Ensure strings are never externalized as a side-effect of doing a GC.

Review URL: http://codereview.chromium.org/7105016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8142 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/api.cc

@@ -4264,6 +4264,9 @@ bool v8::String::MakeExternal(v8::String::ExternalStringResource* resource) {
   if (isolate->string_tracker()->IsFreshUnusedString(obj)) {
     return false;
   }
+  if (isolate->heap()->IsInGCPostProcessing()) {
+    return false;
+  }
   bool result = obj->MakeExternal(resource);
   if (result && !obj->IsSymbol()) {
     isolate->heap()->external_string_table()->AddString(*obj);
@@ -4296,6 +4299,9 @@ bool v8::String::MakeExternal(
   if (isolate->string_tracker()->IsFreshUnusedString(obj)) {
     return false;
   }
+  if (isolate->heap()->IsInGCPostProcessing()) {
+    return false;
+  }
   bool result = obj->MakeExternal(resource);
   if (result && !obj->IsSymbol()) {
     isolate->heap()->external_string_table()->AddString(*obj);

src/heap.cc

@@ -107,6 +107,7 @@ Heap::Heap()
       cell_space_(NULL),
       lo_space_(NULL),
       gc_state_(NOT_IN_GC),
+      gc_post_processing_depth_(0),
       mc_count_(0),
       ms_count_(0),
       gc_count_(0),
@@ -794,11 +795,13 @@ bool Heap::PerformGarbageCollection(GarbageCollector collector,
 
   isolate_->counters()->objs_since_last_young()->Set(0);
   
+  gc_post_processing_depth_++;
   { DisableAssertNoAllocation allow_allocation;
     GCTracer::Scope scope(tracer, GCTracer::Scope::EXTERNAL);
     next_gc_likely_to_collect_more =
         isolate_->global_handles()->PostGarbageCollectionProcessing(collector);
   }
+  gc_post_processing_depth_--;
 
   // Update relocatables.
   Relocatable::PostGarbageCollectionProcessing();

src/heap.h

@@ -1054,6 +1054,8 @@ class Heap {
   enum HeapState { NOT_IN_GC, SCAVENGE, MARK_COMPACT };
   inline HeapState gc_state() { return gc_state_; }
   
+  inline bool IsInGCPostProcessing() { return gc_post_processing_depth_ > 0; }
+
 #ifdef DEBUG
   bool IsAllocationAllowed() { return allocation_allowed_; }
   inline bool allow_allocation(bool enable);
@@ -1277,6 +1279,7 @@ class Heap {
   CellSpace* cell_space_;
   LargeObjectSpace* lo_space_;
   HeapState gc_state_;
+  int gc_post_processing_depth_;
 
   // Returns the size of object residing in non new spaces.
   intptr_t PromotedSpaceSize();