src/main/java/org/apache/bcel/verifier/structurals/Pass3bVerifier.java - commons-bcel - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
  * The ASF licenses this file to You 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.Const;
 import org.apache.bcel.Repository;
 import org.apache.bcel.classfile.JavaClass;
 import org.apache.bcel.classfile.Method;
 import org.apache.bcel.generic.ConstantPoolGen;
 import org.apache.bcel.generic.InstructionHandle;
 import org.apache.bcel.generic.JsrInstruction;
 import org.apache.bcel.generic.MethodGen;
 import org.apache.bcel.generic.ObjectType;
 import org.apache.bcel.generic.RET;
 import org.apache.bcel.generic.ReferenceType;
 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.Verifier;
 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.
  *
  * @see #do_verify()
  */

 public final class Pass3bVerifier 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.
      */
     private static final class InstructionContextQueue {
         // The following two fields together represent the queue.
         /** The first elements from pairs in the queue. */
         private final List<InstructionContext> ics = new Vector<>();
         /** The second elements from pairs in the queue. */
         private final List<ArrayList<InstructionContext>> ecs = new Vector<>();

         /**
          * Adds an (InstructionContext, ExecutionChain) pair to this queue.
          *
          * @param ic the InstructionContext
          * @param executionChain the ExecutionChain
          */
         public void add(final InstructionContext ic, final ArrayList<InstructionContext> executionChain) {
             ics.add(ic);
             ecs.add(executionChain);
         }

         /**
          * Tests if InstructionContext queue is empty.
          *
          * @return true if the InstructionContext queue is empty.
          */
         public boolean isEmpty() {
             return ics.isEmpty();
         }

         /**
          * Removes a specific (InstructionContext, ExecutionChain) pair from their respective queues.
          *
          * @param i the index of the items to be removed
          */
         public void remove(final int i) {
             ics.remove(i);
             ecs.remove(i);
         }

         /**
          * Gets a specific InstructionContext from the queue.
          *
          * @param i the index of the item to be fetched
          * @return the indicated InstructionContext
          */
         public InstructionContext getIC(final int i) {
             return ics.get(i);
         }

         /**
          * Gets a specific ExecutionChain from the queue.
          *
          * @param i the index of the item to be fetched
          * @return the indicated ExecutionChain
          */
         public ArrayList<InstructionContext> getEC(final int i) {
             return ecs.get(i);
         }

         /**
          * Gets the size of the InstructionContext queue.
          *
          * @return the size of the InstructionQueue
          */
         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;

     /** The Verifier that created this. */
     private final Verifier myOwner;

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

     /**
      * This class should only be instantiated by a Verifier.
      *
      * @see org.apache.bcel.verifier.Verifier
      */
     public Pass3bVerifier(final Verifier owner, final int method_no) {
         myOwner = owner;
         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(final MethodGen m,final ControlFlowGraph cfg, final InstructionContext start,
             final Frame vanillaFrame, final InstConstraintVisitor icv, final ExecutionVisitor ev) {
         final Random random = new Random();
         final 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) {
                 final 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);
             }

             @SuppressWarnings("unchecked") // ec is of type ArrayList<InstructionContext>
             final
             ArrayList<InstructionContext> oldchain = (ArrayList<InstructionContext>) (ec.clone());
             @SuppressWarnings("unchecked") // ec is of type ArrayList<InstructionContext>
             final
             ArrayList<InstructionContext> newchain = (ArrayList<InstructionContext>) (ec.clone());
             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.
                 final RET ret = (RET) (u.getInstruction().getInstruction());
                 final ReturnaddressType t = (ReturnaddressType) u.getOutFrame(oldchain).getLocals().get(ret.getIndex());
                 final 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;
                         }
                         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+"'.");
                 }
                 final 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)) {
                     @SuppressWarnings("unchecked") // newchain is already of type ArrayList<InstructionContext>
                     final
                     ArrayList<InstructionContext> newchainClone = (ArrayList<InstructionContext>) newchain.clone();
                     icq.add(theSuccessor, newchainClone);
                 }
             }
             else{// "not a ret"

                 // Normal successors. Add them to the queue of successors.
                 final InstructionContext[] succs = u.getSuccessors();
                 for (final InstructionContext v : succs) {
                     if (v.execute(u.getOutFrame(oldchain), newchain, icv, ev)) {
                         @SuppressWarnings("unchecked") // newchain is already of type ArrayList<InstructionContext>
                         final
                         ArrayList<InstructionContext> newchainClone = (ArrayList<InstructionContext>) newchain.clone();
                         icq.add(v, newchainClone);
                     }
                 }
             }// end "not a ret"

             // Exception Handlers. Add them to the queue of successors.
             // [subroutines are never protected; mandated by JustIce]
             final ExceptionHandler[] exc_hds = u.getExceptionHandlers();
             for (final ExceptionHandler exc_hd : exc_hds) {
                 final InstructionContext v = cfg.contextOf(exc_hd.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_hd.getExceptionType()==null? Type.THROWABLE : exc_hd.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)))) {
                 final InstructionContext ic = cfg.contextOf(ih);
                 // 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?
                 final Frame f = ic.getOutFrame(new ArrayList<InstructionContext>());
                 final 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+"'.");
                     }
                 }
                 final 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
                 Type returnedType = null;
                 final OperandStack inStack = ic.getInFrame().getStack();
                 if (inStack.size() >= 1) {
                     returnedType = inStack.peek();
                 } else {
                     returnedType = Type.VOID;
                 }

                 if (returnedType != null) {
                     if (returnedType instanceof ReferenceType) {
                         try {
                             if (!((ReferenceType) returnedType).isCastableTo(m.getReturnType())) {
                                 invalidReturnTypeError(returnedType, m);
                             }
                         } catch (final ClassNotFoundException e) {
                             // Don't know what do do now, so raise RuntimeException
                             throw new RuntimeException(e);
                         }
                     } else if (!returnedType.equals(m.getReturnType().normalizeForStackOrLocal())) {
                         invalidReturnTypeError(returnedType, m);
                     }
                 }
             }
         } while ((ih = ih.getNext()) != null);

      }

     /**
      * Throws an exception indicating the returned type is not compatible with the return type of the given method.
      *
      * @param returnedType the type of the returned expression
      * @param m the method we are processing
      * @throws StructuralCodeConstraintException always
      * @since 6.0
      */
     public void invalidReturnTypeError(final Type returnedType, final MethodGen m) {
         throw new StructuralCodeConstraintException(
             "Returned type "+returnedType+" does not match Method's return type "+m.getReturnType());
     }

     /**
      * 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 (final ClassNotFoundException e) {
             // FIXME: maybe not the best way to handle this
             throw new AssertionViolatedException("Missing class: " + e, e);
         }

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

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

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

         try{

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

             icv.setMethodGen(mg);

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

                 final ControlFlowGraph cfg = new ControlFlowGraph(mg);

                 // Build the initial frame situation for this method.
                 final Frame f = new Frame(mg.getMaxLocals(),mg.getMaxStack());
                 if ( !mg.isStatic() ) {
                     if (mg.getName().equals(Const.CONSTRUCTOR_NAME)) {
                         Frame.setThis(new UninitializedObjectType(ObjectType.getInstance(jc.getClassName())));
                         f.getLocals().set(0, Frame.getThis());
                     }
                     else{
                         Frame.setThis(null);
                         f.getLocals().set(0, ObjectType.getInstance(jc.getClassName()));
                     }
                 }
                 final 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 (final VerifierConstraintViolatedException ce) {
             ce.extendMessage("Constraint violated in method '"+methods[method_no]+"':\n","");
             return new VerificationResult(VerificationResult.VERIFIED_REJECTED, ce.getMessage());
         }
         catch (final RuntimeException re) {
             // These are internal errors

             final StringWriter sw = new StringWriter();
             final 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", re);
         }
         return VerificationResult.VR_OK;
     }

     /** Returns the method number as supplied when instantiating. */
     public int getMethodNo() {
         return method_no;
     }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You 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.Const;
	import org.apache.bcel.Repository;
	import org.apache.bcel.classfile.JavaClass;
	import org.apache.bcel.classfile.Method;
	import org.apache.bcel.generic.ConstantPoolGen;
	import org.apache.bcel.generic.InstructionHandle;
	import org.apache.bcel.generic.JsrInstruction;
	import org.apache.bcel.generic.MethodGen;
	import org.apache.bcel.generic.ObjectType;
	import org.apache.bcel.generic.RET;
	import org.apache.bcel.generic.ReferenceType;
	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.Verifier;
	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.
	*
	* @see #do_verify()
	*/

	public final class Pass3bVerifier 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.
	*/
	private static final class InstructionContextQueue {
	// The following two fields together represent the queue.
	/** The first elements from pairs in the queue. */
	private final List<InstructionContext> ics = new Vector<>();
	/** The second elements from pairs in the queue. */
	private final List<ArrayList<InstructionContext>> ecs = new Vector<>();

	/**
	* Adds an (InstructionContext, ExecutionChain) pair to this queue.
	*
	* @param ic the InstructionContext
	* @param executionChain the ExecutionChain
	*/
	public void add(final InstructionContext ic, final ArrayList<InstructionContext> executionChain) {
	ics.add(ic);
	ecs.add(executionChain);
	}

	/**
	* Tests if InstructionContext queue is empty.
	*
	* @return true if the InstructionContext queue is empty.
	*/
	public boolean isEmpty() {
	return ics.isEmpty();
	}

	/**
	* Removes a specific (InstructionContext, ExecutionChain) pair from their respective queues.
	*
	* @param i the index of the items to be removed
	*/
	public void remove(final int i) {
	ics.remove(i);
	ecs.remove(i);
	}

	/**
	* Gets a specific InstructionContext from the queue.
	*
	* @param i the index of the item to be fetched
	* @return the indicated InstructionContext
	*/
	public InstructionContext getIC(final int i) {
	return ics.get(i);
	}

	/**
	* Gets a specific ExecutionChain from the queue.
	*
	* @param i the index of the item to be fetched
	* @return the indicated ExecutionChain
	*/
	public ArrayList<InstructionContext> getEC(final int i) {
	return ecs.get(i);
	}

	/**
	* Gets the size of the InstructionContext queue.
	*
	* @return the size of the InstructionQueue
	*/
	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;

	/** The Verifier that created this. */
	private final Verifier myOwner;

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

	/**
	* This class should only be instantiated by a Verifier.
	*
	* @see org.apache.bcel.verifier.Verifier
	*/
	public Pass3bVerifier(final Verifier owner, final int method_no) {
	myOwner = owner;
	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(final MethodGen m,final ControlFlowGraph cfg, final InstructionContext start,
	final Frame vanillaFrame, final InstConstraintVisitor icv, final ExecutionVisitor ev) {
	final Random random = new Random();
	final 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) {
	final 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);
	}

	@SuppressWarnings("unchecked") // ec is of type ArrayList<InstructionContext>
	final
	ArrayList<InstructionContext> oldchain = (ArrayList<InstructionContext>) (ec.clone());
	@SuppressWarnings("unchecked") // ec is of type ArrayList<InstructionContext>
	final
	ArrayList<InstructionContext> newchain = (ArrayList<InstructionContext>) (ec.clone());
	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.
	final RET ret = (RET) (u.getInstruction().getInstruction());
	final ReturnaddressType t = (ReturnaddressType) u.getOutFrame(oldchain).getLocals().get(ret.getIndex());
	final 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;
	}
	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+"'.");
	}
	final 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)) {
	@SuppressWarnings("unchecked") // newchain is already of type ArrayList<InstructionContext>
	final
	ArrayList<InstructionContext> newchainClone = (ArrayList<InstructionContext>) newchain.clone();
	icq.add(theSuccessor, newchainClone);
	}
	}
	else{// "not a ret"

	// Normal successors. Add them to the queue of successors.
	final InstructionContext[] succs = u.getSuccessors();
	for (final InstructionContext v : succs) {
	if (v.execute(u.getOutFrame(oldchain), newchain, icv, ev)) {
	@SuppressWarnings("unchecked") // newchain is already of type ArrayList<InstructionContext>
	final
	ArrayList<InstructionContext> newchainClone = (ArrayList<InstructionContext>) newchain.clone();
	icq.add(v, newchainClone);
	}
	}
	}// end "not a ret"

	// Exception Handlers. Add them to the queue of successors.
	// [subroutines are never protected; mandated by JustIce]
	final ExceptionHandler[] exc_hds = u.getExceptionHandlers();
	for (final ExceptionHandler exc_hd : exc_hds) {
	final InstructionContext v = cfg.contextOf(exc_hd.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_hd.getExceptionType()==null? Type.THROWABLE : exc_hd.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)))) {
	final InstructionContext ic = cfg.contextOf(ih);
	// 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?
	final Frame f = ic.getOutFrame(new ArrayList<InstructionContext>());
	final 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+"'.");
	}
	}
	final 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
	Type returnedType = null;
	final OperandStack inStack = ic.getInFrame().getStack();
	if (inStack.size() >= 1) {
	returnedType = inStack.peek();
	} else {
	returnedType = Type.VOID;
	}

	if (returnedType != null) {
	if (returnedType instanceof ReferenceType) {
	try {
	if (!((ReferenceType) returnedType).isCastableTo(m.getReturnType())) {
	invalidReturnTypeError(returnedType, m);
	}
	} catch (final ClassNotFoundException e) {
	// Don't know what do do now, so raise RuntimeException
	throw new RuntimeException(e);
	}
	} else if (!returnedType.equals(m.getReturnType().normalizeForStackOrLocal())) {
	invalidReturnTypeError(returnedType, m);
	}
	}
	}
	} while ((ih = ih.getNext()) != null);

	}

	/**
	* Throws an exception indicating the returned type is not compatible with the return type of the given method.
	*
	* @param returnedType the type of the returned expression
	* @param m the method we are processing
	* @throws StructuralCodeConstraintException always
	* @since 6.0
	*/
	public void invalidReturnTypeError(final Type returnedType, final MethodGen m) {
	throw new StructuralCodeConstraintException(
	"Returned type "+returnedType+" does not match Method's return type "+m.getReturnType());
	}

	/**
	* 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 (final ClassNotFoundException e) {
	// FIXME: maybe not the best way to handle this
	throw new AssertionViolatedException("Missing class: " + e, e);
	}

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

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

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

	try{

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

	icv.setMethodGen(mg);

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

	final ControlFlowGraph cfg = new ControlFlowGraph(mg);

	// Build the initial frame situation for this method.
	final Frame f = new Frame(mg.getMaxLocals(),mg.getMaxStack());
	if ( !mg.isStatic() ) {
	if (mg.getName().equals(Const.CONSTRUCTOR_NAME)) {
	Frame.setThis(new UninitializedObjectType(ObjectType.getInstance(jc.getClassName())));
	f.getLocals().set(0, Frame.getThis());
	}
	else{
	Frame.setThis(null);
	f.getLocals().set(0, ObjectType.getInstance(jc.getClassName()));
	}
	}
	final 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 (final VerifierConstraintViolatedException ce) {
	ce.extendMessage("Constraint violated in method '"+methods[method_no]+"':\n","");
	return new VerificationResult(VerificationResult.VERIFIED_REJECTED, ce.getMessage());
	}
	catch (final RuntimeException re) {
	// These are internal errors

	final StringWriter sw = new StringWriter();
	final 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", re);
	}
	return VerificationResult.VR_OK;
	}

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