heap: allow allocation in gc prologue/epilogue

src/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2492 matching lines @@
 
   VisitorDispatchTable<ScavengingCallback> scavenging_visitors_table_;
 
   MemoryChunk* chunks_queued_for_free_;
 
   Mutex* relocation_mutex_;
 #ifdef DEBUG
   bool relocation_mutex_locked_by_optimizer_thread_;
 #endif  // DEBUG;
 
+  int gc_callbacks_depth_;
+
   friend class Factory;
   friend class GCTracer;
   friend class DisallowAllocationFailure;
   friend class AlwaysAllocateScope;
   friend class Page;
   friend class Isolate;
   friend class MarkCompactCollector;
   friend class MarkCompactMarkingVisitor;
   friend class MapCompact;
 #ifdef VERIFY_HEAP
   friend class NoWeakObjectVerificationScope;
 #endif
+  friend class GCCallbacksScope;
 
   DISALLOW_COPY_AND_ASSIGN(Heap);
 };
 
 
 class HeapStats {
  public:
   static const int kStartMarker = 0xDECADE00;
   static const int kEndMarker = 0xDECADE01;
 
@@ skipping 52 matching lines @@
 
 #ifdef VERIFY_HEAP
 class NoWeakObjectVerificationScope {
  public:
   inline NoWeakObjectVerificationScope();
   inline ~NoWeakObjectVerificationScope();
 };
 #endif
 
 
+class GCCallbacksScope {
+ public:
+  explicit inline GCCallbacksScope(Heap* heap);
+  inline ~GCCallbacksScope();
+
+  inline bool CheckReenter();
+
+ private:
+  Heap* heap_;
+};
+
+
 // Visitor class to verify interior pointers in spaces that do not contain
 // or care about intergenerational references. All heap object pointers have to
 // point into the heap to a location that has a map pointer at its first word.
 // Caveat: Heap::Contains is an approximation because it can return true for
 // objects in a heap space but above the allocation pointer.
 class VerifyPointersVisitor: public ObjectVisitor {
  public:
   inline void VisitPointers(Object** start, Object** end);
 };
 
@@ skipping 507 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_