
	if (lvs.get(i) instanceof UninitializedObjectType){
	this.addMessage("Warning: ReturnInstruction '"+ic+"' may leave method with an uninitialized object in the local variables array '"+lvs+"'.");
	}
	}
	OperandStack os = f.getStack();
	for (int i=0; i<os.size(); i++){
	if (os.peek(i) instanceof UninitializedObjectType){
	this.addMessage("Warning: ReturnInstruction '"+ic+"' may leave method with an uninitialized object on the operand stack '"+os+"'.");
	}
	}
	//see JVM $4.8.2
	//TODO implement all based on stack
	Type returnedType = null;
	if( ih.getPrev().getInstruction() instanceof InvokeInstruction )
	{
	returnedType = ((InvokeInstruction)ih.getPrev().getInstruction()).getType(m.getConstantPool());
	}
	if( ih.getPrev().getInstruction() instanceof LoadInstruction )
	{
	int index = ((LoadInstruction)ih.getPrev().getInstruction()).getIndex();
	returnedType = lvs.get(index);
	}
	if( ih.getPrev().getInstruction() instanceof GETFIELD )
	{
	returnedType = ((GETFIELD)ih.getPrev().getInstruction()).getType(m.getConstantPool());
	}
	if( returnedType != null )
	{
	if( returnedType instanceof ObjectType )
	{
	try
	{
	if( !((ObjectType)returnedType).isAssignmentCompatibleWith(m.getReturnType()) )
	{
	throw new StructuralCodeConstraintException("Returned type "+returnedType+" does not match Method's return type "+m.getReturnType());
	}
	}
	catch (Exception e)
	{
	//dont know what do do now, so raise RuntimeException
	throw new RuntimeException(e);
	}
	}
	else if( !returnedType.equals(m.getReturnType()) )
	{
	throw new StructuralCodeConstraintException("Returned type "+returnedType+" does not match Method's return type "+m.getReturnType());
	}
	}
	}
	}while ((ih = ih.getNext()) != null);

	}

	/**
	* Pass 3b implements the data flow analysis as described in the Java Virtual
	* Machine Specification, Second Edition.
	* Later versions will use LocalVariablesInfo objects to verify if the
	* verifier-inferred types and the class file's debug information (LocalVariables
	* attributes) match [TODO].
	*
	* @see org.apache.bcel.verifier.statics.LocalVariablesInfo
	* @see org.apache.bcel.verifier.statics.Pass2Verifier#getLocalVariablesInfo(int)
	*/
	@Override
	public VerificationResult do_verify(){
	/*if (! myOwner.doPass3a(method_no).equals(VerificationResult.VR_OK)){
	return VerificationResult.VR_NOTYET;
	}

	// Pass 3a ran before, so it's safe to assume the JavaClass object is
	// in the BCEL repository.
	JavaClass jc;
	try {
	jc = Repository.lookupClass(myOwner.getClassName());
	} catch (ClassNotFoundException e) {
	// FIXME: maybe not the best way to handle this
	throw new AssertionViolatedException("Missing class: " + e.toString());
	}*/

	ConstantPoolGen constantPoolGen = new ConstantPoolGen(jc.getConstantPool());
	// Init Visitors
	InstConstraintVisitor icv = new InstConstraintVisitor();
	icv.setConstantPoolGen(constantPoolGen);

	ExecutionVisitor ev = new ExecutionVisitor();
	ev.setConstantPoolGen(constantPoolGen);

	Method[] methods = jc.getMethods(); // Method no "method_no" exists, we ran Pass3a before on it!

	try{

	MethodGen mg = new MethodGen(methods[method_no], jc.getClassName(), constantPoolGen);

	icv.setMethodGen(mg);

	////////////// DFA BEGINS HERE ////////////////
	if (! (mg.isAbstract() \|\| mg.isNative()) ){ // IF mg HAS CODE (See pass 2)

	ControlFlowGraph cfg = new ControlFlowGraph(mg);

	// Build the initial frame situation for this method.
	Frame f = new Frame(mg.getMaxLocals(),mg.getMaxStack());
	if ( !mg.isStatic() ){
	if (mg.getName().equals(Constants.CONSTRUCTOR_NAME)){
	Frame._this = new UninitializedObjectType(new ObjectType(jc.getClassName()));
	f.getLocals().set(0, Frame._this);
	}
	else{
	Frame._this = null;
	f.getLocals().set(0, new ObjectType(jc.getClassName()));
	}
	}
	Type[] argtypes = mg.getArgumentTypes();
	int twoslotoffset = 0;
	for (int j=0; j<argtypes.length; j++){
	if (argtypes[j] == Type.SHORT \|\| argtypes[j] == Type.BYTE \|\| argtypes[j] == Type.CHAR \|\| argtypes[j] == Type.BOOLEAN){
	argtypes[j] = Type.INT;
	}
	f.getLocals().set(twoslotoffset + j + (mg.isStatic()?0:1), argtypes[j]);
	if (argtypes[j].getSize() == 2){
	twoslotoffset++;
	f.getLocals().set(twoslotoffset + j + (mg.isStatic()?0:1), Type.UNKNOWN);
	}
	}
	circulationPump(mg,cfg, cfg.contextOf(mg.getInstructionList().getStart()), f, icv, ev);
	}
	}
	catch (VerifierConstraintViolatedException ce){
	ce.extendMessage("Constraint violated in method '"+methods[method_no]+"':\n","");
	return new VerificationResult(VerificationResult.VERIFIED_REJECTED, ce.getMessage());
	}
	catch (RuntimeException re){
	// These are internal errors

	StringWriter sw = new StringWriter();
	PrintWriter pw = new PrintWriter(sw);
	re.printStackTrace(pw);

	throw new AssertionViolatedException("Some RuntimeException occured while verify()ing class '"+jc.getClassName()+"', method '"+methods[method_no]+"'. Original RuntimeException's stack trace:\n---\n"+sw+"---\n");
	}
	return VerificationResult.VR_OK;
	}

	/** Returns the method number as supplied when instantiating. */
	public int getMethodNo(){
	return method_no;
	}
	}