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24 
25 #ifndef SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP
26 #define SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP
27 
28 #ifdef CHECK_UNHANDLED_OOPS
29 
30 // Detect unhanded oops in VM code
31 
32 // The design is that when an oop is declared on the stack as a local
33 // variable, the oop is actually a C++ struct with constructor and
34 // destructor.  The constructor adds the oop address on a list
35 // off each thread and the destructor removes the oop.  At a potential
36 // safepoint, the stack addresses of the local variable oops are trashed
37 // with a recognizable value.  If the local variable is used again, it
38 // will segfault, indicating an unsafe use of that oop.
39 // eg:
40 //    oop o;    //register &o on list
41 //    funct();  // if potential safepoint - causes clear_naked_oops()
42 //              // which trashes o above.
43 //    o->do_something();  // Crashes because o is unsafe.
44 //
45 // This code implements the details of the unhandled oop list on the thread.
46 //
47 
48 class oop;
49 class Thread;
50 
51 class UnhandledOopEntry : public CHeapObj<mtThread> {
52  friend class UnhandledOops;
53  private:
54   oop* _oop_ptr;
55   bool _ok_for_gc;
56   address _pc;
57  public:
oop_ptr()58   oop* oop_ptr() { return _oop_ptr; }
UnhandledOopEntry()59   UnhandledOopEntry() : _oop_ptr(NULL), _ok_for_gc(false), _pc(NULL) {}
UnhandledOopEntry(oop * op,address pc)60   UnhandledOopEntry(oop* op, address pc) :
61                         _oop_ptr(op),   _ok_for_gc(false), _pc(pc) {}
62 };
63 
64 
65 class UnhandledOops : public CHeapObj<mtThread> {
66  friend class Thread;
67  private:
68   Thread* _thread;
69   int _level;
70   GrowableArray<UnhandledOopEntry> *_oop_list;
71   void allow_unhandled_oop(oop* op);
72   void clear_unhandled_oops();
73   UnhandledOops(Thread* thread);
74   ~UnhandledOops();
75 
76  public:
77   static void dump_oops(UnhandledOops* list);
78   void register_unhandled_oop(oop* op, address pc);
79   void unregister_unhandled_oop(oop* op);
80 };
81 
82 #ifdef _LP64
83 const intptr_t BAD_OOP_ADDR =  0xfffffffffffffff1;
84 #else
85 const intptr_t BAD_OOP_ADDR =  0xfffffff1;
86 #endif // _LP64
87 #endif // CHECK_UNHANDLED_OOPS
88 
89 #endif // SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP
90