Add a second kind of HandleScope that ties the lifetime of Handles created in its scope to the life…

src/api.h

Index: src/api.h
diff --git a/src/api.h b/src/api.h
index 58e6a6e410380bf96e6eafb94dba5ff1a7ba5f38..7c4b3dbb592554c905d65f0833fb309cb7895d9d 100644
--- a/src/api.h
+++ b/src/api.h
@@ -409,7 +409,10 @@ class HandleScopeImplementer {
         entered_contexts_(0),
         saved_contexts_(0),
         spare_(NULL),
-        call_depth_(0) { }
+        call_depth_(0),
+        last_non_persistent_block_(NULL),
+        last_non_persistent_handle_(NULL),
+        persistent_extensions_head_(NULL) { }
 
   ~HandleScopeImplementer() {
     DeleteArray(spare_);
@@ -425,10 +428,21 @@ class HandleScopeImplementer {
   void Iterate(v8::internal::ObjectVisitor* v);
   static char* Iterate(v8::internal::ObjectVisitor* v, char* data);
 
+  struct PersistentExtensions {

[danno, 2012/06/24 11:07:03]

Perhaps DeferredReleaseHandleScope?

+    List<Object**> blocks;
+    Object** last_block_end;
+    PersistentExtensions* previous;
+    PersistentExtensions* next;
+  };
 
   inline internal::Object** GetSpareOrNewBlock();
   inline void DeleteExtensions(internal::Object** prev_limit);
 
+  // HideExtensions must be called _before_ the next field in
+  // HandleScopeData is reverted.
+  PersistentExtensions* PersistExtensions(internal::Object** prev_limit);

[danno, 2012/06/24 11:07:03]

BeginDeferredHandleScope?

+  void ReleaseExtensions(PersistentExtensions* extension);

[danno, 2012/06/24 11:07:03]

Should be a private method only called by the DeferredReleaseHandleScopes'
destructor.

+
   inline void IncrementCallDepth() {call_depth_++;}
   inline void DecrementCallDepth() {call_depth_--;}
   inline bool CallDepthIsZero() { return call_depth_ == 0; }
@@ -446,6 +460,19 @@ class HandleScopeImplementer {
 
   inline List<internal::Object**>* blocks() { return &blocks_; }
 
+  void begin_persistence() {

[danno, 2012/06/24 11:07:03]

I think you can merge this with PersistExtensions if it becomes
BeginDeferredHandleScope.

+    // We only track one such special block.
+    ASSERT(!last_non_persistent_block_);
+    last_non_persistent_block_ = blocks_.last();
+    last_non_persistent_handle_ = isolate_->handle_scope_data()->next;
+  }
+
+  void end_persistence() {

[danno, 2012/06/24 11:07:03]

This should by a private method called "DeferHandleScope" that is only called by
the "Defer" method on the DeferredHandleScope, which itself should only be
called by the CompilationHandleScopes's DetachHandles method.

+    ASSERT(last_non_persistent_block_);
+    last_non_persistent_block_ = NULL;
+    last_non_persistent_handle_ = NULL;
+  }
+
  private:
   void ResetAfterArchive() {
     blocks_.Initialize(0);
@@ -479,6 +506,9 @@ class HandleScopeImplementer {
   int call_depth_;
   // This is only used for threading support.
   v8::ImplementationUtilities::HandleScopeData handle_scope_data_;
+  Object** last_non_persistent_block_;
+  Object** last_non_persistent_handle_;
+  PersistentExtensions* persistent_extensions_head_;
 
   void IterateThis(ObjectVisitor* v);
   char* RestoreThreadHelper(char* from);