Issue #3391 - Add detached initialization class

test/plugin/DetachedInitializationTest.cpp

Index: test/plugin/DetachedInitializationTest.cpp
===================================================================
new file mode 100644
--- /dev/null
+++ b/test/plugin/DetachedInitializationTest.cpp
@@ -0,0 +1,198 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2016 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <exception>
+#include <gtest/gtest.h>
+#include "../../src/plugin/DetachedInitialization.h"
+
+// Initializer that does nothing
+void NullFunction()
+{}
+
+// Initializer that always throws
+const std::string failMessage = "initializer failed on purpose";
+void FailFunction()
+{
+  throw std::runtime_error(failMessage);
+}
+
+/*
+ * The destructor has to be able to block to wait for the initializer
+ * This test ensures that it doesn't block unnecessarily.
+ */
+TEST(DetachedInitializer, DestructorDoesNotBlockAfterNoActivity)
+{
+  DetachedInitializer<NullFunction> x;
+}
+
+TEST(DetachedInitializer, NullInstance)
+{
+  ASSERT_NO_THROW(
+    {
+      DetachedInitializer<NullFunction> x;
+      x.SpawnInitializer();
+      x.EnsureInitialized();
+    }
+  );
+}
+
+/*
+ * This test illustrates a defect in Google Test.
+ * This test fails with a message that the test threw an exception.
+ * The exception message is the one thrown by FailFunction.
+ * It does not fail, importantly, because SpawnInitializer() throws.
+ * This can be verified in the debugger.
+ *
+ * It's disabled in the present code base so it doesn't break the unit test.
+ * Check this test again when we upgrade past GTest 1.60 and the VS 2012 toolset.
+ */
+TEST(DetachedInitializer, DISABLED_EnsureInitializedThrowingGtestDefectIllustration)
+{
+  DetachedInitializer<FailFunction> x;
+  bool threw = false;
+  try
+  {
+    x.SpawnInitializer();
+  }
+  catch (...)
+  {
+    threw = true;
+    FAIL() << "SpawnInitializer() threw";
+  }
+  ASSERT_FALSE(threw);
+}
+
+/*
+ * This test fails because of a defect in Google Test.
+ * It's disabled at present, but should be enabled when the previous test is working.
+ */
+TEST(DetachedInitializer, DISABLED_EnsureInitializedThrowing)
+{
+  DetachedInitializer<FailFunction> x;
+  try
+  {
+    x.SpawnInitializer();
+  }
+  catch (...)
+  {
+    FAIL() << "SpawnInitializer() threw";
+    return;
+  }
+  try
+  {
+    x.EnsureInitialized();
+    FAIL() << "EnsureInitialized() did not throw";
+  }
+  catch (std::runtime_error& e)
+  {
+    ASSERT_EQ(failMessage, e.what());
+  }
+}
+
+/*
+ * Resetable version of DetachedInitializer
+ */
+template<void(&F)()>
+class DidReset
+  : public DetachedInitializer<F>
+{
+public:
+  void Reset()
+  {
+    isInitializationComplete.store(false, std::memory_order_relaxed);
+    hasInitializerStarted.store(false, std::memory_order_relaxed);
+    initializerException = nullptr;
+    // Lock and unlock the mutex to clear any previous state
+    // It will also detect a locked mutex left over from a previous test.
+    mutex.lock();
+    mutex.unlock();
+  }
+};
+
+/*
+ * Uses designated implementation pattern of DetachedInitializer
+ */
+struct DeferredIncrementingInitializer
+{
+  static int initializedCount;
+
+  static void Incrementer()
+  {
+    ++initializedCount;
+  }
+
+  typedef DidReset<Incrementer> InitializerType;
+  static InitializerType di;
+
+public:
+  DeferredIncrementingInitializer()
+  {
+    di.SpawnInitializer();
+  }
+
+  static void ResetClass()
+  {
+    initializedCount = 0;
+    di.Reset();
+  }
+
+  static int GetInitializerCount ()
+  {
+    di.EnsureInitialized();
+    return initializedCount;
+  }
+};
+DeferredIncrementingInitializer::InitializerType DeferredIncrementingInitializer::di;
+int DeferredIncrementingInitializer::initializedCount = 0;
+
+TEST(DetachedInitializer, Single)
+{
+  DeferredIncrementingInitializer::ResetClass();
+  DeferredIncrementingInitializer x;
+  ASSERT_EQ(1, DeferredIncrementingInitializer::GetInitializerCount());
+}
+
+TEST(DetachedInitializer, Two)
+{
+  DeferredIncrementingInitializer::ResetClass();
+  DeferredIncrementingInitializer x;
+  DeferredIncrementingInitializer y;
+  ASSERT_EQ(1, DeferredIncrementingInitializer::GetInitializerCount());
+}
+
+/*
+ * This test implicitly calls EnsureInitialized before the second call to SpawnInitializer.
+ */
+TEST(DetachedInitializer, TwoInterleaved)
+{
+  DeferredIncrementingInitializer::ResetClass();
+  DeferredIncrementingInitializer x;
+  EXPECT_EQ(1, DeferredIncrementingInitializer::GetInitializerCount());
+  DeferredIncrementingInitializer y;
+  ASSERT_EQ(1, DeferredIncrementingInitializer::GetInitializerCount());
+}
+
+TEST(DetachedInitializer, Many)
+{
+  DeferredIncrementingInitializer::ResetClass();
+  const int many = 1000000;
+  for (int j = 0; j < many;++j)
+  {
+    DeferredIncrementingInitializer x;
+  }
+  ASSERT_EQ(1, DeferredIncrementingInitializer::GetInitializerCount());
+}