[heap] Prevent direct access to ExternalStringTable.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 404 matching lines @@
   V(BooleanMap)                         \
   V(UninitializedMap)                   \
   V(ArgumentsMarkerMap)                 \
   V(JSMessageObjectMap)                 \
   V(ForeignMap)                         \
   V(NeanderMap)                         \
   V(empty_string)                       \
   PRIVATE_SYMBOL_LIST(V)
 
 // Forward declarations.
+class HeapObjectsFilter;
 class HeapStats;
 class Isolate;
 class MemoryReducer;
 class WeakObjectRetainer;
 
 
-typedef String* (*ExternalStringTableUpdaterCallback)(Heap* heap,
-                                                      Object** pointer);
-
-
 // A queue of objects promoted during scavenge. Each object is accompanied
 // by it's size to avoid dereferencing a map pointer for scanning.
 // The last page in to-space is used for the promotion queue. On conflict
 // during scavenge, the promotion queue is allocated externally and all
 // entries are copied to the external queue.
 class PromotionQueue {
  public:
   explicit PromotionQueue(Heap* heap)
       : front_(NULL),
         rear_(NULL),
@@ skipping 89 matching lines @@
   void RelocateQueueHead();
 
   DISALLOW_COPY_AND_ASSIGN(PromotionQueue);
 };
 
 
 typedef void (*ScavengingCallback)(Map* map, HeapObject** slot,
                                    HeapObject* object);
 
 
-// External strings table is a place where all external strings are
-// registered.  We need to keep track of such strings to properly
-// finalize them.
-class ExternalStringTable {
- public:
-  // Registers an external string.
-  inline void AddString(String* string);
-
-  inline void Iterate(ObjectVisitor* v);
-
-  // Restores internal invariant and gets rid of collected strings.
-  // Must be called after each Iterate() that modified the strings.
-  void CleanUp();
-
-  // Destroys all allocated memory.
-  void TearDown();
-
- private:
-  explicit ExternalStringTable(Heap* heap) : heap_(heap) {}
-
-  friend class Heap;
-
-  inline void Verify();
-
-  inline void AddOldString(String* string);
-
-  // Notifies the table that only a prefix of the new list is valid.
-  inline void ShrinkNewStrings(int position);
-
-  // To speed up scavenge collections new space string are kept
-  // separate from old space strings.
-  List<Object*> new_space_strings_;
-  List<Object*> old_space_strings_;
-
-  Heap* heap_;
-
-  DISALLOW_COPY_AND_ASSIGN(ExternalStringTable);
-};
-
-
 enum ArrayStorageAllocationMode {
   DONT_INITIALIZE_ARRAY_ELEMENTS,
   INITIALIZE_ARRAY_ELEMENTS_WITH_HOLE
 };
 
 
 class Heap {
  public:
   // Declare all the root indices.  This defines the root list order.
   enum RootListIndex {
@@ skipping 269 matching lines @@
   // Iterates the whole code space to clear all ICs of the given kind.
   void ClearAllICsByKind(Code::Kind kind);
 
   // FreeSpace objects have a null map after deserialization. Update the map.
   void RepairFreeListsAfterDeserialization();
 
   // Move len elements within a given array from src_index index to dst_index
   // index.
   void MoveElements(FixedArray* array, int dst_index, int src_index, int len);
 
-  // Finalizes an external string by deleting the associated external
-  // data and clearing the resource pointer.
-  inline void FinalizeExternalString(String* string);
-
   // Initialize a filler object to keep the ability to iterate over the heap
   // when introducing gaps within pages.
   void CreateFillerObjectAt(Address addr, int size);
 
   bool CanMoveObjectStart(HeapObject* object);
 
   // Maintain consistency of live bytes during incremental marking.
   void AdjustLiveBytes(HeapObject* object, int by, InvocationMode mode);
 
   // Trim the given array from the left. Note that this relocates the object
@@ skipping 326 matching lines @@
   GCTracer* tracer() { return tracer_; }
 
   PromotionQueue* promotion_queue() { return &promotion_queue_; }
 
   inline Isolate* isolate();
 
   MarkCompactCollector* mark_compact_collector() {
     return &mark_compact_collector_;
   }
 
-  ExternalStringTable* external_string_table() {
-    return &external_string_table_;
-  }
-
   // ===========================================================================
   // Root set access. ==========================================================
   // ===========================================================================
 
   // Heap root getters.  We have versions with and without type::cast() here.
   // You can't use type::cast during GC because the assert fails.
   // TODO(1490): Try removing the unchecked accessors, now that GC marking does
   // not corrupt the map.
 #define ROOT_ACCESSOR(type, name, camel_name)                         \
   inline type* name();                                                \
@@ skipping 149 matching lines @@
   // an estimate increment. Returns the remaining time that cannot be used
   // for incremental marking anymore because a single step would exceed the
   // deadline.
   double AdvanceIncrementalMarking(
       intptr_t step_size_in_bytes, double deadline_in_ms,
       IncrementalMarking::StepActions step_actions);
 
   IncrementalMarking* incremental_marking() { return &incremental_marking_; }
 
   // ===========================================================================
+  // External string table API. ================================================
+  // ===========================================================================
+
+  // Registers an external string.
+  inline void AddExternalString(String* string);

[Michael Starzinger, 2015/08/25 14:18:30]

Wasn't sure whether "AddExternalString" or "RegisterExternalString" would be a
better name for this. WDYT? Happy to change it.

[Michael Lippautz, 2015/08/25 17:23:37]

We already have a couple of Register*() methods. Let's rename it.

[Michael Starzinger, 2015/08/26 08:39:57]

Done.

+
+  // Finalizes an external string by deleting the associated external
+  // data and clearing the resource pointer.
+  inline void FinalizeExternalString(String* string);
+
+  // ===========================================================================
   // Methods checking/returning the space of a given object/address. ===========
   // ===========================================================================
 
   // Returns whether the object resides in new space.
   inline bool InNewSpace(Object* object);
   inline bool InNewSpace(Address address);
   inline bool InNewSpacePage(Address address);
   inline bool InFromSpace(Object* object);
   inline bool InToSpace(Object* object);
 
@@ skipping 200 matching lines @@
   void PrintHandles();
 
   // Report heap statistics.
   void ReportHeapStatistics(const char* title);
   void ReportCodeStatistics(const char* title);
 #endif
 
  private:
   class UnmapFreeMemoryTask;
 
+  // External strings table is a place where all external strings are
+  // registered.  We need to keep track of such strings to properly
+  // finalize them.
+  class ExternalStringTable {
+   public:
+    // Registers an external string.
+    inline void AddString(String* string);
+
+    inline void Iterate(ObjectVisitor* v);
+
+    // Restores internal invariant and gets rid of collected strings.
+    // Must be called after each Iterate() that modified the strings.
+    void CleanUp();
+
+    // Destroys all allocated memory.
+    void TearDown();
+
+   private:
+    explicit ExternalStringTable(Heap* heap) : heap_(heap) {}
+
+    friend class Heap;

[Michael Lippautz, 2015/08/25 17:23:37]

Move to bottom.

[Michael Starzinger, 2015/08/26 08:39:57]

Done.

+
+    inline void Verify();
+
+    inline void AddOldString(String* string);
+
+    // Notifies the table that only a prefix of the new list is valid.
+    inline void ShrinkNewStrings(int position);
+
+    // To speed up scavenge collections new space string are kept
+    // separate from old space strings.
+    List<Object*> new_space_strings_;
+    List<Object*> old_space_strings_;
+
+    Heap* heap_;
+
+    DISALLOW_COPY_AND_ASSIGN(ExternalStringTable);
+  };
+
   struct StrongRootsList;
 
   struct StringTypeTable {
     InstanceType type;
     int size;
     RootListIndex index;
   };
 
   struct ConstantStringTable {
     const char* contents;
@@ skipping 13 matching lines @@
 
     bool operator==(const GCCallbackPair& other) const {
       return other.callback == callback;
     }
 
     v8::Isolate::GCCallback callback;
     GCType gc_type;
     bool pass_isolate;
   };
 
+  typedef String* (*ExternalStringTableUpdaterCallback)(Heap* heap,
+                                                        Object** pointer);
+
   static const int kInitialStringTableSize = 2048;
   static const int kInitialEvalCacheSize = 64;
   static const int kInitialNumberStringCacheSize = 256;
 
   static const int kRememberedUnmappedPages = 128;
 
   static const StringTypeTable string_type_table[];
   static const ConstantStringTable constant_string_table[];
   static const StructTable struct_table[];
 
@@ skipping 903 matching lines @@
 // these can only iterate over one space only.
 //
 // HeapIterator ensures there is no allocation during its lifetime
 // (using an embedded DisallowHeapAllocation instance).
 //
 // HeapIterator can skip free list nodes (that is, de-allocated heap
 // objects that still remain in the heap). As implementation of free
 // nodes filtering uses GC marks, it can't be used during MS/MC GC
 // phases. Also, it is forbidden to interrupt iteration in this mode,
 // as this will leave heap objects marked (and thus, unusable).
-class HeapObjectsFilter;
-
 class HeapIterator BASE_EMBEDDED {
  public:
   enum HeapObjectsFiltering { kNoFiltering, kFilterUnreachable };
 
   explicit HeapIterator(Heap* heap);
   HeapIterator(Heap* heap, HeapObjectsFiltering filtering);
   ~HeapIterator();
 
   HeapObject* next();
   void reset();
@@ skipping 199 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_