Heap snapshot: Update user roots definition.

src/heap-snapshot-generator.cc

 // Copyright 2013 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 943 matching lines @@
 };
 
 
 void V8HeapExplorer::ExtractReferences(HeapObject* obj) {
   HeapEntry* heap_entry = GetEntry(obj);
   if (heap_entry == NULL) return;  // No interest in this object.
   int entry = heap_entry->index();
 
   bool extract_indexed_refs = true;
   if (obj->IsJSGlobalProxy()) {
-    ExtractJSGlobalProxyReferences(JSGlobalProxy::cast(obj));
+    ExtractJSGlobalProxyReferences(entry, JSGlobalProxy::cast(obj));
   } else if (obj->IsJSObject()) {
     ExtractJSObjectReferences(entry, JSObject::cast(obj));
   } else if (obj->IsString()) {
     ExtractStringReferences(entry, String::cast(obj));
   } else if (obj->IsContext()) {
     ExtractContextReferences(entry, Context::cast(obj));
   } else if (obj->IsMap()) {
     ExtractMapReferences(entry, Map::cast(obj));
   } else if (obj->IsSharedFunctionInfo()) {
     ExtractSharedFunctionInfoReferences(entry, SharedFunctionInfo::cast(obj));
@@ skipping 12 matching lines @@
     extract_indexed_refs = false;
   }
   if (extract_indexed_refs) {
     SetInternalReference(obj, entry, "map", obj->map(), HeapObject::kMapOffset);
     IndexedReferencesExtractor refs_extractor(this, obj, entry);
     obj->Iterate(&refs_extractor);
   }
 }
 
 
-void V8HeapExplorer::ExtractJSGlobalProxyReferences(JSGlobalProxy* proxy) {
-  // We need to reference JS global objects from snapshot's root.
-  // We use JSGlobalProxy because this is what embedder (e.g. browser)
-  // uses for the global object.
-  Object* object = proxy->map()->prototype();
-  bool is_debug_object = false;
-#ifdef ENABLE_DEBUGGER_SUPPORT
-  is_debug_object = object->IsGlobalObject() &&
-      Isolate::Current()->debug()->IsDebugGlobal(GlobalObject::cast(object));
-#endif
-  if (!is_debug_object) {
-    SetUserGlobalReference(object);
-  }
+void V8HeapExplorer::ExtractJSGlobalProxyReferences(
+    int entry, JSGlobalProxy* proxy) {
+  SetInternalReference(proxy, entry,
+                       "native_context", proxy->native_context(),

[yurys, 2013/06/27 16:26:00]

Can we have a test for this?

As far as I understand global object in Blink consists of 3 objects [1] which
look as a single entity from the application's point of view. One of them is
created to keep global object identity on navigation while the shadow one
actually keeps all user properties. Which one of them is pointed at by the
native_context link?


[1]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

[alph, 2013/06/28 11:58:04]

Don't think checking that we've reported this the only propery of JSGlobalProxy
deserves a test.

+                       JSGlobalProxy::kNativeContextOffset);
 }
 
 
 void V8HeapExplorer::ExtractJSObjectReferences(
     int entry, JSObject* js_obj) {
   HeapObject* obj = js_obj;
   ExtractClosureReferences(js_obj, entry);
   ExtractPropertyReferences(js_obj, entry);
   ExtractElementReferences(js_obj, entry);
   ExtractInternalReferences(js_obj, entry);
@@ skipping 733 matching lines @@
           HeapGraphEdge::kInternal,
           snapshot_->gc_subroot(tag)->index(),
           name,
           child_entry);
     } else {
       filler_->SetIndexedAutoIndexReference(
           is_weak ? HeapGraphEdge::kWeak : HeapGraphEdge::kElement,
           snapshot_->gc_subroot(tag)->index(),
           child_entry);
     }
+
+    // Add a shortcut to JS global object reference at snapshot root.
+    if (child_obj->IsNativeContext()) {
+      Context* context = Context::cast(child_obj);
+      JSObject* proxy = context->global_proxy();
+      if (proxy->IsJSGlobalProxy()) {
+        // We use JSGlobalProxy because that's what embedder (e.g. browser)
+        // uses for the global object.
+        // TODO(alph): consider extracting it as just proxy->global_object()
+        Object* object = proxy->map()->prototype();
+        if (object->IsJSGlobalObject()) {
+          JSGlobalObject* global = JSGlobalObject::cast(object);
+          CHECK(global == context->global_object());

[yurys, 2013/06/28 09:42:18]

Ok, I looked more closely at how we setup global object in bootstraper.cc, in
particular the inner global object [1] and I think we should use
context->global_object() instead.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/bootstrappe...

[alph, 2013/06/28 11:58:04]

Done.

+          bool is_debug_object = false;
+#ifdef ENABLE_DEBUGGER_SUPPORT
+          is_debug_object = Isolate::Current()->debug()->IsDebugGlobal(global);

[yurys, 2013/06/27 16:26:00]

Please use heap_->isolate() instead of Isolate::Current()

[alph, 2013/06/28 11:58:04]

Done.

+#endif
+          if (!is_debug_object && !user_roots_.Contains(global)) {
+            user_roots_.Insert(global);
+            SetUserGlobalReference(global);
+          }
+        }
+      }
+    }
   }
 }
 
 
 const char* V8HeapExplorer::GetStrongGcSubrootName(Object* object) {
   if (strong_gc_subroot_names_.is_empty()) {
 #define NAME_ENTRY(name) strong_gc_subroot_names_.SetTag(heap_->name(), #name);
 #define ROOT_NAME(type, name, camel_name) NAME_ENTRY(name)
     STRONG_ROOT_LIST(ROOT_NAME)
 #undef ROOT_NAME
@@ skipping 895 matching lines @@
 
 
 void HeapSnapshotJSONSerializer::SortHashMap(
     HashMap* map, List<HashMap::Entry*>* sorted_entries) {
   for (HashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p))
     sorted_entries->Add(p);
   sorted_entries->Sort(SortUsingEntryValue);
 }
 
 } }  // namespace v8::internal