Java example source code file (unhandledOops.hpp)

This example Java source code file (unhandledOops.hpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bad_oop_addr, cheapobj, check_unhandled_oops, growablearray, share_vm_runtime_unhandledoops_hpp, thread, unhandledoopentry, unhandledoops

The unhandledOops.hpp Java example source code

/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP
#define SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP

#ifdef CHECK_UNHANDLED_OOPS

// Detect unhanded oops in VM code

// The design is that when an oop is declared on the stack as a local
// variable, the oop is actually a C++ struct with constructor and
// destructor.  The constructor adds the oop address on a list
// off each thread and the destructor removes the oop.  At a potential
// safepoint, the stack addresses of the local variable oops are trashed
// with a recognizeable value.  If the local variable is used again, it
// will segfault, indicating an unsafe use of that oop.
// eg:
//    oop o;    //register &o on list
//    funct();  // if potential safepoint - causes clear_naked_oops()
//              // which trashes o above.
//    o->do_something();  // Crashes because o is unsafe.
//
// This code implements the details of the unhandled oop list on the thread.
//

class oop;
class Thread;

class UnhandledOopEntry : public CHeapObj<mtThread> {
 friend class UnhandledOops;
 private:
  oop* _oop_ptr;
  bool _ok_for_gc;
  address _pc;
 public:
  oop* oop_ptr() { return _oop_ptr; }
  UnhandledOopEntry() : _oop_ptr(NULL), _ok_for_gc(false), _pc(NULL) {}
  UnhandledOopEntry(oop* op, address pc) :
                        _oop_ptr(op),   _ok_for_gc(false), _pc(pc) {}
};


class UnhandledOops : public CHeapObj<mtThread> {
 friend class Thread;
 private:
  Thread* _thread;
  int _level;
  GrowableArray<UnhandledOopEntry> *_oop_list;
  void allow_unhandled_oop(oop* op);
  void clear_unhandled_oops();
  UnhandledOops(Thread* thread);
  ~UnhandledOops();

 public:
  static void dump_oops(UnhandledOops* list);
  void register_unhandled_oop(oop* op, address pc);
  void unregister_unhandled_oop(oop* op);
};

#ifdef _LP64
const intptr_t BAD_OOP_ADDR =  0xfffffffffffffff1;
#else
const intptr_t BAD_OOP_ADDR =  0xfffffff1;
#endif // _LP64
#endif // CHECK_UNHANDLED_OOPS

#endif // SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP