ReturnInstruction.java :  » Code-Analyzer » javapathfinder » gov » nasa » jpf » jvm » bytecode » Java Open Source

//
// Copyright (C) 2005 United States Government as represented by the
// Administrator of the National Aeronautics and Space Administration
// (NASA).  All Rights Reserved.
// 
// This software is distributed under the NASA Open Source Agreement
// (NOSA), version 1.3.  The NOSA has been approved by the Open Source
// Initiative.  See the file NOSA-1.3-JPF at the top of the distribution
// directory tree for the complete NOSA document.
// 
// THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF ANY
// KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT
// LIMITED TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO
// SPECIFICATIONS, ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR
// A PARTICULAR PURPOSE, OR FREEDOM FROM INFRINGEMENT, ANY WARRANTY THAT
// THE SUBJECT SOFTWARE WILL BE ERROR FREE, OR ANY WARRANTY THAT
// DOCUMENTATION, IF PROVIDED, WILL CONFORM TO THE SUBJECT SOFTWARE.
//
package gov.nasa.jpf.jvm.bytecode;

import gov.nasa.jpf.jvm.JVM;
import gov.nasa.jpf.jvm.MethodInfo;
import gov.nasa.jpf.jvm.ThreadInfo;

import org.apache.bcel.classfile.ConstantPool;
import org.apache.bcel.generic.InstructionHandle;


/**
 * abstraction for the various return instructions
 */
public abstract class ReturnInstruction extends Instruction {
  protected void init (InstructionHandle h, int o, MethodInfo m, 
                       ConstantPool cp) {
    super.init(h, o, m, cp);
    isObservable |= JVM.observableReturns.contains(mi.getCompleteName());
  }
  
  abstract int storeReturnValue (ThreadInfo th);
  abstract void pushReturnValue (ThreadInfo th);
  
  protected Instruction cleanUpAndAdvance (ThreadInfo th) {

    storeReturnValue(th);

    // always check if we have to unlock
    mi.leave(th);
    
    if (th.wasDirectCall()) {
      // return from something we called ourselves implicitly (i.e. there is
      // no corresponding invoke BC in the code)
      
      // there always has to be something on the stack, so we always have to remove
      // the args and return the pc that implicitly cause the direct call
      th.popFrame();
      th.removeArguments(mi);
      
      // we don't push any return value, since it wouldn't be used in the code
      return th.getPC();
    } else {    
      if (!th.popFrame()) {
        // no more frames, done with this thread (hence no need for a return value push)
        return null;
      } else {
        th.removeArguments(mi);
        pushReturnValue(th);
        
        return getNext(th);
      }
    }
  }
}