Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1323 insertions, 0 deletions

diff --git a/js/src/vm/UbiNodeCensus.cpp b/js/src/vm/UbiNodeCensus.cpp
new file mode 100644
index 0000000000..a313852f59
--- /dev/null
+++ b/js/src/vm/UbiNodeCensus.cpp
@@ -0,0 +1,1323 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "js/UbiNodeCensus.h"
+
+#include "builtin/MapObject.h"
+#include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
+#include "js/Printer.h"
+#include "util/Text.h"
+#include "vm/Compartment.h"
+#include "vm/JSContext.h"
+#include "vm/PlainObject.h"  // js::PlainObject
+
+#include "vm/NativeObject-inl.h"
+
+using namespace js;
+
+namespace JS {
+namespace ubi {
+
+JS_PUBLIC_API void CountDeleter::operator()(CountBase* ptr) {
+  if (!ptr) {
+    return;
+  }
+
+  // Downcast to our true type and destruct, as guided by our CountType
+  // pointer.
+  ptr->destruct();
+  js_free(ptr);
+}
+
+/*** Count Types ************************************************************/
+
+// The simplest type: just count everything.
+class SimpleCount : public CountType {
+  struct Count : CountBase {
+    size_t totalBytes_;
+
+    explicit Count(SimpleCount& count) : CountBase(count), totalBytes_(0) {}
+  };
+
+  UniqueTwoByteChars label;
+  bool reportCount : 1;
+  bool reportBytes : 1;
+
+ public:
+  explicit SimpleCount(UniqueTwoByteChars& label, bool reportCount = true,
+                       bool reportBytes = true)
+      : CountType(),
+        label(std::move(label)),
+        reportCount(reportCount),
+        reportBytes(reportBytes) {}
+
+  explicit SimpleCount()
+      : CountType(), label(nullptr), reportCount(true), reportBytes(true) {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override {
+    return CountBasePtr(js_new<Count>(*this));
+  }
+  void traceCount(CountBase& countBase, JSTracer* trc) override {}
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+bool SimpleCount::count(CountBase& countBase,
+                        mozilla::MallocSizeOf mallocSizeOf, const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+  if (reportBytes) {
+    count.totalBytes_ += node.size(mallocSizeOf);
+  }
+  return true;
+}
+
+bool SimpleCount::report(JSContext* cx, CountBase& countBase,
+                         MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+  Rooted<PlainObject*> obj(cx, NewPlainObject(cx));
+  if (!obj) {
+    return false;
+  }
+
+  RootedValue countValue(cx, NumberValue(count.total_));
+  if (reportCount &&
+      !DefineDataProperty(cx, obj, cx->names().count, countValue)) {
+    return false;
+  }
+
+  RootedValue bytesValue(cx, NumberValue(count.totalBytes_));
+  if (reportBytes &&
+      !DefineDataProperty(cx, obj, cx->names().bytes, bytesValue)) {
+    return false;
+  }
+
+  if (label) {
+    JSString* labelString = JS_NewUCStringCopyZ(cx, label.get());
+    if (!labelString) {
+      return false;
+    }
+    RootedValue labelValue(cx, StringValue(labelString));
+    if (!DefineDataProperty(cx, obj, cx->names().label, labelValue)) {
+      return false;
+    }
+  }
+
+  report.setObject(*obj);
+  return true;
+}
+
+// A count type that collects all matching nodes in a bucket.
+class BucketCount : public CountType {
+  struct Count : CountBase {
+    JS::ubi::Vector<JS::ubi::Node::Id> ids_;
+
+    explicit Count(BucketCount& count) : CountBase(count), ids_() {}
+  };
+
+ public:
+  explicit BucketCount() : CountType() {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override {
+    return CountBasePtr(js_new<Count>(*this));
+  }
+  void traceCount(CountBase& countBase, JSTracer* trc) final {}
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+bool BucketCount::count(CountBase& countBase,
+                        mozilla::MallocSizeOf mallocSizeOf, const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+  return count.ids_.append(node.identifier());
+}
+
+bool BucketCount::report(JSContext* cx, CountBase& countBase,
+                         MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+  size_t length = count.ids_.length();
+  Rooted<ArrayObject*> arr(cx, NewDenseFullyAllocatedArray(cx, length));
+  if (!arr) {
+    return false;
+  }
+  arr->ensureDenseInitializedLength(0, length);
+
+  for (size_t i = 0; i < length; i++) {
+    arr->setDenseElement(i, NumberValue(count.ids_[i]));
+  }
+
+  report.setObject(*arr);
+  return true;
+}
+
+// A type that categorizes nodes by their JavaScript type -- 'objects',
+// 'strings', 'scripts', 'domNode', and 'other' -- and then passes the nodes to
+// child types.
+//
+// Implementation details of scripts like jitted code are counted under
+// 'scripts'.
+class ByCoarseType : public CountType {
+  CountTypePtr objects;
+  CountTypePtr scripts;
+  CountTypePtr strings;
+  CountTypePtr other;
+  CountTypePtr domNode;
+
+  struct Count : CountBase {
+    Count(CountType& type, CountBasePtr& objects, CountBasePtr& scripts,
+          CountBasePtr& strings, CountBasePtr& other, CountBasePtr& domNode)
+        : CountBase(type),
+          objects(std::move(objects)),
+          scripts(std::move(scripts)),
+          strings(std::move(strings)),
+          other(std::move(other)),
+          domNode(std::move(domNode)) {}
+
+    CountBasePtr objects;
+    CountBasePtr scripts;
+    CountBasePtr strings;
+    CountBasePtr other;
+    CountBasePtr domNode;
+  };
+
+ public:
+  ByCoarseType(CountTypePtr& objects, CountTypePtr& scripts,
+               CountTypePtr& strings, CountTypePtr& other,
+               CountTypePtr& domNode)
+      : CountType(),
+        objects(std::move(objects)),
+        scripts(std::move(scripts)),
+        strings(std::move(strings)),
+        other(std::move(other)),
+        domNode(std::move(domNode)) {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override;
+  void traceCount(CountBase& countBase, JSTracer* trc) override;
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+CountBasePtr ByCoarseType::makeCount() {
+  CountBasePtr objectsCount(objects->makeCount());
+  CountBasePtr scriptsCount(scripts->makeCount());
+  CountBasePtr stringsCount(strings->makeCount());
+  CountBasePtr otherCount(other->makeCount());
+  CountBasePtr domNodeCount(domNode->makeCount());
+
+  if (!objectsCount || !scriptsCount || !stringsCount || !otherCount ||
+      !domNodeCount) {
+    return CountBasePtr(nullptr);
+  }
+
+  return CountBasePtr(js_new<Count>(*this, objectsCount, scriptsCount,
+                                    stringsCount, otherCount, domNodeCount));
+}
+
+void ByCoarseType::traceCount(CountBase& countBase, JSTracer* trc) {
+  Count& count = static_cast<Count&>(countBase);
+  count.objects->trace(trc);
+  count.scripts->trace(trc);
+  count.strings->trace(trc);
+  count.other->trace(trc);
+  count.domNode->trace(trc);
+}
+
+bool ByCoarseType::count(CountBase& countBase,
+                         mozilla::MallocSizeOf mallocSizeOf, const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+
+  switch (node.coarseType()) {
+    case JS::ubi::CoarseType::Object:
+      return count.objects->count(mallocSizeOf, node);
+    case JS::ubi::CoarseType::Script:
+      return count.scripts->count(mallocSizeOf, node);
+    case JS::ubi::CoarseType::String:
+      return count.strings->count(mallocSizeOf, node);
+    case JS::ubi::CoarseType::Other:
+      return count.other->count(mallocSizeOf, node);
+    case JS::ubi::CoarseType::DOMNode:
+      return count.domNode->count(mallocSizeOf, node);
+    default:
+      MOZ_CRASH("bad JS::ubi::CoarseType in JS::ubi::ByCoarseType::count");
+      return false;
+  }
+}
+
+bool ByCoarseType::report(JSContext* cx, CountBase& countBase,
+                          MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+  Rooted<PlainObject*> obj(cx, NewPlainObject(cx));
+  if (!obj) {
+    return false;
+  }
+
+  RootedValue objectsReport(cx);
+  if (!count.objects->report(cx, &objectsReport) ||
+      !DefineDataProperty(cx, obj, cx->names().objects, objectsReport))
+    return false;
+
+  RootedValue scriptsReport(cx);
+  if (!count.scripts->report(cx, &scriptsReport) ||
+      !DefineDataProperty(cx, obj, cx->names().scripts, scriptsReport))
+    return false;
+
+  RootedValue stringsReport(cx);
+  if (!count.strings->report(cx, &stringsReport) ||
+      !DefineDataProperty(cx, obj, cx->names().strings, stringsReport))
+    return false;
+
+  RootedValue otherReport(cx);
+  if (!count.other->report(cx, &otherReport) ||
+      !DefineDataProperty(cx, obj, cx->names().other, otherReport))
+    return false;
+  RootedValue domReport(cx);
+  if (!count.domNode->report(cx, &domReport) ||
+      !DefineDataProperty(cx, obj, cx->names().domNode, domReport))
+    return false;
+
+  report.setObject(*obj);
+  return true;
+}
+
+// Comparison function for sorting hash table entries by the smallest node ID
+// they counted. Node IDs are stable and unique, which ensures ordering of
+// results never depends on hash table placement or sort algorithm vagaries. The
+// arguments are doubly indirect: they're pointers to elements in an array of
+// pointers to table entries.
+template <typename Entry>
+static int compareEntries(const void* lhsVoid, const void* rhsVoid) {
+  auto lhs = (*static_cast<const Entry* const*>(lhsVoid))
+                 ->value()
+                 ->smallestNodeIdCounted_;
+  auto rhs = (*static_cast<const Entry* const*>(rhsVoid))
+                 ->value()
+                 ->smallestNodeIdCounted_;
+
+  // We don't want to just subtract the values, as they're unsigned.
+  if (lhs < rhs) {
+    return 1;
+  }
+  if (lhs > rhs) {
+    return -1;
+  }
+  return 0;
+}
+
+// A hash map mapping from C strings to counts.
+using CStringCountMap = HashMap<const char*, CountBasePtr,
+                                mozilla::CStringHasher, SystemAllocPolicy>;
+
+// Convert a HashMap into an object with each key one of the entries from the
+// map and each value the associated count's report. For use during census
+// reporting.
+//
+// `Map` must be a `HashMap` from some key type to a `CountBasePtr`.
+//
+// `GetName` must be a callable type which takes `const Map::Key&` and returns
+// `JSAtom*`.
+template <class Map, class GetName>
+static PlainObject* countMapToObject(JSContext* cx, Map& map, GetName getName) {
+  // Build a vector of pointers to entries; sort by total; and then use
+  // that to build the result object. This makes the ordering of entries
+  // more interesting, and a little less non-deterministic.
+
+  JS::ubi::Vector<typename Map::Entry*> entries;
+  if (!entries.reserve(map.count())) {
+    ReportOutOfMemory(cx);
+    return nullptr;
+  }
+
+  for (auto r = map.all(); !r.empty(); r.popFront()) {
+    entries.infallibleAppend(&r.front());
+  }
+
+  if (entries.length()) {
+    qsort(entries.begin(), entries.length(), sizeof(*entries.begin()),
+          compareEntries<typename Map::Entry>);
+  }
+
+  Rooted<PlainObject*> obj(cx, NewPlainObject(cx));
+  if (!obj) {
+    return nullptr;
+  }
+
+  for (auto& entry : entries) {
+    CountBasePtr& thenCount = entry->value();
+    RootedValue thenReport(cx);
+    if (!thenCount->report(cx, &thenReport)) {
+      return nullptr;
+    }
+
+    JSAtom* atom = getName(entry->key());
+    if (!atom) {
+      return nullptr;
+    }
+
+    RootedId entryId(cx, AtomToId(atom));
+    if (!DefineDataProperty(cx, obj, entryId, thenReport)) {
+      return nullptr;
+    }
+  }
+
+  return obj;
+}
+
+// A type that categorizes nodes that are JSObjects by their class name,
+// and places all other nodes in an 'other' category.
+class ByObjectClass : public CountType {
+  // A table mapping class names to their counts. Note that we treat js::Class
+  // instances with the same name as equal keys. If you have several
+  // js::Classes with equal names (and we do; as of this writing there were
+  // six named "Object"), you will get several different js::Classes being
+  // counted in the same table entry.
+  using Table = CStringCountMap;
+  using Entry = Table::Entry;
+
+  struct Count : public CountBase {
+    Table table;
+    CountBasePtr other;
+
+    Count(CountType& type, CountBasePtr& other)
+        : CountBase(type), other(std::move(other)) {}
+  };
+
+  CountTypePtr classesType;
+  CountTypePtr otherType;
+
+ public:
+  ByObjectClass(CountTypePtr& classesType, CountTypePtr& otherType)
+      : CountType(),
+        classesType(std::move(classesType)),
+        otherType(std::move(otherType)) {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override;
+  void traceCount(CountBase& countBase, JSTracer* trc) override;
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+CountBasePtr ByObjectClass::makeCount() {
+  CountBasePtr otherCount(otherType->makeCount());
+  if (!otherCount) {
+    return nullptr;
+  }
+
+  auto count = js::MakeUnique<Count>(*this, otherCount);
+  if (!count) {
+    return nullptr;
+  }
+
+  return CountBasePtr(count.release());
+}
+
+void ByObjectClass::traceCount(CountBase& countBase, JSTracer* trc) {
+  Count& count = static_cast<Count&>(countBase);
+  for (Table::Range r = count.table.all(); !r.empty(); r.popFront()) {
+    r.front().value()->trace(trc);
+  }
+  count.other->trace(trc);
+}
+
+bool ByObjectClass::count(CountBase& countBase,
+                          mozilla::MallocSizeOf mallocSizeOf,
+                          const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+
+  const char* className = node.jsObjectClassName();
+  if (!className) {
+    return count.other->count(mallocSizeOf, node);
+  }
+
+  Table::AddPtr p = count.table.lookupForAdd(className);
+  if (!p) {
+    CountBasePtr classCount(classesType->makeCount());
+    if (!classCount || !count.table.add(p, className, std::move(classCount))) {
+      return false;
+    }
+  }
+  return p->value()->count(mallocSizeOf, node);
+}
+
+bool ByObjectClass::report(JSContext* cx, CountBase& countBase,
+                           MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+  Rooted<PlainObject*> obj(
+      cx, countMapToObject(cx, count.table, [cx](const char* key) {
+        MOZ_ASSERT(key);
+        return Atomize(cx, key, strlen(key));
+      }));
+  if (!obj) {
+    return false;
+  }
+
+  RootedValue otherReport(cx);
+  if (!count.other->report(cx, &otherReport) ||
+      !DefineDataProperty(cx, obj, cx->names().other, otherReport))
+    return false;
+
+  report.setObject(*obj);
+  return true;
+}
+
+class ByDomObjectClass : public CountType {
+  // A table mapping descriptive names to their counts.
+  using UniqueC16String = JS::UniqueTwoByteChars;
+
+  struct UniqueC16StringHasher {
+    using Lookup = UniqueC16String;
+
+    static js::HashNumber hash(const Lookup& lookup) {
+      return mozilla::HashString(lookup.get());
+    }
+
+    static bool match(const UniqueC16String& key, const Lookup& lookup) {
+      return CompareChars(key.get(), js_strlen(key.get()), lookup.get(),
+                          js_strlen(lookup.get())) == 0;
+    }
+  };
+
+  using Table = HashMap<UniqueC16String, CountBasePtr, UniqueC16StringHasher,
+                        SystemAllocPolicy>;
+  using Entry = Table::Entry;
+
+  struct Count : public CountBase {
+    Table table;
+
+    explicit Count(CountType& type) : CountBase(type) {}
+  };
+
+  CountTypePtr classesType;
+
+ public:
+  explicit ByDomObjectClass(CountTypePtr& classesType)
+      : CountType(), classesType(std::move(classesType)) {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override;
+  void traceCount(CountBase& countBase, JSTracer* trc) override;
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+CountBasePtr ByDomObjectClass::makeCount() {
+  auto count = js::MakeUnique<Count>(*this);
+  if (!count) {
+    return nullptr;
+  }
+
+  return CountBasePtr(count.release());
+}
+
+void ByDomObjectClass::traceCount(CountBase& countBase, JSTracer* trc) {
+  Count& count = static_cast<Count&>(countBase);
+  for (Table::Range r = count.table.all(); !r.empty(); r.popFront()) {
+    r.front().value()->trace(trc);
+  }
+}
+
+bool ByDomObjectClass::count(CountBase& countBase,
+                             mozilla::MallocSizeOf mallocSizeOf,
+                             const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+
+  const char16_t* nodeName = node.descriptiveTypeName();
+  if (!nodeName) {
+    return false;
+  }
+
+  UniqueC16String name = DuplicateString(nodeName);
+  if (!name) {
+    return false;
+  }
+
+  Table::AddPtr p = count.table.lookupForAdd(name);
+  if (!p) {
+    CountBasePtr classesCount(classesType->makeCount());
+    if (!classesCount ||
+        !count.table.add(p, std::move(name), std::move(classesCount))) {
+      return false;
+    }
+  }
+  return p->value()->count(mallocSizeOf, node);
+}
+
+bool ByDomObjectClass::report(JSContext* cx, CountBase& countBase,
+                              MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+  Rooted<PlainObject*> obj(
+      cx, countMapToObject(cx, count.table, [cx](const UniqueC16String& key) {
+        const char16_t* chars = key.get();
+        MOZ_ASSERT(chars);
+        return AtomizeChars(cx, chars, js_strlen(chars));
+      }));
+  if (!obj) {
+    return false;
+  }
+
+  report.setObject(*obj);
+  return true;
+}
+
+// A count type that categorizes nodes by their ubi::Node::typeName.
+class ByUbinodeType : public CountType {
+  // Note that, because ubi::Node::typeName promises to return a specific
+  // pointer, not just any string whose contents are correct, we can use their
+  // addresses as hash table keys.
+  using Table = HashMap<const char16_t*, CountBasePtr,
+                        DefaultHasher<const char16_t*>, SystemAllocPolicy>;
+  using Entry = Table::Entry;
+
+  struct Count : public CountBase {
+    Table table;
+
+    explicit Count(CountType& type) : CountBase(type) {}
+  };
+
+  CountTypePtr entryType;
+
+ public:
+  explicit ByUbinodeType(CountTypePtr& entryType)
+      : CountType(), entryType(std::move(entryType)) {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override;
+  void traceCount(CountBase& countBase, JSTracer* trc) override;
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+CountBasePtr ByUbinodeType::makeCount() {
+  auto count = js::MakeUnique<Count>(*this);
+  if (!count) {
+    return nullptr;
+  }
+
+  return CountBasePtr(count.release());
+}
+
+void ByUbinodeType::traceCount(CountBase& countBase, JSTracer* trc) {
+  Count& count = static_cast<Count&>(countBase);
+  for (Table::Range r = count.table.all(); !r.empty(); r.popFront()) {
+    r.front().value()->trace(trc);
+  }
+}
+
+bool ByUbinodeType::count(CountBase& countBase,
+                          mozilla::MallocSizeOf mallocSizeOf,
+                          const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+
+  const char16_t* key = node.typeName();
+  MOZ_ASSERT(key);
+  Table::AddPtr p = count.table.lookupForAdd(key);
+  if (!p) {
+    CountBasePtr typesCount(entryType->makeCount());
+    if (!typesCount || !count.table.add(p, key, std::move(typesCount))) {
+      return false;
+    }
+  }
+  return p->value()->count(mallocSizeOf, node);
+}
+
+bool ByUbinodeType::report(JSContext* cx, CountBase& countBase,
+                           MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+  // Build a vector of pointers to entries; sort by total; and then use
+  // that to build the result object. This makes the ordering of entries
+  // more interesting, and a little less non-deterministic.
+  JS::ubi::Vector<Entry*> entries;
+  if (!entries.reserve(count.table.count())) {
+    return false;
+  }
+  for (Table::Range r = count.table.all(); !r.empty(); r.popFront()) {
+    entries.infallibleAppend(&r.front());
+  }
+  if (entries.length()) {
+    qsort(entries.begin(), entries.length(), sizeof(*entries.begin()),
+          compareEntries<Entry>);
+  }
+
+  // Now build the result by iterating over the sorted vector.
+  Rooted<PlainObject*> obj(cx, NewPlainObject(cx));
+  if (!obj) {
+    return false;
+  }
+  for (Entry** entryPtr = entries.begin(); entryPtr < entries.end();
+       entryPtr++) {
+    Entry& entry = **entryPtr;
+    CountBasePtr& typeCount = entry.value();
+    RootedValue typeReport(cx);
+    if (!typeCount->report(cx, &typeReport)) {
+      return false;
+    }
+
+    const char16_t* name = entry.key();
+    MOZ_ASSERT(name);
+    JSAtom* atom = AtomizeChars(cx, name, js_strlen(name));
+    if (!atom) {
+      return false;
+    }
+    RootedId entryId(cx, AtomToId(atom));
+
+    if (!DefineDataProperty(cx, obj, entryId, typeReport)) {
+      return false;
+    }
+  }
+
+  report.setObject(*obj);
+  return true;
+}
+
+// A count type that categorizes nodes by the JS stack under which they were
+// allocated.
+class ByAllocationStack : public CountType {
+  using Table = HashMap<StackFrame, CountBasePtr, DefaultHasher<StackFrame>,
+                        SystemAllocPolicy>;
+  using Entry = Table::Entry;
+
+  struct Count : public CountBase {
+    // NOTE: You may look up entries in this table by JS::ubi::StackFrame
+    // key only during traversal, NOT ONCE TRAVERSAL IS COMPLETE. Once
+    // traversal is complete, you may only iterate over it.
+    //
+    // In this hash table, keys are JSObjects (with some indirection), and
+    // we use JSObject identity (that is, address identity) as key
+    // identity. The normal way to support such a table is to make the trace
+    // function notice keys that have moved and re-key them in the
+    // table. However, our trace function does *not* rehash; the first GC
+    // may render the hash table unsearchable.
+    //
+    // This is as it should be:
+    //
+    // First, the heap traversal phase needs lookups by key to work. But no
+    // GC may ever occur during a traversal; this is enforced by the
+    // JS::ubi::BreadthFirst template. So the traceCount function doesn't
+    // need to do anything to help traversal; it never even runs then.
+    //
+    // Second, the report phase needs iteration over the table to work, but
+    // never looks up entries by key. GC may well occur during this phase:
+    // we allocate a Map object, and probably cross-compartment wrappers for
+    // SavedFrame instances as well. If a GC were to occur, it would call
+    // our traceCount function; if traceCount were to re-key, that would
+    // ruin the traversal in progress.
+    //
+    // So depending on the phase, we either don't need re-keying, or
+    // can't abide it.
+    Table table;
+    CountBasePtr noStack;
+
+    Count(CountType& type, CountBasePtr& noStack)
+        : CountBase(type), noStack(std::move(noStack)) {}
+  };
+
+  CountTypePtr entryType;
+  CountTypePtr noStackType;
+
+ public:
+  ByAllocationStack(CountTypePtr& entryType, CountTypePtr& noStackType)
+      : CountType(),
+        entryType(std::move(entryType)),
+        noStackType(std::move(noStackType)) {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override;
+  void traceCount(CountBase& countBase, JSTracer* trc) override;
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+CountBasePtr ByAllocationStack::makeCount() {
+  CountBasePtr noStackCount(noStackType->makeCount());
+  if (!noStackCount) {
+    return nullptr;
+  }
+
+  auto count = js::MakeUnique<Count>(*this, noStackCount);
+  if (!count) {
+    return nullptr;
+  }
+  return CountBasePtr(count.release());
+}
+
+void ByAllocationStack::traceCount(CountBase& countBase, JSTracer* trc) {
+  Count& count = static_cast<Count&>(countBase);
+  for (Table::Range r = count.table.all(); !r.empty(); r.popFront()) {
+    // Trace our child Counts.
+    r.front().value()->trace(trc);
+
+    // Trace the StackFrame that is this entry's key. Do not re-key if
+    // it has moved; see comments for ByAllocationStack::Count::table.
+    const StackFrame* key = &r.front().key();
+    auto& k = *const_cast<StackFrame*>(key);
+    k.trace(trc);
+  }
+  count.noStack->trace(trc);
+}
+
+bool ByAllocationStack::count(CountBase& countBase,
+                              mozilla::MallocSizeOf mallocSizeOf,
+                              const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+
+  // If we do have an allocation stack for this node, include it in the
+  // count for that stack.
+  if (node.hasAllocationStack()) {
+    auto allocationStack = node.allocationStack();
+    auto p = count.table.lookupForAdd(allocationStack);
+    if (!p) {
+      CountBasePtr stackCount(entryType->makeCount());
+      if (!stackCount ||
+          !count.table.add(p, allocationStack, std::move(stackCount))) {
+        return false;
+      }
+    }
+    MOZ_ASSERT(p);
+    return p->value()->count(mallocSizeOf, node);
+  }
+
+  // Otherwise, count it in the "no stack" category.
+  return count.noStack->count(mallocSizeOf, node);
+}
+
+bool ByAllocationStack::report(JSContext* cx, CountBase& countBase,
+                               MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+#ifdef DEBUG
+  // Check that nothing rehashes our table while we hold pointers into it.
+  mozilla::Generation generation = count.table.generation();
+#endif
+
+  // Build a vector of pointers to entries; sort by total; and then use
+  // that to build the result object. This makes the ordering of entries
+  // more interesting, and a little less non-deterministic.
+  JS::ubi::Vector<Entry*> entries;
+  if (!entries.reserve(count.table.count())) {
+    return false;
+  }
+  for (Table::Range r = count.table.all(); !r.empty(); r.popFront()) {
+    entries.infallibleAppend(&r.front());
+  }
+  if (entries.length()) {
+    qsort(entries.begin(), entries.length(), sizeof(*entries.begin()),
+          compareEntries<Entry>);
+  }
+
+  // Now build the result by iterating over the sorted vector.
+  Rooted<MapObject*> map(cx, MapObject::create(cx));
+  if (!map) {
+    return false;
+  }
+  for (Entry** entryPtr = entries.begin(); entryPtr < entries.end();
+       entryPtr++) {
+    Entry& entry = **entryPtr;
+    MOZ_ASSERT(entry.key());
+
+    RootedObject stack(cx);
+    if (!entry.key().constructSavedFrameStack(cx, &stack) ||
+        !cx->compartment()->wrap(cx, &stack)) {
+      return false;
+    }
+    RootedValue stackVal(cx, ObjectValue(*stack));
+
+    CountBasePtr& stackCount = entry.value();
+    RootedValue stackReport(cx);
+    if (!stackCount->report(cx, &stackReport)) {
+      return false;
+    }
+
+    if (!MapObject::set(cx, map, stackVal, stackReport)) {
+      return false;
+    }
+  }
+
+  if (count.noStack->total_ > 0) {
+    RootedValue noStackReport(cx);
+    if (!count.noStack->report(cx, &noStackReport)) {
+      return false;
+    }
+    RootedValue noStack(cx, StringValue(cx->names().noStack));
+    if (!MapObject::set(cx, map, noStack, noStackReport)) {
+      return false;
+    }
+  }
+
+  MOZ_ASSERT(generation == count.table.generation());
+
+  report.setObject(*map);
+  return true;
+}
+
+// A count type that categorizes nodes by their script's filename.
+class ByFilename : public CountType {
+  using UniqueCString = JS::UniqueChars;
+
+  struct UniqueCStringHasher {
+    using Lookup = UniqueCString;
+
+    static js::HashNumber hash(const Lookup& lookup) {
+      return mozilla::CStringHasher::hash(lookup.get());
+    }
+
+    static bool match(const UniqueCString& key, const Lookup& lookup) {
+      return mozilla::CStringHasher::match(key.get(), lookup.get());
+    }
+  };
+
+  // A table mapping filenames to their counts. Note that we treat scripts
+  // with the same filename as equivalent. If you have several sources with
+  // the same filename, then all their scripts will get bucketed together.
+  using Table = HashMap<UniqueCString, CountBasePtr, UniqueCStringHasher,
+                        SystemAllocPolicy>;
+  using Entry = Table::Entry;
+
+  struct Count : public CountBase {
+    Table table;
+    CountBasePtr then;
+    CountBasePtr noFilename;
+
+    Count(CountType& type, CountBasePtr&& then, CountBasePtr&& noFilename)
+        : CountBase(type),
+          then(std::move(then)),
+          noFilename(std::move(noFilename)) {}
+  };
+
+  CountTypePtr thenType;
+  CountTypePtr noFilenameType;
+
+ public:
+  ByFilename(CountTypePtr&& thenType, CountTypePtr&& noFilenameType)
+      : CountType(),
+        thenType(std::move(thenType)),
+        noFilenameType(std::move(noFilenameType)) {}
+
+  void destructCount(CountBase& countBase) override {
+    Count& count = static_cast<Count&>(countBase);
+    count.~Count();
+  }
+
+  CountBasePtr makeCount() override;
+  void traceCount(CountBase& countBase, JSTracer* trc) override;
+  bool count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+             const Node& node) override;
+  bool report(JSContext* cx, CountBase& countBase,
+              MutableHandleValue report) override;
+};
+
+CountBasePtr ByFilename::makeCount() {
+  CountBasePtr thenCount(thenType->makeCount());
+  if (!thenCount) {
+    return nullptr;
+  }
+
+  CountBasePtr noFilenameCount(noFilenameType->makeCount());
+  if (!noFilenameCount) {
+    return nullptr;
+  }
+
+  auto count = js::MakeUnique<Count>(*this, std::move(thenCount),
+                                     std::move(noFilenameCount));
+  if (!count) {
+    return nullptr;
+  }
+
+  return CountBasePtr(count.release());
+}
+
+void ByFilename::traceCount(CountBase& countBase, JSTracer* trc) {
+  Count& count = static_cast<Count&>(countBase);
+  for (Table::Range r = count.table.all(); !r.empty(); r.popFront()) {
+    r.front().value()->trace(trc);
+  }
+  count.noFilename->trace(trc);
+}
+
+bool ByFilename::count(CountBase& countBase, mozilla::MallocSizeOf mallocSizeOf,
+                       const Node& node) {
+  Count& count = static_cast<Count&>(countBase);
+
+  const char* filename = node.scriptFilename();
+  if (!filename) {
+    return count.noFilename->count(mallocSizeOf, node);
+  }
+
+  UniqueCString myFilename = DuplicateString(filename);
+  if (!myFilename) {
+    return false;
+  }
+
+  Table::AddPtr p = count.table.lookupForAdd(myFilename);
+  if (!p) {
+    CountBasePtr thenCount(thenType->makeCount());
+    if (!thenCount ||
+        !count.table.add(p, std::move(myFilename), std::move(thenCount))) {
+      return false;
+    }
+  }
+  return p->value()->count(mallocSizeOf, node);
+}
+
+bool ByFilename::report(JSContext* cx, CountBase& countBase,
+                        MutableHandleValue report) {
+  Count& count = static_cast<Count&>(countBase);
+
+  Rooted<PlainObject*> obj(
+      cx, countMapToObject(cx, count.table, [cx](const UniqueCString& key) {
+        const char* utf8chars = key.get();
+        return AtomizeUTF8Chars(cx, utf8chars, strlen(utf8chars));
+      }));
+  if (!obj) {
+    return false;
+  }
+
+  RootedValue noFilenameReport(cx);
+  if (!count.noFilename->report(cx, &noFilenameReport) ||
+      !DefineDataProperty(cx, obj, cx->names().noFilename, noFilenameReport)) {
+    return false;
+  }
+
+  report.setObject(*obj);
+  return true;
+}
+
+/*** Census Handler *********************************************************/
+
+JS_PUBLIC_API bool CensusHandler::operator()(
+    BreadthFirst<CensusHandler>& traversal, Node origin, const Edge& edge,
+    NodeData* referentData, bool first) {
+  // We're only interested in the first time we reach edge.referent, not
+  // in every edge arriving at that node.
+  if (!first) {
+    return true;
+  }
+
+  // Don't count nodes outside the debuggee zones. Do count things in the
+  // special atoms zone, but don't traverse their outgoing edges, on the
+  // assumption that they are shared resources that debuggee is using.
+  // Symbols are always allocated in the atoms zone, even if they were
+  // created for exactly one compartment and never shared; this rule will
+  // include such nodes in the count.
+  const Node& referent = edge.referent;
+  Zone* zone = referent.zone();
+
+  if (census.targetZones.count() == 0 || census.targetZones.has(zone)) {
+    return rootCount->count(mallocSizeOf, referent);
+  }
+
+  if (zone && zone->isAtomsZone()) {
+    traversal.abandonReferent();
+    return rootCount->count(mallocSizeOf, referent);
+  }
+
+  traversal.abandonReferent();
+  return true;
+}
+
+/*** Parsing Breakdowns *****************************************************/
+
+static CountTypePtr ParseChildBreakdown(JSContext* cx, HandleObject breakdown,
+                                        PropertyName* prop) {
+  RootedValue v(cx);
+  if (!GetProperty(cx, breakdown, breakdown, prop, &v)) {
+    return nullptr;
+  }
+  return ParseBreakdown(cx, v);
+}
+
+JS_PUBLIC_API CountTypePtr ParseBreakdown(JSContext* cx,
+                                          HandleValue breakdownValue) {
+  if (breakdownValue.isUndefined()) {
+    // Construct the default type, { by: 'count' }
+    CountTypePtr simple(cx->new_<SimpleCount>());
+    return simple;
+  }
+
+  RootedObject breakdown(cx, ToObject(cx, breakdownValue));
+  if (!breakdown) {
+    return nullptr;
+  }
+
+  RootedValue byValue(cx);
+  if (!GetProperty(cx, breakdown, breakdown, cx->names().by, &byValue)) {
+    return nullptr;
+  }
+  RootedString byString(cx, ToString(cx, byValue));
+  if (!byString) {
+    return nullptr;
+  }
+  Rooted<JSLinearString*> by(cx, byString->ensureLinear(cx));
+  if (!by) {
+    return nullptr;
+  }
+
+  if (StringEqualsLiteral(by, "count")) {
+    RootedValue countValue(cx), bytesValue(cx);
+    if (!GetProperty(cx, breakdown, breakdown, cx->names().count,
+                     &countValue) ||
+        !GetProperty(cx, breakdown, breakdown, cx->names().bytes, &bytesValue))
+      return nullptr;
+
+    // Both 'count' and 'bytes' default to true if omitted, but ToBoolean
+    // naturally treats 'undefined' as false; fix this up.
+    if (countValue.isUndefined()) countValue.setBoolean(true);
+    if (bytesValue.isUndefined()) bytesValue.setBoolean(true);
+
+    // Undocumented feature, for testing: { by: 'count' } breakdowns can have
+    // a 'label' property whose value is converted to a string and included as
+    // a 'label' property on the report object.
+    RootedValue label(cx);
+    if (!GetProperty(cx, breakdown, breakdown, cx->names().label, &label)) {
+      return nullptr;
+    }
+
+    UniqueTwoByteChars labelUnique(nullptr);
+    if (!label.isUndefined()) {
+      RootedString labelString(cx, ToString(cx, label));
+      if (!labelString) {
+        return nullptr;
+      }
+
+      labelUnique = JS_CopyStringCharsZ(cx, labelString);
+      if (!labelUnique) {
+        return nullptr;
+      }
+    }
+
+    CountTypePtr simple(cx->new_<SimpleCount>(
+        labelUnique, ToBoolean(countValue), ToBoolean(bytesValue)));
+    return simple;
+  }
+
+  if (StringEqualsLiteral(by, "bucket")) {
+    return CountTypePtr(cx->new_<BucketCount>());
+  }
+
+  if (StringEqualsLiteral(by, "objectClass")) {
+    CountTypePtr thenType(ParseChildBreakdown(cx, breakdown, cx->names().then));
+    if (!thenType) {
+      return nullptr;
+    }
+
+    CountTypePtr otherType(
+        ParseChildBreakdown(cx, breakdown, cx->names().other));
+    if (!otherType) {
+      return nullptr;
+    }
+
+    return CountTypePtr(cx->new_<ByObjectClass>(thenType, otherType));
+  }
+
+  if (StringEqualsLiteral(by, "coarseType")) {
+    CountTypePtr objectsType(
+        ParseChildBreakdown(cx, breakdown, cx->names().objects));
+    if (!objectsType) {
+      return nullptr;
+    }
+    CountTypePtr scriptsType(
+        ParseChildBreakdown(cx, breakdown, cx->names().scripts));
+    if (!scriptsType) {
+      return nullptr;
+    }
+    CountTypePtr stringsType(
+        ParseChildBreakdown(cx, breakdown, cx->names().strings));
+    if (!stringsType) {
+      return nullptr;
+    }
+    CountTypePtr otherType(
+        ParseChildBreakdown(cx, breakdown, cx->names().other));
+    if (!otherType) {
+      return nullptr;
+    }
+    CountTypePtr domNodeType(
+        ParseChildBreakdown(cx, breakdown, cx->names().domNode));
+    if (!domNodeType) {
+      return nullptr;
+    }
+
+    return CountTypePtr(cx->new_<ByCoarseType>(
+        objectsType, scriptsType, stringsType, otherType, domNodeType));
+  }
+
+  if (StringEqualsLiteral(by, "internalType")) {
+    CountTypePtr thenType(ParseChildBreakdown(cx, breakdown, cx->names().then));
+    if (!thenType) {
+      return nullptr;
+    }
+
+    return CountTypePtr(cx->new_<ByUbinodeType>(thenType));
+  }
+
+  if (StringEqualsLiteral(by, "descriptiveType")) {
+    CountTypePtr thenType(ParseChildBreakdown(cx, breakdown, cx->names().then));
+    if (!thenType) {
+      return nullptr;
+    }
+    return CountTypePtr(cx->new_<ByDomObjectClass>(thenType));
+  }
+
+  if (StringEqualsLiteral(by, "allocationStack")) {
+    CountTypePtr thenType(ParseChildBreakdown(cx, breakdown, cx->names().then));
+    if (!thenType) {
+      return nullptr;
+    }
+    CountTypePtr noStackType(
+        ParseChildBreakdown(cx, breakdown, cx->names().noStack));
+    if (!noStackType) {
+      return nullptr;
+    }
+
+    return CountTypePtr(cx->new_<ByAllocationStack>(thenType, noStackType));
+  }
+
+  if (StringEqualsLiteral(by, "filename")) {
+    CountTypePtr thenType(ParseChildBreakdown(cx, breakdown, cx->names().then));
+    if (!thenType) {
+      return nullptr;
+    }
+
+    CountTypePtr noFilenameType(
+        ParseChildBreakdown(cx, breakdown, cx->names().noFilename));
+    if (!noFilenameType) {
+      return nullptr;
+    }
+
+    return CountTypePtr(
+        cx->new_<ByFilename>(std::move(thenType), std::move(noFilenameType)));
+  }
+
+  // We didn't recognize the breakdown type; complain.
+  UniqueChars byBytes = QuoteString(cx, by, '"');
+  if (!byBytes) {
+    return nullptr;
+  }
+
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                            JSMSG_DEBUG_CENSUS_BREAKDOWN, byBytes.get());
+  return nullptr;
+}
+
+// Get the default census breakdown:
+//
+// { by: "coarseType",
+//   objects: { by: "objectClass" },
+//   other:   { by: "internalType" },
+//   domNode: { by: "descriptiveType" }
+// }
+static CountTypePtr GetDefaultBreakdown(JSContext* cx) {
+  CountTypePtr byDomClass(cx->new_<SimpleCount>());
+  if (!byDomClass) {
+    return nullptr;
+  }
+  CountTypePtr byClass(cx->new_<SimpleCount>());
+  if (!byClass) {
+    return nullptr;
+  }
+
+  CountTypePtr byClassElse(cx->new_<SimpleCount>());
+  if (!byClassElse) {
+    return nullptr;
+  }
+
+  CountTypePtr objects(cx->new_<ByObjectClass>(byClass, byClassElse));
+  if (!objects) {
+    return nullptr;
+  }
+
+  CountTypePtr scripts(cx->new_<SimpleCount>());
+  if (!scripts) {
+    return nullptr;
+  }
+
+  CountTypePtr strings(cx->new_<SimpleCount>());
+  if (!strings) {
+    return nullptr;
+  }
+
+  CountTypePtr byType(cx->new_<SimpleCount>());
+  if (!byType) {
+    return nullptr;
+  }
+
+  CountTypePtr other(cx->new_<ByUbinodeType>(byType));
+  if (!other) {
+    return nullptr;
+  }
+  CountTypePtr domNode(cx->new_<ByDomObjectClass>(byDomClass));
+  if (!domNode) {
+    return nullptr;
+  }
+
+  return CountTypePtr(
+      cx->new_<ByCoarseType>(objects, scripts, strings, other, domNode));
+}
+
+JS_PUBLIC_API bool ParseCensusOptions(JSContext* cx, Census& census,
+                                      HandleObject options,
+                                      CountTypePtr& outResult) {
+  RootedValue breakdown(cx, UndefinedValue());
+  if (options &&
+      !GetProperty(cx, options, options, cx->names().breakdown, &breakdown)) {
+    return false;
+  }
+
+  outResult = breakdown.isUndefined() ? GetDefaultBreakdown(cx)
+                                      : ParseBreakdown(cx, breakdown);
+  return !!outResult;
+}
+
+}  // namespace ubi
+}  // namespace JS