src/share/vm/oops/instanceKlass.hpp

Wed, 17 Mar 2010 11:01:05 +0100

author
fparain
date
Wed, 17 Mar 2010 11:01:05 +0100
changeset 1759
e392695de029
parent 1590
4e6abf09f540
child 1907
c18cbe5936b8
permissions
-rw-r--r--

6935224: Adding new DTrace probes to work with Palantir
Summary: Adding probes related to thread scheduling and class initialization
Reviewed-by: kamg, never

     1 /*
     2  * Copyright 1997-2009 Sun Microsystems, Inc.  All Rights Reserved.
     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
     4  *
     5  * This code is free software; you can redistribute it and/or modify it
     6  * under the terms of the GNU General Public License version 2 only, as
     7  * published by the Free Software Foundation.
     8  *
     9  * This code is distributed in the hope that it will be useful, but WITHOUT
    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    12  * version 2 for more details (a copy is included in the LICENSE file that
    13  * accompanied this code).
    14  *
    15  * You should have received a copy of the GNU General Public License version
    16  * 2 along with this work; if not, write to the Free Software Foundation,
    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
    18  *
    19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
    20  * CA 95054 USA or visit www.sun.com if you need additional information or
    21  * have any questions.
    22  *
    23  */
    25 // An instanceKlass is the VM level representation of a Java class.
    26 // It contains all information needed for at class at execution runtime.
    28 //  instanceKlass layout:
    29 //    [header                     ] klassOop
    30 //    [klass pointer              ] klassOop
    31 //    [C++ vtbl pointer           ] Klass
    32 //    [subtype cache              ] Klass
    33 //    [instance size              ] Klass
    34 //    [java mirror                ] Klass
    35 //    [super                      ] Klass
    36 //    [access_flags               ] Klass
    37 //    [name                       ] Klass
    38 //    [first subklass             ] Klass
    39 //    [next sibling               ] Klass
    40 //    [array klasses              ]
    41 //    [methods                    ]
    42 //    [local interfaces           ]
    43 //    [transitive interfaces      ]
    44 //    [number of implementors     ]
    45 //    [implementors               ] klassOop[2]
    46 //    [fields                     ]
    47 //    [constants                  ]
    48 //    [class loader               ]
    49 //    [protection domain          ]
    50 //    [signers                    ]
    51 //    [source file name           ]
    52 //    [inner classes              ]
    53 //    [static field size          ]
    54 //    [nonstatic field size       ]
    55 //    [static oop fields size     ]
    56 //    [nonstatic oop maps size    ]
    57 //    [has finalize method        ]
    58 //    [deoptimization mark bit    ]
    59 //    [initialization state       ]
    60 //    [initializing thread        ]
    61 //    [Java vtable length         ]
    62 //    [oop map cache (stack maps) ]
    63 //    [EMBEDDED Java vtable             ] size in words = vtable_len
    64 //    [EMBEDDED static oop fields       ] size in words = static_oop_fields_size
    65 //    [         static non-oop fields   ] size in words = static_field_size - static_oop_fields_size
    66 //    [EMBEDDED nonstatic oop-map blocks] size in words = nonstatic_oop_map_size
    67 //
    68 //    The embedded nonstatic oop-map blocks are short pairs (offset, length) indicating
    69 //    where oops are located in instances of this klass.
    72 // forward declaration for class -- see below for definition
    73 class SuperTypeClosure;
    74 class JNIid;
    75 class jniIdMapBase;
    76 class BreakpointInfo;
    77 class fieldDescriptor;
    78 class DepChange;
    79 class nmethodBucket;
    80 class PreviousVersionNode;
    81 class JvmtiCachedClassFieldMap;
    83 // This is used in iterators below.
    84 class FieldClosure: public StackObj {
    85 public:
    86   virtual void do_field(fieldDescriptor* fd) = 0;
    87 };
    89 #ifndef PRODUCT
    90 // Print fields.
    91 // If "obj" argument to constructor is NULL, prints static fields, otherwise prints non-static fields.
    92 class FieldPrinter: public FieldClosure {
    93    oop _obj;
    94    outputStream* _st;
    95  public:
    96    FieldPrinter(outputStream* st, oop obj = NULL) : _obj(obj), _st(st) {}
    97    void do_field(fieldDescriptor* fd);
    98 };
    99 #endif  // !PRODUCT
   101 // ValueObjs embedded in klass. Describes where oops are located in instances of
   102 // this klass.
   103 class OopMapBlock VALUE_OBJ_CLASS_SPEC {
   104  public:
   105   // Byte offset of the first oop mapped by this block.
   106   int offset() const          { return _offset; }
   107   void set_offset(int offset) { _offset = offset; }
   109   // Number of oops in this block.
   110   uint count() const         { return _count; }
   111   void set_count(uint count) { _count = count; }
   113   // sizeof(OopMapBlock) in HeapWords.
   114   static const int size_in_words() {
   115     return align_size_up(int(sizeof(OopMapBlock)), HeapWordSize) >>
   116       LogHeapWordSize;
   117   }
   119  private:
   120   int  _offset;
   121   uint _count;
   122 };
   124 class instanceKlass: public Klass {
   125   friend class VMStructs;
   126  public:
   127   // See "The Java Virtual Machine Specification" section 2.16.2-5 for a detailed description
   128   // of the class loading & initialization procedure, and the use of the states.
   129   enum ClassState {
   130     unparsable_by_gc = 0,               // object is not yet parsable by gc. Value of _init_state at object allocation.
   131     allocated,                          // allocated (but not yet linked)
   132     loaded,                             // loaded and inserted in class hierarchy (but not linked yet)
   133     linked,                             // successfully linked/verified (but not initialized yet)
   134     being_initialized,                  // currently running class initializer
   135     fully_initialized,                  // initialized (successfull final state)
   136     initialization_error                // error happened during initialization
   137   };
   139  public:
   140   oop* oop_block_beg() const { return adr_array_klasses(); }
   141   oop* oop_block_end() const { return adr_methods_default_annotations() + 1; }
   143   enum {
   144     implementors_limit = 2              // how many implems can we track?
   145   };
   147  protected:
   148   //
   149   // The oop block.  See comment in klass.hpp before making changes.
   150   //
   152   // Array classes holding elements of this class.
   153   klassOop        _array_klasses;
   154   // Method array.
   155   objArrayOop     _methods;
   156   // Int array containing the original order of method in the class file (for
   157   // JVMTI).
   158   typeArrayOop    _method_ordering;
   159   // Interface (klassOops) this class declares locally to implement.
   160   objArrayOop     _local_interfaces;
   161   // Interface (klassOops) this class implements transitively.
   162   objArrayOop     _transitive_interfaces;
   163   // Instance and static variable information, 5-tuples of shorts [access, name
   164   // index, sig index, initval index, offset].
   165   typeArrayOop    _fields;
   166   // Constant pool for this class.
   167   constantPoolOop _constants;
   168   // Class loader used to load this class, NULL if VM loader used.
   169   oop             _class_loader;
   170   // Protection domain.
   171   oop             _protection_domain;
   172   // Host class, which grants its access privileges to this class also.
   173   // This is only non-null for an anonymous class (AnonymousClasses enabled).
   174   // The host class is either named, or a previously loaded anonymous class.
   175   klassOop        _host_klass;
   176   // Class signers.
   177   objArrayOop     _signers;
   178   // Name of source file containing this klass, NULL if not specified.
   179   symbolOop       _source_file_name;
   180   // the source debug extension for this klass, NULL if not specified.
   181   symbolOop       _source_debug_extension;
   182   // inner_classes attribute.
   183   typeArrayOop    _inner_classes;
   184   // Implementors of this interface (not valid if it overflows)
   185   klassOop        _implementors[implementors_limit];
   186   // Generic signature, or null if none.
   187   symbolOop       _generic_signature;
   188   // invokedynamic bootstrap method (a java.dyn.MethodHandle)
   189   oop             _bootstrap_method;
   190   // Annotations for this class, or null if none.
   191   typeArrayOop    _class_annotations;
   192   // Annotation objects (byte arrays) for fields, or null if no annotations.
   193   // Indices correspond to entries (not indices) in fields array.
   194   objArrayOop     _fields_annotations;
   195   // Annotation objects (byte arrays) for methods, or null if no annotations.
   196   // Index is the idnum, which is initially the same as the methods array index.
   197   objArrayOop     _methods_annotations;
   198   // Annotation objects (byte arrays) for methods' parameters, or null if no
   199   // such annotations.
   200   // Index is the idnum, which is initially the same as the methods array index.
   201   objArrayOop     _methods_parameter_annotations;
   202   // Annotation objects (byte arrays) for methods' default values, or null if no
   203   // such annotations.
   204   // Index is the idnum, which is initially the same as the methods array index.
   205   objArrayOop     _methods_default_annotations;
   207   //
   208   // End of the oop block.
   209   //
   211   // Number of heapOopSize words used by non-static fields in this klass
   212   // (including inherited fields but after header_size()).
   213   int             _nonstatic_field_size;
   214   int             _static_field_size;    // number words used by static fields (oop and non-oop) in this klass
   215   int             _static_oop_field_size;// number of static oop fields in this klass
   216   int             _nonstatic_oop_map_size;// size in words of nonstatic oop map blocks
   217   bool            _is_marked_dependent;  // used for marking during flushing and deoptimization
   218   bool            _rewritten;            // methods rewritten.
   219   bool            _has_nonstatic_fields; // for sizing with UseCompressedOops
   220   bool            _should_verify_class;  // allow caching of preverification
   221   u2              _minor_version;        // minor version number of class file
   222   u2              _major_version;        // major version number of class file
   223   ClassState      _init_state;           // state of class
   224   Thread*         _init_thread;          // Pointer to current thread doing initialization (to handle recusive initialization)
   225   int             _vtable_len;           // length of Java vtable (in words)
   226   int             _itable_len;           // length of Java itable (in words)
   227   ReferenceType   _reference_type;       // reference type
   228   OopMapCache*    volatile _oop_map_cache;   // OopMapCache for all methods in the klass (allocated lazily)
   229   JNIid*          _jni_ids;              // First JNI identifier for static fields in this class
   230   jmethodID*      _methods_jmethod_ids;  // jmethodIDs corresponding to method_idnum, or NULL if none
   231   int*            _methods_cached_itable_indices;  // itable_index cache for JNI invoke corresponding to methods idnum, or NULL
   232   nmethodBucket*  _dependencies;         // list of dependent nmethods
   233   nmethod*        _osr_nmethods_head;    // Head of list of on-stack replacement nmethods for this class
   234   BreakpointInfo* _breakpoints;          // bpt lists, managed by methodOop
   235   int             _nof_implementors;     // No of implementors of this interface (zero if not an interface)
   236   // Array of interesting part(s) of the previous version(s) of this
   237   // instanceKlass. See PreviousVersionWalker below.
   238   GrowableArray<PreviousVersionNode *>* _previous_versions;
   239   u2              _enclosing_method_class_index;  // Constant pool index for class of enclosing method, or 0 if none
   240   u2              _enclosing_method_method_index; // Constant pool index for name and type of enclosing method, or 0 if none
   241   // JVMTI fields can be moved to their own structure - see 6315920
   242   unsigned char * _cached_class_file_bytes;       // JVMTI: cached class file, before retransformable agent modified it in CFLH
   243   jint            _cached_class_file_len;         // JVMTI: length of above
   244   JvmtiCachedClassFieldMap* _jvmti_cached_class_field_map;  // JVMTI: used during heap iteration
   245   volatile u2     _idnum_allocated_count;         // JNI/JVMTI: increments with the addition of methods, old ids don't change
   247   // embedded Java vtable follows here
   248   // embedded Java itables follows here
   249   // embedded static fields follows here
   250   // embedded nonstatic oop-map blocks follows here
   252   friend class instanceKlassKlass;
   253   friend class SystemDictionary;
   255  public:
   256   bool has_nonstatic_fields() const        { return _has_nonstatic_fields; }
   257   void set_has_nonstatic_fields(bool b)    { _has_nonstatic_fields = b; }
   259   // field sizes
   260   int nonstatic_field_size() const         { return _nonstatic_field_size; }
   261   void set_nonstatic_field_size(int size)  { _nonstatic_field_size = size; }
   263   int static_field_size() const            { return _static_field_size; }
   264   void set_static_field_size(int size)     { _static_field_size = size; }
   266   int static_oop_field_size() const        { return _static_oop_field_size; }
   267   void set_static_oop_field_size(int size) { _static_oop_field_size = size; }
   269   // Java vtable
   270   int  vtable_length() const               { return _vtable_len; }
   271   void set_vtable_length(int len)          { _vtable_len = len; }
   273   // Java itable
   274   int  itable_length() const               { return _itable_len; }
   275   void set_itable_length(int len)          { _itable_len = len; }
   277   // array klasses
   278   klassOop array_klasses() const           { return _array_klasses; }
   279   void set_array_klasses(klassOop k)       { oop_store_without_check((oop*) &_array_klasses, (oop) k); }
   281   // methods
   282   objArrayOop methods() const              { return _methods; }
   283   void set_methods(objArrayOop a)          { oop_store_without_check((oop*) &_methods, (oop) a); }
   284   methodOop method_with_idnum(int idnum);
   286   // method ordering
   287   typeArrayOop method_ordering() const     { return _method_ordering; }
   288   void set_method_ordering(typeArrayOop m) { oop_store_without_check((oop*) &_method_ordering, (oop) m); }
   290   // interfaces
   291   objArrayOop local_interfaces() const          { return _local_interfaces; }
   292   void set_local_interfaces(objArrayOop a)      { oop_store_without_check((oop*) &_local_interfaces, (oop) a); }
   293   objArrayOop transitive_interfaces() const     { return _transitive_interfaces; }
   294   void set_transitive_interfaces(objArrayOop a) { oop_store_without_check((oop*) &_transitive_interfaces, (oop) a); }
   296   // fields
   297   // Field info extracted from the class file and stored
   298   // as an array of 7 shorts
   299   enum FieldOffset {
   300     access_flags_offset    = 0,
   301     name_index_offset      = 1,
   302     signature_index_offset = 2,
   303     initval_index_offset   = 3,
   304     low_offset             = 4,
   305     high_offset            = 5,
   306     generic_signature_offset = 6,
   307     next_offset            = 7
   308   };
   310   typeArrayOop fields() const              { return _fields; }
   311   int offset_from_fields( int index ) const {
   312     return build_int_from_shorts( fields()->ushort_at(index + low_offset),
   313                                   fields()->ushort_at(index + high_offset) );
   314   }
   316   void set_fields(typeArrayOop f)          { oop_store_without_check((oop*) &_fields, (oop) f); }
   318   // inner classes
   319   typeArrayOop inner_classes() const       { return _inner_classes; }
   320   void set_inner_classes(typeArrayOop f)   { oop_store_without_check((oop*) &_inner_classes, (oop) f); }
   322   enum InnerClassAttributeOffset {
   323     // From http://mirror.eng/products/jdk/1.1/docs/guide/innerclasses/spec/innerclasses.doc10.html#18814
   324     inner_class_inner_class_info_offset = 0,
   325     inner_class_outer_class_info_offset = 1,
   326     inner_class_inner_name_offset = 2,
   327     inner_class_access_flags_offset = 3,
   328     inner_class_next_offset = 4
   329   };
   331   // method override check
   332   bool is_override(methodHandle super_method, Handle targetclassloader, symbolHandle targetclassname, TRAPS);
   334   // package
   335   bool is_same_class_package(klassOop class2);
   336   bool is_same_class_package(oop classloader2, symbolOop classname2);
   337   static bool is_same_class_package(oop class_loader1, symbolOop class_name1, oop class_loader2, symbolOop class_name2);
   339   // find an enclosing class (defined where original code was, in jvm.cpp!)
   340   klassOop compute_enclosing_class(bool* inner_is_member, TRAPS) {
   341     instanceKlassHandle self(THREAD, this->as_klassOop());
   342     return compute_enclosing_class_impl(self, inner_is_member, THREAD);
   343   }
   344   static klassOop compute_enclosing_class_impl(instanceKlassHandle self,
   345                                                bool* inner_is_member, TRAPS);
   347   // tell if two classes have the same enclosing class (at package level)
   348   bool is_same_package_member(klassOop class2, TRAPS) {
   349     instanceKlassHandle self(THREAD, this->as_klassOop());
   350     return is_same_package_member_impl(self, class2, THREAD);
   351   }
   352   static bool is_same_package_member_impl(instanceKlassHandle self,
   353                                           klassOop class2, TRAPS);
   355   // initialization state
   356   bool is_loaded() const                   { return _init_state >= loaded; }
   357   bool is_linked() const                   { return _init_state >= linked; }
   358   bool is_initialized() const              { return _init_state == fully_initialized; }
   359   bool is_not_initialized() const          { return _init_state <  being_initialized; }
   360   bool is_being_initialized() const        { return _init_state == being_initialized; }
   361   bool is_in_error_state() const           { return _init_state == initialization_error; }
   362   bool is_reentrant_initialization(Thread *thread)  { return thread == _init_thread; }
   363   int  get_init_state()                    { return _init_state; } // Useful for debugging
   364   bool is_rewritten() const                { return _rewritten; }
   366   // defineClass specified verification
   367   bool should_verify_class() const         { return _should_verify_class; }
   368   void set_should_verify_class(bool value) { _should_verify_class = value; }
   370   // marking
   371   bool is_marked_dependent() const         { return _is_marked_dependent; }
   372   void set_is_marked_dependent(bool value) { _is_marked_dependent = value; }
   374   // initialization (virtuals from Klass)
   375   bool should_be_initialized() const;  // means that initialize should be called
   376   void initialize(TRAPS);
   377   void link_class(TRAPS);
   378   bool link_class_or_fail(TRAPS); // returns false on failure
   379   void unlink_class();
   380   void rewrite_class(TRAPS);
   381   methodOop class_initializer();
   383   // set the class to initialized if no static initializer is present
   384   void eager_initialize(Thread *thread);
   386   // reference type
   387   ReferenceType reference_type() const     { return _reference_type; }
   388   void set_reference_type(ReferenceType t) { _reference_type = t; }
   390   // find local field, returns true if found
   391   bool find_local_field(symbolOop name, symbolOop sig, fieldDescriptor* fd) const;
   392   // find field in direct superinterfaces, returns the interface in which the field is defined
   393   klassOop find_interface_field(symbolOop name, symbolOop sig, fieldDescriptor* fd) const;
   394   // find field according to JVM spec 5.4.3.2, returns the klass in which the field is defined
   395   klassOop find_field(symbolOop name, symbolOop sig, fieldDescriptor* fd) const;
   396   // find instance or static fields according to JVM spec 5.4.3.2, returns the klass in which the field is defined
   397   klassOop find_field(symbolOop name, symbolOop sig, bool is_static, fieldDescriptor* fd) const;
   399   // find a non-static or static field given its offset within the class.
   400   bool contains_field_offset(int offset) {
   401     return instanceOopDesc::contains_field_offset(offset, nonstatic_field_size());
   402   }
   404   bool find_local_field_from_offset(int offset, bool is_static, fieldDescriptor* fd) const;
   405   bool find_field_from_offset(int offset, bool is_static, fieldDescriptor* fd) const;
   407   // find a local method (returns NULL if not found)
   408   methodOop find_method(symbolOop name, symbolOop signature) const;
   409   static methodOop find_method(objArrayOop methods, symbolOop name, symbolOop signature);
   411   // lookup operation (returns NULL if not found)
   412   methodOop uncached_lookup_method(symbolOop name, symbolOop signature) const;
   414   // lookup a method in all the interfaces that this class implements
   415   // (returns NULL if not found)
   416   methodOop lookup_method_in_all_interfaces(symbolOop name, symbolOop signature) const;
   418   // constant pool
   419   constantPoolOop constants() const        { return _constants; }
   420   void set_constants(constantPoolOop c)    { oop_store_without_check((oop*) &_constants, (oop) c); }
   422   // class loader
   423   oop class_loader() const                 { return _class_loader; }
   424   void set_class_loader(oop l)             { oop_store((oop*) &_class_loader, l); }
   426   // protection domain
   427   oop protection_domain()                  { return _protection_domain; }
   428   void set_protection_domain(oop pd)       { oop_store((oop*) &_protection_domain, pd); }
   430   // host class
   431   oop host_klass() const                   { return _host_klass; }
   432   void set_host_klass(oop host)            { oop_store((oop*) &_host_klass, host); }
   433   bool is_anonymous() const                { return _host_klass != NULL; }
   435   // signers
   436   objArrayOop signers() const              { return _signers; }
   437   void set_signers(objArrayOop s)          { oop_store((oop*) &_signers, oop(s)); }
   439   // source file name
   440   symbolOop source_file_name() const       { return _source_file_name; }
   441   void set_source_file_name(symbolOop n)   { oop_store_without_check((oop*) &_source_file_name, (oop) n); }
   443   // minor and major version numbers of class file
   444   u2 minor_version() const                 { return _minor_version; }
   445   void set_minor_version(u2 minor_version) { _minor_version = minor_version; }
   446   u2 major_version() const                 { return _major_version; }
   447   void set_major_version(u2 major_version) { _major_version = major_version; }
   449   // source debug extension
   450   symbolOop source_debug_extension() const    { return _source_debug_extension; }
   451   void set_source_debug_extension(symbolOop n){ oop_store_without_check((oop*) &_source_debug_extension, (oop) n); }
   453   // nonstatic oop-map blocks
   454   static int nonstatic_oop_map_size(unsigned int oop_map_count) {
   455     return oop_map_count * OopMapBlock::size_in_words();
   456   }
   457   unsigned int nonstatic_oop_map_count() const {
   458     return _nonstatic_oop_map_size / OopMapBlock::size_in_words();
   459   }
   460   int nonstatic_oop_map_size() const { return _nonstatic_oop_map_size; }
   461   void set_nonstatic_oop_map_size(int words) {
   462     _nonstatic_oop_map_size = words;
   463   }
   465   // RedefineClasses() support for previous versions:
   466   void add_previous_version(instanceKlassHandle ikh, BitMap *emcp_methods,
   467          int emcp_method_count);
   468   // If the _previous_versions array is non-NULL, then this klass
   469   // has been redefined at least once even if we aren't currently
   470   // tracking a previous version.
   471   bool has_been_redefined() const { return _previous_versions != NULL; }
   472   bool has_previous_version() const;
   473   void init_previous_versions() {
   474     _previous_versions = NULL;
   475   }
   476   GrowableArray<PreviousVersionNode *>* previous_versions() const {
   477     return _previous_versions;
   478   }
   480   // JVMTI: Support for caching a class file before it is modified by an agent that can do retransformation
   481   void set_cached_class_file(unsigned char *class_file_bytes,
   482                              jint class_file_len)     { _cached_class_file_len = class_file_len;
   483                                                         _cached_class_file_bytes = class_file_bytes; }
   484   jint get_cached_class_file_len()                    { return _cached_class_file_len; }
   485   unsigned char * get_cached_class_file_bytes()       { return _cached_class_file_bytes; }
   487   // JVMTI: Support for caching of field indices, types, and offsets
   488   void set_jvmti_cached_class_field_map(JvmtiCachedClassFieldMap* descriptor) {
   489     _jvmti_cached_class_field_map = descriptor;
   490   }
   491   JvmtiCachedClassFieldMap* jvmti_cached_class_field_map() const {
   492     return _jvmti_cached_class_field_map;
   493   }
   495   // for adding methods, constMethodOopDesc::UNSET_IDNUM means no more ids available
   496   inline u2 next_method_idnum();
   497   void set_initial_method_idnum(u2 value)             { _idnum_allocated_count = value; }
   499   // generics support
   500   symbolOop generic_signature() const                 { return _generic_signature; }
   501   void set_generic_signature(symbolOop sig)           { oop_store_without_check((oop*)&_generic_signature, (oop)sig); }
   502   u2 enclosing_method_class_index() const             { return _enclosing_method_class_index; }
   503   u2 enclosing_method_method_index() const            { return _enclosing_method_method_index; }
   504   void set_enclosing_method_indices(u2 class_index,
   505                                     u2 method_index)  { _enclosing_method_class_index  = class_index;
   506                                                         _enclosing_method_method_index = method_index; }
   508   // JSR 292 support
   509   oop bootstrap_method() const                        { return _bootstrap_method; }
   510   void set_bootstrap_method(oop mh)                   { oop_store(&_bootstrap_method, mh); }
   512   // jmethodID support
   513   static jmethodID get_jmethod_id(instanceKlassHandle ik_h,
   514                      methodHandle method_h);
   515   static jmethodID get_jmethod_id_fetch_or_update(instanceKlassHandle ik_h,
   516                      size_t idnum, jmethodID new_id, jmethodID* new_jmeths,
   517                      jmethodID* to_dealloc_id_p,
   518                      jmethodID** to_dealloc_jmeths_p);
   519   static void get_jmethod_id_length_value(jmethodID* cache, size_t idnum,
   520                 size_t *length_p, jmethodID* id_p);
   521   jmethodID jmethod_id_or_null(methodOop method);
   523   // cached itable index support
   524   void set_cached_itable_index(size_t idnum, int index);
   525   int cached_itable_index(size_t idnum);
   527   // annotations support
   528   typeArrayOop class_annotations() const              { return _class_annotations; }
   529   objArrayOop fields_annotations() const              { return _fields_annotations; }
   530   objArrayOop methods_annotations() const             { return _methods_annotations; }
   531   objArrayOop methods_parameter_annotations() const   { return _methods_parameter_annotations; }
   532   objArrayOop methods_default_annotations() const     { return _methods_default_annotations; }
   533   void set_class_annotations(typeArrayOop md)            { oop_store_without_check((oop*)&_class_annotations, (oop)md); }
   534   void set_fields_annotations(objArrayOop md)            { set_annotations(md, &_fields_annotations); }
   535   void set_methods_annotations(objArrayOop md)           { set_annotations(md, &_methods_annotations); }
   536   void set_methods_parameter_annotations(objArrayOop md) { set_annotations(md, &_methods_parameter_annotations); }
   537   void set_methods_default_annotations(objArrayOop md)   { set_annotations(md, &_methods_default_annotations); }
   538   typeArrayOop get_method_annotations_of(int idnum)
   539                                                 { return get_method_annotations_from(idnum, _methods_annotations); }
   540   typeArrayOop get_method_parameter_annotations_of(int idnum)
   541                                                 { return get_method_annotations_from(idnum, _methods_parameter_annotations); }
   542   typeArrayOop get_method_default_annotations_of(int idnum)
   543                                                 { return get_method_annotations_from(idnum, _methods_default_annotations); }
   544   void set_method_annotations_of(int idnum, typeArrayOop anno)
   545                                                 { set_methods_annotations_of(idnum, anno, &_methods_annotations); }
   546   void set_method_parameter_annotations_of(int idnum, typeArrayOop anno)
   547                                                 { set_methods_annotations_of(idnum, anno, &_methods_annotations); }
   548   void set_method_default_annotations_of(int idnum, typeArrayOop anno)
   549                                                 { set_methods_annotations_of(idnum, anno, &_methods_annotations); }
   551   // allocation
   552   DEFINE_ALLOCATE_PERMANENT(instanceKlass);
   553   instanceOop allocate_instance(TRAPS);
   554   instanceOop allocate_permanent_instance(TRAPS);
   556   // additional member function to return a handle
   557   instanceHandle allocate_instance_handle(TRAPS)      { return instanceHandle(THREAD, allocate_instance(THREAD)); }
   559   objArrayOop allocate_objArray(int n, int length, TRAPS);
   560   // Helper function
   561   static instanceOop register_finalizer(instanceOop i, TRAPS);
   563   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
   564   // if not, throw either an Error or an Exception.
   565   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
   567   // initialization
   568   void call_class_initializer(TRAPS);
   569   void set_initialization_state_and_notify(ClassState state, TRAPS);
   571   // OopMapCache support
   572   OopMapCache* oop_map_cache()               { return _oop_map_cache; }
   573   void set_oop_map_cache(OopMapCache *cache) { _oop_map_cache = cache; }
   574   void mask_for(methodHandle method, int bci, InterpreterOopMap* entry);
   576   // JNI identifier support (for static fields - for jni performance)
   577   JNIid* jni_ids()                               { return _jni_ids; }
   578   void set_jni_ids(JNIid* ids)                   { _jni_ids = ids; }
   579   JNIid* jni_id_for(int offset);
   581   // maintenance of deoptimization dependencies
   582   int mark_dependent_nmethods(DepChange& changes);
   583   void add_dependent_nmethod(nmethod* nm);
   584   void remove_dependent_nmethod(nmethod* nm);
   586   // On-stack replacement support
   587   nmethod* osr_nmethods_head() const         { return _osr_nmethods_head; };
   588   void set_osr_nmethods_head(nmethod* h)     { _osr_nmethods_head = h; };
   589   void add_osr_nmethod(nmethod* n);
   590   void remove_osr_nmethod(nmethod* n);
   591   nmethod* lookup_osr_nmethod(const methodOop m, int bci) const;
   593   // Breakpoint support (see methods on methodOop for details)
   594   BreakpointInfo* breakpoints() const       { return _breakpoints; };
   595   void set_breakpoints(BreakpointInfo* bps) { _breakpoints = bps; };
   597   // support for stub routines
   598   static int init_state_offset_in_bytes()    { return offset_of(instanceKlass, _init_state); }
   599   static int init_thread_offset_in_bytes()   { return offset_of(instanceKlass, _init_thread); }
   601   // subclass/subinterface checks
   602   bool implements_interface(klassOop k) const;
   604   // Access to implementors of an interface. We only store the count
   605   // of implementors, and in case, there are only a few
   606   // implementors, we store them in a short list.
   607   // This accessor returns NULL if we walk off the end of the list.
   608   klassOop implementor(int i) const {
   609     return (i < implementors_limit)? _implementors[i]: (klassOop) NULL;
   610   }
   611   int  nof_implementors() const       { return _nof_implementors; }
   612   void add_implementor(klassOop k);  // k is a new class that implements this interface
   613   void init_implementor();           // initialize
   615   // link this class into the implementors list of every interface it implements
   616   void process_interfaces(Thread *thread);
   618   // virtual operations from Klass
   619   bool is_leaf_class() const               { return _subklass == NULL; }
   620   objArrayOop compute_secondary_supers(int num_extra_slots, TRAPS);
   621   bool compute_is_subtype_of(klassOop k);
   622   bool can_be_primary_super_slow() const;
   623   klassOop java_super() const              { return super(); }
   624   int oop_size(oop obj)  const             { return size_helper(); }
   625   int klass_oop_size() const               { return object_size(); }
   626   bool oop_is_instance_slow() const        { return true; }
   628   // Iterators
   629   void do_local_static_fields(FieldClosure* cl);
   630   void do_nonstatic_fields(FieldClosure* cl); // including inherited fields
   631   void do_local_static_fields(void f(fieldDescriptor*, TRAPS), TRAPS);
   633   void methods_do(void f(methodOop method));
   634   void array_klasses_do(void f(klassOop k));
   635   void with_array_klasses_do(void f(klassOop k));
   636   bool super_types_do(SuperTypeClosure* blk);
   638   // Casting from klassOop
   639   static instanceKlass* cast(klassOop k) {
   640     Klass* kp = k->klass_part();
   641     assert(kp->null_vtbl() || kp->oop_is_instance_slow(), "cast to instanceKlass");
   642     return (instanceKlass*) kp;
   643   }
   645   // Sizing (in words)
   646   static int header_size()            { return align_object_offset(oopDesc::header_size() + sizeof(instanceKlass)/HeapWordSize); }
   647   int object_size() const             { return object_size(align_object_offset(vtable_length()) + align_object_offset(itable_length()) + static_field_size() + nonstatic_oop_map_size()); }
   648   static int vtable_start_offset()    { return header_size(); }
   649   static int vtable_length_offset()   { return oopDesc::header_size() + offset_of(instanceKlass, _vtable_len) / HeapWordSize; }
   650   static int object_size(int extra)   { return align_object_size(header_size() + extra); }
   652   intptr_t* start_of_vtable() const        { return ((intptr_t*)as_klassOop()) + vtable_start_offset(); }
   653   intptr_t* start_of_itable() const        { return start_of_vtable() + align_object_offset(vtable_length()); }
   654   int  itable_offset_in_words() const { return start_of_itable() - (intptr_t*)as_klassOop(); }
   656   // Static field offset is an offset into the Heap, should be converted by
   657   // based on UseCompressedOop for traversal
   658   HeapWord* start_of_static_fields() const {
   659     return (HeapWord*)(start_of_itable() + align_object_offset(itable_length()));
   660   }
   662   intptr_t* end_of_itable() const          { return start_of_itable() + itable_length(); }
   664   int offset_of_static_fields() const {
   665     return (intptr_t)start_of_static_fields() - (intptr_t)as_klassOop();
   666   }
   668   OopMapBlock* start_of_nonstatic_oop_maps() const {
   669     return (OopMapBlock*) (start_of_static_fields() + static_field_size());
   670   }
   672   // Allocation profiling support
   673   juint alloc_size() const            { return _alloc_count * size_helper(); }
   674   void set_alloc_size(juint n)        {}
   676   // Use this to return the size of an instance in heap words:
   677   int size_helper() const {
   678     return layout_helper_to_size_helper(layout_helper());
   679   }
   681   // This bit is initialized in classFileParser.cpp.
   682   // It is false under any of the following conditions:
   683   //  - the class is abstract (including any interface)
   684   //  - the class has a finalizer (if !RegisterFinalizersAtInit)
   685   //  - the class size is larger than FastAllocateSizeLimit
   686   //  - the class is java/lang/Class, which cannot be allocated directly
   687   bool can_be_fastpath_allocated() const {
   688     return !layout_helper_needs_slow_path(layout_helper());
   689   }
   691   // Java vtable/itable
   692   klassVtable* vtable() const;        // return new klassVtable wrapper
   693   inline methodOop method_at_vtable(int index);
   694   klassItable* itable() const;        // return new klassItable wrapper
   695   methodOop method_at_itable(klassOop holder, int index, TRAPS);
   697   // Garbage collection
   698   void oop_follow_contents(oop obj);
   699   void follow_static_fields();
   700   void adjust_static_fields();
   701   int  oop_adjust_pointers(oop obj);
   702   bool object_is_parsable() const { return _init_state != unparsable_by_gc; }
   703        // Value of _init_state must be zero (unparsable_by_gc) when klass field is set.
   705   void follow_weak_klass_links(
   706     BoolObjectClosure* is_alive, OopClosure* keep_alive);
   707   void release_C_heap_structures();
   709   // Parallel Scavenge and Parallel Old
   710   PARALLEL_GC_DECLS
   712 #ifndef SERIALGC
   713   // Parallel Scavenge
   714   void copy_static_fields(PSPromotionManager* pm);
   715   void push_static_fields(PSPromotionManager* pm);
   717   // Parallel Old
   718   void follow_static_fields(ParCompactionManager* cm);
   719   void copy_static_fields(ParCompactionManager* cm);
   720   void update_static_fields();
   721   void update_static_fields(HeapWord* beg_addr, HeapWord* end_addr);
   722 #endif // SERIALGC
   724   // Naming
   725   const char* signature_name() const;
   727   // Iterators
   728   int oop_oop_iterate(oop obj, OopClosure* blk) {
   729     return oop_oop_iterate_v(obj, blk);
   730   }
   732   int oop_oop_iterate_m(oop obj, OopClosure* blk, MemRegion mr) {
   733     return oop_oop_iterate_v_m(obj, blk, mr);
   734   }
   736 #define InstanceKlass_OOP_OOP_ITERATE_DECL(OopClosureType, nv_suffix)      \
   737   int  oop_oop_iterate##nv_suffix(oop obj, OopClosureType* blk);           \
   738   int  oop_oop_iterate##nv_suffix##_m(oop obj, OopClosureType* blk,        \
   739                                       MemRegion mr);
   741   ALL_OOP_OOP_ITERATE_CLOSURES_1(InstanceKlass_OOP_OOP_ITERATE_DECL)
   742   ALL_OOP_OOP_ITERATE_CLOSURES_2(InstanceKlass_OOP_OOP_ITERATE_DECL)
   744 #ifndef SERIALGC
   745 #define InstanceKlass_OOP_OOP_ITERATE_BACKWARDS_DECL(OopClosureType, nv_suffix) \
   746   int  oop_oop_iterate_backwards##nv_suffix(oop obj, OopClosureType* blk);
   748   ALL_OOP_OOP_ITERATE_CLOSURES_1(InstanceKlass_OOP_OOP_ITERATE_BACKWARDS_DECL)
   749   ALL_OOP_OOP_ITERATE_CLOSURES_2(InstanceKlass_OOP_OOP_ITERATE_BACKWARDS_DECL)
   750 #endif // !SERIALGC
   752   void iterate_static_fields(OopClosure* closure);
   753   void iterate_static_fields(OopClosure* closure, MemRegion mr);
   755 private:
   756   // initialization state
   757 #ifdef ASSERT
   758   void set_init_state(ClassState state);
   759 #else
   760   void set_init_state(ClassState state) { _init_state = state; }
   761 #endif
   762   void set_rewritten()                  { _rewritten = true; }
   763   void set_init_thread(Thread *thread)  { _init_thread = thread; }
   765   u2 idnum_allocated_count() const      { return _idnum_allocated_count; }
   766   // The RedefineClasses() API can cause new method idnums to be needed
   767   // which will cause the caches to grow. Safety requires different
   768   // cache management logic if the caches can grow instead of just
   769   // going from NULL to non-NULL.
   770   bool idnum_can_increment() const      { return has_been_redefined(); }
   771   jmethodID* methods_jmethod_ids_acquire() const
   772          { return (jmethodID*)OrderAccess::load_ptr_acquire(&_methods_jmethod_ids); }
   773   void release_set_methods_jmethod_ids(jmethodID* jmeths)
   774          { OrderAccess::release_store_ptr(&_methods_jmethod_ids, jmeths); }
   776   int* methods_cached_itable_indices_acquire() const
   777          { return (int*)OrderAccess::load_ptr_acquire(&_methods_cached_itable_indices); }
   778   void release_set_methods_cached_itable_indices(int* indices)
   779          { OrderAccess::release_store_ptr(&_methods_cached_itable_indices, indices); }
   781   inline typeArrayOop get_method_annotations_from(int idnum, objArrayOop annos);
   782   void set_annotations(objArrayOop md, objArrayOop* md_p)  { oop_store_without_check((oop*)md_p, (oop)md); }
   783   void set_methods_annotations_of(int idnum, typeArrayOop anno, objArrayOop* md_p);
   785   // Offsets for memory management
   786   oop* adr_array_klasses() const     { return (oop*)&this->_array_klasses;}
   787   oop* adr_methods() const           { return (oop*)&this->_methods;}
   788   oop* adr_method_ordering() const   { return (oop*)&this->_method_ordering;}
   789   oop* adr_local_interfaces() const  { return (oop*)&this->_local_interfaces;}
   790   oop* adr_transitive_interfaces() const  { return (oop*)&this->_transitive_interfaces;}
   791   oop* adr_fields() const            { return (oop*)&this->_fields;}
   792   oop* adr_constants() const         { return (oop*)&this->_constants;}
   793   oop* adr_class_loader() const      { return (oop*)&this->_class_loader;}
   794   oop* adr_protection_domain() const { return (oop*)&this->_protection_domain;}
   795   oop* adr_host_klass() const        { return (oop*)&this->_host_klass;}
   796   oop* adr_signers() const           { return (oop*)&this->_signers;}
   797   oop* adr_source_file_name() const  { return (oop*)&this->_source_file_name;}
   798   oop* adr_source_debug_extension() const { return (oop*)&this->_source_debug_extension;}
   799   oop* adr_inner_classes() const     { return (oop*)&this->_inner_classes;}
   800   oop* adr_implementors() const      { return (oop*)&this->_implementors[0];}
   801   oop* adr_generic_signature() const { return (oop*)&this->_generic_signature;}
   802   oop* adr_bootstrap_method() const  { return (oop*)&this->_bootstrap_method;}
   803   oop* adr_methods_jmethod_ids() const             { return (oop*)&this->_methods_jmethod_ids;}
   804   oop* adr_methods_cached_itable_indices() const   { return (oop*)&this->_methods_cached_itable_indices;}
   805   oop* adr_class_annotations() const   { return (oop*)&this->_class_annotations;}
   806   oop* adr_fields_annotations() const  { return (oop*)&this->_fields_annotations;}
   807   oop* adr_methods_annotations() const { return (oop*)&this->_methods_annotations;}
   808   oop* adr_methods_parameter_annotations() const { return (oop*)&this->_methods_parameter_annotations;}
   809   oop* adr_methods_default_annotations() const { return (oop*)&this->_methods_default_annotations;}
   811   // Static methods that are used to implement member methods where an exposed this pointer
   812   // is needed due to possible GCs
   813   static bool link_class_impl                           (instanceKlassHandle this_oop, bool throw_verifyerror, TRAPS);
   814   static bool verify_code                               (instanceKlassHandle this_oop, bool throw_verifyerror, TRAPS);
   815   static void initialize_impl                           (instanceKlassHandle this_oop, TRAPS);
   816   static void eager_initialize_impl                     (instanceKlassHandle this_oop);
   817   static void set_initialization_state_and_notify_impl  (instanceKlassHandle this_oop, ClassState state, TRAPS);
   818   static void call_class_initializer_impl               (instanceKlassHandle this_oop, TRAPS);
   819   static klassOop array_klass_impl                      (instanceKlassHandle this_oop, bool or_null, int n, TRAPS);
   820   static void do_local_static_fields_impl               (instanceKlassHandle this_oop, void f(fieldDescriptor* fd, TRAPS), TRAPS);
   821   /* jni_id_for_impl for jfieldID only */
   822   static JNIid* jni_id_for_impl                         (instanceKlassHandle this_oop, int offset);
   824   // Returns the array class for the n'th dimension
   825   klassOop array_klass_impl(bool or_null, int n, TRAPS);
   827   // Returns the array class with this class as element type
   828   klassOop array_klass_impl(bool or_null, TRAPS);
   830 public:
   831   // sharing support
   832   virtual void remove_unshareable_info();
   833   void field_names_and_sigs_iterate(OopClosure* closure);
   835   // jvm support
   836   jint compute_modifier_flags(TRAPS) const;
   838 public:
   839   // JVMTI support
   840   jint jvmti_class_status() const;
   842  public:
   843   // Printing
   844   void oop_print_value_on(oop obj, outputStream* st);
   845 #ifndef PRODUCT
   846   void oop_print_on      (oop obj, outputStream* st);
   848   void print_dependent_nmethods(bool verbose = false);
   849   bool is_dependent_nmethod(nmethod* nm);
   850 #endif
   852   // Verification
   853   const char* internal_name() const;
   854   void oop_verify_on(oop obj, outputStream* st);
   856 #ifndef PRODUCT
   857   static void verify_class_klass_nonstatic_oop_maps(klassOop k) PRODUCT_RETURN;
   858 #endif
   859 };
   861 inline methodOop instanceKlass::method_at_vtable(int index)  {
   862 #ifndef PRODUCT
   863   assert(index >= 0, "valid vtable index");
   864   if (DebugVtables) {
   865     verify_vtable_index(index);
   866   }
   867 #endif
   868   vtableEntry* ve = (vtableEntry*)start_of_vtable();
   869   return ve[index].method();
   870 }
   872 inline typeArrayOop instanceKlass::get_method_annotations_from(int idnum, objArrayOop annos) {
   873   if (annos == NULL || annos->length() <= idnum) {
   874     return NULL;
   875   }
   876   return typeArrayOop(annos->obj_at(idnum));
   877 }
   879 // for adding methods
   880 // UNSET_IDNUM return means no more ids available
   881 inline u2 instanceKlass::next_method_idnum() {
   882   if (_idnum_allocated_count == constMethodOopDesc::MAX_IDNUM) {
   883     return constMethodOopDesc::UNSET_IDNUM; // no more ids available
   884   } else {
   885     return _idnum_allocated_count++;
   886   }
   887 }
   890 /* JNIid class for jfieldIDs only */
   891 class JNIid: public CHeapObj {
   892   friend class VMStructs;
   893  private:
   894   klassOop           _holder;
   895   JNIid*             _next;
   896   int                _offset;
   897 #ifdef ASSERT
   898   bool               _is_static_field_id;
   899 #endif
   901  public:
   902   // Accessors
   903   klassOop holder() const         { return _holder; }
   904   int offset() const              { return _offset; }
   905   JNIid* next()                   { return _next; }
   906   // Constructor
   907   JNIid(klassOop holder, int offset, JNIid* next);
   908   // Identifier lookup
   909   JNIid* find(int offset);
   911   // Garbage collection support
   912   oop* holder_addr() { return (oop*)&_holder; }
   913   void oops_do(OopClosure* f);
   914   static void deallocate(JNIid* id);
   915   // Debugging
   916 #ifdef ASSERT
   917   bool is_static_field_id() const { return _is_static_field_id; }
   918   void set_is_static_field_id()   { _is_static_field_id = true; }
   919 #endif
   920   void verify(klassOop holder);
   921 };
   924 // If breakpoints are more numerous than just JVMTI breakpoints,
   925 // consider compressing this data structure.
   926 // It is currently a simple linked list defined in methodOop.hpp.
   928 class BreakpointInfo;
   931 // A collection point for interesting information about the previous
   932 // version(s) of an instanceKlass. This class uses weak references to
   933 // the information so that the information may be collected as needed
   934 // by the system. If the information is shared, then a regular
   935 // reference must be used because a weak reference would be seen as
   936 // collectible. A GrowableArray of PreviousVersionNodes is attached
   937 // to the instanceKlass as needed. See PreviousVersionWalker below.
   938 class PreviousVersionNode : public CHeapObj {
   939  private:
   940   // A shared ConstantPool is never collected so we'll always have
   941   // a reference to it so we can update items in the cache. We'll
   942   // have a weak reference to a non-shared ConstantPool until all
   943   // of the methods (EMCP or obsolete) have been collected; the
   944   // non-shared ConstantPool becomes collectible at that point.
   945   jobject _prev_constant_pool;  // regular or weak reference
   946   bool    _prev_cp_is_weak;     // true if not a shared ConstantPool
   948   // If the previous version of the instanceKlass doesn't have any
   949   // EMCP methods, then _prev_EMCP_methods will be NULL. If all the
   950   // EMCP methods have been collected, then _prev_EMCP_methods can
   951   // have a length of zero.
   952   GrowableArray<jweak>* _prev_EMCP_methods;
   954 public:
   955   PreviousVersionNode(jobject prev_constant_pool, bool prev_cp_is_weak,
   956     GrowableArray<jweak>* prev_EMCP_methods);
   957   ~PreviousVersionNode();
   958   jobject prev_constant_pool() const {
   959     return _prev_constant_pool;
   960   }
   961   GrowableArray<jweak>* prev_EMCP_methods() const {
   962     return _prev_EMCP_methods;
   963   }
   964 };
   967 // A Handle-ized version of PreviousVersionNode.
   968 class PreviousVersionInfo : public ResourceObj {
   969  private:
   970   constantPoolHandle   _prev_constant_pool_handle;
   971   // If the previous version of the instanceKlass doesn't have any
   972   // EMCP methods, then _prev_EMCP_methods will be NULL. Since the
   973   // methods cannot be collected while we hold a handle,
   974   // _prev_EMCP_methods should never have a length of zero.
   975   GrowableArray<methodHandle>* _prev_EMCP_method_handles;
   977 public:
   978   PreviousVersionInfo(PreviousVersionNode *pv_node);
   979   ~PreviousVersionInfo();
   980   constantPoolHandle prev_constant_pool_handle() const {
   981     return _prev_constant_pool_handle;
   982   }
   983   GrowableArray<methodHandle>* prev_EMCP_method_handles() const {
   984     return _prev_EMCP_method_handles;
   985   }
   986 };
   989 // Helper object for walking previous versions. This helper cleans up
   990 // the Handles that it allocates when the helper object is destroyed.
   991 // The PreviousVersionInfo object returned by next_previous_version()
   992 // is only valid until a subsequent call to next_previous_version() or
   993 // the helper object is destroyed.
   994 class PreviousVersionWalker : public StackObj {
   995  private:
   996   GrowableArray<PreviousVersionNode *>* _previous_versions;
   997   int                                   _current_index;
   998   // Fields for cleaning up when we are done walking the previous versions:
   999   // A HandleMark for the PreviousVersionInfo handles:
  1000   HandleMark                            _hm;
  1002   // It would be nice to have a ResourceMark field in this helper also,
  1003   // but the ResourceMark code says to be careful to delete handles held
  1004   // in GrowableArrays _before_ deleting the GrowableArray. Since we
  1005   // can't guarantee the order in which the fields are destroyed, we
  1006   // have to let the creator of the PreviousVersionWalker object do
  1007   // the right thing. Also, adding a ResourceMark here causes an
  1008   // include loop.
  1010   // A pointer to the current info object so we can handle the deletes.
  1011   PreviousVersionInfo *                 _current_p;
  1013  public:
  1014   PreviousVersionWalker(instanceKlass *ik);
  1015   ~PreviousVersionWalker();
  1017   // Return the interesting information for the next previous version
  1018   // of the klass. Returns NULL if there are no more previous versions.
  1019   PreviousVersionInfo* next_previous_version();
  1020 };

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