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