Show references from weak containers as weak in heap snapshots.

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 1083 matching lines @@
     }
     return false;
   }
   V8HeapExplorer* generator_;
   HeapObject* parent_obj_;
   int parent_;
   int next_index_;
 };
 
 
-void V8HeapExplorer::ExtractReferences(HeapObject* obj) {
+void V8HeapExplorer::ExtractReferencesPass1(HeapObject* obj) {
+  if (obj->IsFixedArray()) return;  // FixedArrays are processed on pass 2.
+
   HeapEntry* heap_entry = GetEntry(obj);
   if (heap_entry == NULL) return;  // No interest in this object.
   int entry = heap_entry->index();
 
   if (obj->IsJSGlobalProxy()) {
     ExtractJSGlobalProxyReferences(entry, JSGlobalProxy::cast(obj));
   } else if (obj->IsJSArrayBuffer()) {
     ExtractJSArrayBufferReferences(entry, JSArrayBuffer::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));
   } else if (obj->IsScript()) {
     ExtractScriptReferences(entry, Script::cast(obj));
   } else if (obj->IsAccessorPair()) {
     ExtractAccessorPairReferences(entry, AccessorPair::cast(obj));
   } else if (obj->IsCodeCache()) {
     ExtractCodeCacheReferences(entry, CodeCache::cast(obj));
@@ skipping 10 matching lines @@
   }
   SetInternalReference(obj, entry, "map", obj->map(), HeapObject::kMapOffset);
 
   // Extract unvisited fields as hidden references and restore tags
   // of visited fields.
   IndexedReferencesExtractor refs_extractor(this, obj, entry);
   obj->Iterate(&refs_extractor);
 }
 
 
+void V8HeapExplorer::ExtractReferencesPass2(HeapObject* obj) {
+  if (!obj->IsFixedArray()) return;
+
+  HeapEntry* heap_entry = GetEntry(obj);

[yurys, 2014/04/01 15:51:55]

Consider extracting common prologue and epilogue of ExtractReferencesPass{1,2} 
into IterateAndExtractSinglePass.

[alph, 2014/04/01 16:30:03]

Done.

+  if (heap_entry == NULL) return;  // No interest in this object.
+  int entry = heap_entry->index();
+
+  if (obj->IsContext()) {
+    ExtractContextReferences(entry, Context::cast(obj));
+  } else {
+    ExtractFixedArrayReferences(entry, FixedArray::cast(obj));
+  }
+
+  SetInternalReference(obj, entry, "map", obj->map(), HeapObject::kMapOffset);
+
+  // Extract unvisited fields as hidden references and restore tags
+  // of visited fields.
+  IndexedReferencesExtractor refs_extractor(this, obj, entry);
+  obj->Iterate(&refs_extractor);
+}
+
+
 void V8HeapExplorer::ExtractJSGlobalProxyReferences(
     int entry, JSGlobalProxy* proxy) {
   SetInternalReference(proxy, entry,
                        "native_context", proxy->native_context(),
                        JSGlobalProxy::kNativeContextOffset);
 }
 
 
 void V8HeapExplorer::ExtractJSObjectReferences(
     int entry, JSObject* js_obj) {
@@ skipping 154 matching lines @@
 
 void V8HeapExplorer::ExtractMapReferences(int entry, Map* map) {
   if (map->HasTransitionArray()) {
     TransitionArray* transitions = map->transitions();
     int transitions_entry = GetEntry(transitions)->index();
     Object* back_pointer = transitions->back_pointer_storage();
     TagObject(back_pointer, "(back pointer)");
     SetInternalReference(transitions, transitions_entry,
                          "back_pointer", back_pointer);
     TagObject(transitions, "(transition array)");
+    MarkAsWeakContainer(transitions);
     SetInternalReference(map, entry,
                          "transitions", transitions,
                          Map::kTransitionsOrBackPointerOffset);
   } else {
     Object* back_pointer = map->GetBackPointer();
     TagObject(back_pointer, "(back pointer)");
     SetInternalReference(map, entry,
                          "back_pointer", back_pointer,
                          Map::kTransitionsOrBackPointerOffset);
   }
   DescriptorArray* descriptors = map->instance_descriptors();
   TagObject(descriptors, "(map descriptors)");
   SetInternalReference(map, entry,
                        "descriptors", descriptors,
                        Map::kDescriptorsOffset);
 
+  MarkAsWeakContainer(map->code_cache());
   SetInternalReference(map, entry,
                        "code_cache", map->code_cache(),
                        Map::kCodeCacheOffset);
   SetInternalReference(map, entry,
                        "prototype", map->prototype(), Map::kPrototypeOffset);
   SetInternalReference(map, entry,
                        "constructor", map->constructor(),
                        Map::kConstructorOffset);
   TagObject(map->dependent_code(), "(dependent code)");
+  MarkAsWeakContainer(map->dependent_code());
   SetInternalReference(map, entry,
                        "dependent_code", map->dependent_code(),
                        Map::kDependentCodeOffset);
 }
 
 
 void V8HeapExplorer::ExtractSharedFunctionInfoReferences(
     int entry, SharedFunctionInfo* shared) {
   HeapObject* obj = shared;
   String* shared_name = shared->DebugName();
@@ skipping 141 matching lines @@
 void V8HeapExplorer::ExtractCellReferences(int entry, Cell* cell) {
   SetInternalReference(cell, entry, "value", cell->value(), Cell::kValueOffset);
 }
 
 
 void V8HeapExplorer::ExtractPropertyCellReferences(int entry,
                                                    PropertyCell* cell) {
   ExtractCellReferences(entry, cell);
   SetInternalReference(cell, entry, "type", cell->type(),
                        PropertyCell::kTypeOffset);
+  MarkAsWeakContainer(cell->dependent_code());
   SetInternalReference(cell, entry, "dependent_code", cell->dependent_code(),
                        PropertyCell::kDependentCodeOffset);
 }
 
 
 void V8HeapExplorer::ExtractAllocationSiteReferences(int entry,
                                                      AllocationSite* site) {
   SetInternalReference(site, entry, "transition_info", site->transition_info(),
                        AllocationSite::kTransitionInfoOffset);
   SetInternalReference(site, entry, "nested_site", site->nested_site(),
                        AllocationSite::kNestedSiteOffset);
+  MarkAsWeakContainer(site->dependent_code());
   SetInternalReference(site, entry, "dependent_code", site->dependent_code(),
                        AllocationSite::kDependentCodeOffset);
   // Do not visit weak_next as it is not visited by the StaticVisitor,
   // and we're not very interested in weak_next field here.
   STATIC_CHECK(AllocationSite::kWeakNextOffset >=
                AllocationSite::BodyDescriptor::kEndOffset);
 }
 
 
 class JSArrayBufferDataEntryAllocator : public HeapEntriesAllocator {
@@ skipping 25 matching lines @@
     return;
   size_t data_size = NumberToSize(heap_->isolate(), buffer->byte_length());
   JSArrayBufferDataEntryAllocator allocator(data_size, this);
   HeapEntry* data_entry =
       filler_->FindOrAddEntry(buffer->backing_store(), &allocator);
   filler_->SetNamedReference(HeapGraphEdge::kInternal,
                              entry, "backing_store", data_entry);
 }
 
 
+void V8HeapExplorer::ExtractFixedArrayReferences(int entry, FixedArray* array) {
+  bool is_weak = weak_containers_.Contains(array);
+  for (int i = 0, l = array->length(); i < l; ++i) {
+    if (is_weak) {
+      SetWeakReference(array, entry,
+                       i, array->get(i), array->OffsetOfElementAt(i));
+    } else {
+      SetInternalReference(array, entry,
+                           i, array->get(i), array->OffsetOfElementAt(i));
+    }
+  }
+}
+
+
 void V8HeapExplorer::ExtractClosureReferences(JSObject* js_obj, int entry) {
   if (!js_obj->IsJSFunction()) return;
 
   JSFunction* func = JSFunction::cast(js_obj);
   if (func->shared()->bound()) {
     FixedArray* bindings = func->function_bindings();
     SetNativeBindReference(js_obj, entry, "bound_this",
                            bindings->get(JSFunction::kBoundThisIndex));
     SetNativeBindReference(js_obj, entry, "bound_function",
                            bindings->get(JSFunction::kBoundFunctionIndex));
@@ skipping 251 matching lines @@
   // Make sure builtin code objects get their builtin tags
   // first. Otherwise a particular JSFunction object could set
   // its custom name to a generic builtin.
   SetRootGcRootsReference();
   RootsReferencesExtractor extractor(heap_);
   heap_->IterateRoots(&extractor, VISIT_ONLY_STRONG);
   extractor.SetCollectingAllReferences();
   heap_->IterateRoots(&extractor, VISIT_ALL);
   extractor.FillReferences(this);
 
+  // We have to do two passes as sometimes FixedArrays are used
+  // to weakly hold their items, and it's impossible to distinguish
+  // between these cases without processing the array owner first.
+  bool interrupted =
+      IterateAndExtractSinglePass<&V8HeapExplorer::ExtractReferencesPass1>() ||
+      IterateAndExtractSinglePass<&V8HeapExplorer::ExtractReferencesPass2>();
+
+  if (interrupted) {
+    filler_ = NULL;
+    return false;
+  }
+
+  filler_ = NULL;
+  return progress_->ProgressReport(true);
+}
+
+
+template<V8HeapExplorer::ExtractReferencesMethod extractor>
+bool V8HeapExplorer::IterateAndExtractSinglePass() {
   // Now iterate the whole heap.
   bool interrupted = false;
   HeapIterator iterator(heap_, HeapIterator::kFilterUnreachable);
   // Heap iteration with filtering must be finished in any case.
   for (HeapObject* obj = iterator.next();
        obj != NULL;
        obj = iterator.next(), progress_->ProgressStep()) {
-    if (!interrupted) {
-      ExtractReferences(obj);
-      if (!progress_->ProgressReport(false)) interrupted = true;
-    }
+    if (interrupted) continue;
+    (this->*extractor)(obj);
+    if (!progress_->ProgressReport(false)) interrupted = true;
   }
-  if (interrupted) {
-    filler_ = NULL;
-    return false;
-  }
-
-  filler_ = NULL;
-  return progress_->ProgressReport(true);
+  return interrupted;
 }
 
 
 bool V8HeapExplorer::IsEssentialObject(Object* object) {
   return object->IsHeapObject()
       && !object->IsOddball()
       && object != heap_->empty_byte_array()
       && object != heap_->empty_fixed_array()
       && object != heap_->empty_descriptor_array()
       && object != heap_->fixed_array_map()
@@ skipping 115 matching lines @@
   if (IsEssentialObject(child_obj)) {
     filler_->SetNamedReference(HeapGraphEdge::kWeak,
                                parent_entry,
                                reference_name,
                                child_entry);
   }
   IndexedReferencesExtractor::MarkVisitedField(parent_obj, field_offset);
 }
 
 
+void V8HeapExplorer::SetWeakReference(HeapObject* parent_obj,
+                                      int parent_entry,
+                                      int index,
+                                      Object* child_obj,
+                                      int field_offset) {
+  ASSERT(parent_entry == GetEntry(parent_obj)->index());
+  HeapEntry* child_entry = GetEntry(child_obj);
+  if (child_entry == NULL) return;
+  if (IsEssentialObject(child_obj)) {
+    filler_->SetNamedReference(HeapGraphEdge::kWeak,
+                               parent_entry,
+                               names_->GetFormatted("%d", index),
+                               child_entry);
+  }
+  IndexedReferencesExtractor::MarkVisitedField(parent_obj, field_offset);
+}
+
+
 void V8HeapExplorer::SetPropertyReference(HeapObject* parent_obj,
                                           int parent_entry,
                                           Name* reference_name,
                                           Object* child_obj,
                                           const char* name_format_string,
                                           int field_offset) {
   ASSERT(parent_entry == GetEntry(parent_obj)->index());
   HeapEntry* child_entry = GetEntry(child_obj);
   if (child_entry != NULL) {
     HeapGraphEdge::Type type =
@@ skipping 107 matching lines @@
 void V8HeapExplorer::TagObject(Object* obj, const char* tag) {
   if (IsEssentialObject(obj)) {
     HeapEntry* entry = GetEntry(obj);
     if (entry->name()[0] == '\0') {
       entry->set_name(tag);
     }
   }
 }
 
 
+void V8HeapExplorer::MarkAsWeakContainer(Object* object) {
+  if (IsEssentialObject(object)) {

[yurys, 2014/04/01 15:51:55]

Can you add an assert that the object passed in is a FixedArray or change the
parameter type to FixedArray?

[alph, 2014/04/01 16:30:03]

Done.

+    weak_containers_.Insert(object);
+  }
+}
+
+
 class GlobalObjectsEnumerator : public ObjectVisitor {
  public:
   virtual void VisitPointers(Object** start, Object** end) {
     for (Object** p = start; p < end; p++) {
       if ((*p)->IsNativeContext()) {
         Context* context = Context::cast(*p);
         JSObject* proxy = context->global_proxy();
         if (proxy->IsJSGlobalProxy()) {
           Object* global = proxy->map()->prototype();
           if (global->IsJSGlobalObject()) {
@@ skipping 370 matching lines @@
 #endif
 
   // The following code uses heap iterators, so we want the heap to be
   // stable. It should follow TagGlobalObjects as that can allocate.
   DisallowHeapAllocation no_alloc;
 
 #ifdef VERIFY_HEAP
   debug_heap->Verify();
 #endif
 
-  SetProgressTotal(1);  // 1 pass.
+  SetProgressTotal(2);  // 2 passes.
 
 #ifdef VERIFY_HEAP
   debug_heap->Verify();
 #endif
 
   if (!FillReferences()) return false;
 
   snapshot_->FillChildren();
   snapshot_->RememberLastJSObjectId();
 
@@ skipping 558 matching lines @@
   writer_->AddString("\"<dummy>\"");
   for (int i = 1; i < sorted_strings.length(); ++i) {
     writer_->AddCharacter(',');
     SerializeString(sorted_strings[i]);
     if (writer_->aborted()) return;
   }
 }
 
 
 } }  // namespace v8::internal