[vm, gc] Require a safepoint for heap iteration.

runtime/vm/heap.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_HEAP_H_
 #define RUNTIME_VM_HEAP_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/flags.h"
@@ skipping 75 matching lines @@
   // Move external size from new to old space. Does not by itself trigger GC.
   void PromoteExternal(intptr_t size);
 
   // Heap contains the specified address.
   bool Contains(uword addr) const;
   bool NewContains(uword addr) const;
   bool OldContains(uword addr) const;
   bool CodeContains(uword addr) const;
   bool DataContains(uword addr) const;
 
-  void IterateObjects(ObjectVisitor* visitor) const;
-  void IterateOldObjects(ObjectVisitor* visitor) const;
-  void IterateOldObjectsNoImagePages(ObjectVisitor* visitor) const;
-  void IterateObjectPointers(ObjectVisitor* visitor) const;
-
   // Find an object by visiting all pointers in the specified heap space,
   // the 'visitor' is used to determine if an object is found or not.
   // The 'visitor' function should be set up to return true if the
   // object is found, traversal through the heap space stops at that
   // point.
   // The 'visitor' function should return false if the object is not found,
   // traversal through the heap space continues.
   // Returns null object if nothing is found.
   RawInstructions* FindObjectInCodeSpace(FindObjectVisitor* visitor) const;
   RawObject* FindOldObject(FindObjectVisitor* visitor) const;
@@ skipping 242 matching lines @@
   // This heap is in read-only mode: No allocation is allowed.
   bool read_only_;
 
   // GC on the heap is in progress.
   Monitor gc_in_progress_monitor_;
   bool gc_new_space_in_progress_;
   bool gc_old_space_in_progress_;
 
   friend class Become;       // VisitObjectPointers
   friend class Precompiler;  // VisitObjects
-  friend class ObjectGraph;  // VisitObjects
   friend class Unmarker;     // VisitObjects
   friend class ServiceEvent;
   friend class PageSpace;             // VerifyGC
   friend class IsolateReloadContext;  // VisitObjects
   friend class ClassFinalizer;        // VisitObjects
+  friend class HeapIterationScope;    // VisitObjects
 
   DISALLOW_COPY_AND_ASSIGN(Heap);
 };
 
 class HeapIterationScope : public StackResource {
  public:
   explicit HeapIterationScope(bool writable = false);
   ~HeapIterationScope();
 
+  void IterateObjects(ObjectVisitor* visitor) const;
+  void IterateObjectsNoImagePages(ObjectVisitor* visitor) const;
+  void IterateOldObjects(ObjectVisitor* visitor) const;
+  void IterateOldObjectsNoImagePages(ObjectVisitor* visitor) const;
+
+  void IterateVMIsolateObjects(ObjectVisitor* visitor) const;
+
+  void IterateObjectPointers(ObjectPointerVisitor* visitor,
+                             bool validate_frames);
+  void IterateStackPointers(ObjectPointerVisitor* visitor,
+                            bool validate_frames);
+
  private:
-  NoSafepointScope no_safepoint_scope_;
+  Heap* heap_;
   PageSpace* old_space_;
   bool writable_;
 
   DISALLOW_COPY_AND_ASSIGN(HeapIterationScope);
 };
 
 class NoHeapGrowthControlScope : public StackResource {
  public:
   NoHeapGrowthControlScope();
   ~NoHeapGrowthControlScope();
 
  private:
   bool current_growth_controller_state_;
   DISALLOW_COPY_AND_ASSIGN(NoHeapGrowthControlScope);
 };
 
 // Note: During this scope, the code pages are non-executable.
 class WritableVMIsolateScope : StackResource {
  public:
   explicit WritableVMIsolateScope(Thread* thread);
   ~WritableVMIsolateScope();
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_HEAP_H_