From 74138b9febd37eac0fc26b8efb110014a83a52c6 Mon Sep 17 00:00:00 2001

From: Jeremy Roman <jbroman@chromium.org>

Date: Wed, 07 Aug 2019 13:26:48 +0000

Subject: [PATCH] WTF: Make LinkedHashSet understand values for which memset initialization would be bad.

Includes a unit test which fails before, and uses this to fix FontCacheKeyTraits.

Bug: 980025

Change-Id: If41f97444c7fd37b9b95d6dadaf3da5689079e9e

Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1739948

Reviewed-by: Kentaro Hara <haraken@chromium.org>

Reviewed-by: Yutaka Hirano <yhirano@chromium.org>

Commit-Queue: Jeremy Roman <jbroman@chromium.org>

Cr-Commit-Position: refs/heads/master@{#684731}

---

diff --git a/third_party/blink/renderer/platform/fonts/font_cache_key.h b/third_party/blink/renderer/platform/fonts/font_cache_key.h

index 0efc8fb..90063cb 100644

--- a/third_party/blink/renderer/platform/fonts/font_cache_key.h

+++ b/third_party/blink/renderer/platform/fonts/font_cache_key.h

@@ -133,6 +133,10 @@

 struct FontCacheKeyTraits : WTF::SimpleClassHashTraits<FontCacheKey> {

   STATIC_ONLY(FontCacheKeyTraits);

+

+  // std::string's empty state need not be zero in all implementations,

+  // and it is held within FontFaceCreationParams.

+  static const bool kEmptyValueIsZero = false;

 };

 }  // namespace blink

diff --git a/third_party/blink/renderer/platform/wtf/linked_hash_set.h b/third_party/blink/renderer/platform/wtf/linked_hash_set.h

index b35b6e9..77e524c 100644

--- a/third_party/blink/renderer/platform/wtf/linked_hash_set.h

+++ b/third_party/blink/renderer/platform/wtf/linked_hash_set.h

@@ -146,6 +146,11 @@

                     LinkedHashSetNodeBase* next)

       : LinkedHashSetNodeBase(prev, next), value_(value) {}

+  LinkedHashSetNode(ValueArg&& value,

+                    LinkedHashSetNodeBase* prev,

+                    LinkedHashSetNodeBase* next)

+      : LinkedHashSetNodeBase(prev, next), value_(std::move(value)) {}

+

   LinkedHashSetNode(LinkedHashSetNode&& other)

       : LinkedHashSetNodeBase(std::move(other)),

         value_(std::move(other.value_)) {}

@@ -445,10 +450,13 @@

   // The slot is empty when the next_ field is zero so it's safe to zero

   // the backing.

-  static const bool kEmptyValueIsZero = true;

+  static const bool kEmptyValueIsZero = ValueTraits::kEmptyValueIsZero;

   static const bool kHasIsEmptyValueFunction = true;

   static bool IsEmptyValue(const Node& node) { return !node.next_; }

+  static Node EmptyValue() {

+    return Node(ValueTraits::EmptyValue(), nullptr, nullptr);

+  }

   static const int kDeletedValue = -1;

diff --git a/third_party/blink/renderer/platform/wtf/list_hash_set_test.cc b/third_party/blink/renderer/platform/wtf/list_hash_set_test.cc

index 4c3f899..cd1be00 100644

--- a/third_party/blink/renderer/platform/wtf/list_hash_set_test.cc

+++ b/third_party/blink/renderer/platform/wtf/list_hash_set_test.cc

@@ -487,6 +487,7 @@

 };

 struct Complicated {

+  Complicated() : Complicated(0) {}

   Complicated(int value) : simple_(value) { objects_constructed_++; }

   Complicated(const Complicated& other) : simple_(other.simple_) {

@@ -495,9 +496,6 @@

   Simple simple_;

   static int objects_constructed_;

-

- private:

-  Complicated() = delete;

 };

 int Complicated::objects_constructed_ = 0;

@@ -731,4 +729,45 @@

 }  // anonymous namespace

+// A unit type which objects to its state being initialized wrong.

+struct InvalidZeroValue {

+  InvalidZeroValue() = default;

+  InvalidZeroValue(WTF::HashTableDeletedValueType) : deleted_(true) {}

+  ~InvalidZeroValue() { CHECK(ok_); }

+  bool IsHashTableDeletedValue() const { return deleted_; }

+

+  bool ok_ = true;

+  bool deleted_ = false;

+};

+

+template <>

+struct HashTraits<InvalidZeroValue> : SimpleClassHashTraits<InvalidZeroValue> {

+  static const bool kEmptyValueIsZero = false;

+};

+

+template <>

+struct DefaultHash<InvalidZeroValue> {

+  struct Hash {

+    static unsigned GetHash(const InvalidZeroValue&) { return 0; }

+    static bool Equal(const InvalidZeroValue&, const InvalidZeroValue&) {

+      return true;

+    }

+  };

+};

+

+template <typename Set>

+class ListOrLinkedHashSetInvalidZeroTest : public testing::Test {};

+

+using InvalidZeroValueSetTypes =

+    testing::Types<ListHashSet<InvalidZeroValue>,

+                   ListHashSet<InvalidZeroValue, 1>,

+                   LinkedHashSet<InvalidZeroValue>>;

+TYPED_TEST_SUITE(ListOrLinkedHashSetInvalidZeroTest, InvalidZeroValueSetTypes);

+

+TYPED_TEST(ListOrLinkedHashSetInvalidZeroTest, InvalidZeroValue) {

+  using Set = TypeParam;

+  Set set;

+  set.insert(InvalidZeroValue());

+}

+

 }  // namespace WTF