Avoid to list internal Arrays in _GetRetainingPath api

runtime/vm/object_graph.cc

Index: runtime/vm/object_graph.cc
diff --git a/runtime/vm/object_graph.cc b/runtime/vm/object_graph.cc
index bbecac73b11bfdaf1717a3bf6a33c81fb8769b9e..8e235b32bfc1de06f5f57ecc76ee1edf0f9efd03 100644
--- a/runtime/vm/object_graph.cc
+++ b/runtime/vm/object_graph.cc
@@ -319,6 +319,30 @@ class RetainingPathVisitor : public ObjectGraph::Visitor {
     }
   }
 
+  bool ShouldStop(RawObject* obj) {
+    // A static field is considered a root from a language point of view.
+    if (obj->IsField()) {
+      const Field& field = Field::Handle(static_cast<RawField*>(obj));
+      return field.is_static();
+    }
+    return false;
+  }
+
+  void StartList() {
+    wasLastArray_ = false;

[Cutch, 2016/08/12 14:23:39]

C++ style guide says variables are lower_case_like_this:

was_last_array_;

[cbernaschina, 2016/08/12 17:28:24]

Done.

+  }
+
+  bool ShouldOverwrite(RawObject* obj) {

[Cutch, 2016/08/12 14:23:40]

ShouldReplace?

[cbernaschina, 2016/08/12 17:28:24]

Changed approach, and name

+    // A GrowableObjectArray overwrites its internal storage.
+    // Keeping both of them in the list is redundant.
+    if (wasLastArray_ && obj->IsGrowableObjectArray()) {
+      wasLastArray_ = false;
+      return true;
+    }
+    wasLastArray_ = obj->IsArray();
+    return false;
+  }
+
   virtual Direction VisitObject(ObjectGraph::StackIterator* it) {
     if (it->Get() != obj_) {
       if (ShouldSkip(it->Get())) {
@@ -330,7 +354,11 @@ class RetainingPathVisitor : public ObjectGraph::Visitor {
       HANDLESCOPE(thread_);
       Object& current = Object::Handle();
       Smi& offset_from_parent = Smi::Handle();
+      StartList();
       do {
+        if (ShouldOverwrite(it->Get())) {
+          --length_;
+        }
         intptr_t obj_index = length_ * 2;
         intptr_t offset_index = obj_index + 1;
         if (!path_.IsNull() && offset_index < path_.Length()) {
@@ -340,7 +368,7 @@ class RetainingPathVisitor : public ObjectGraph::Visitor {
           path_.SetAt(offset_index, offset_from_parent);
         }
         ++length_;
-      } while (it->MoveToParent());
+      } while (!ShouldStop(it->Get()) && it->MoveToParent());
       return kAbort;
     }
   }
@@ -350,6 +378,7 @@ class RetainingPathVisitor : public ObjectGraph::Visitor {
   RawObject* obj_;
   const Array& path_;
   intptr_t length_;
+  bool wasLastArray_;
 };