[heap] Create a thin wrapper around wrapper tracing in V8 to avoid misuse

test/unittests/heap/embedder-tracing-unittest.cc

Index: test/unittests/heap/embedder-tracing-unittest.cc
diff --git a/test/unittests/heap/embedder-tracing-unittest.cc b/test/unittests/heap/embedder-tracing-unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0b321ef4cc0e6e7dc4ec98467ff6b820a0e24467
--- /dev/null
+++ b/test/unittests/heap/embedder-tracing-unittest.cc
@@ -0,0 +1,165 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/heap/embedder-tracing.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace v8 {
+namespace internal {
+namespace heap {
+
+using testing::StrictMock;
+using testing::_;
+using testing::Return;
+using v8::EmbedderHeapTracer;
+using v8::internal::LocalEmbedderHeapTracer;
+
+namespace {
+
+LocalEmbedderHeapTracer::WrapperInfo CreateWrapperInfo() {
+  return LocalEmbedderHeapTracer::WrapperInfo(nullptr, nullptr);
+}
+
+}  // namespace
+
+class MockEmbedderHeapTracer : public EmbedderHeapTracer {
+ public:
+  MOCK_METHOD0(TracePrologue, void());
+  MOCK_METHOD0(TraceEpilogue, void());
+  MOCK_METHOD0(AbortTracing, void());
+  MOCK_METHOD0(EnterFinalPause, void());
+  MOCK_METHOD0(NumberOfWrappersToTrace, size_t());
+  MOCK_METHOD1(RegisterV8References,
+               void(const std::vector<std::pair<void*, void*> >&));
+  MOCK_METHOD2(AdvanceTracing,
+               bool(double deadline_in_ms, AdvanceTracingActions actions));
+};
+
+TEST(LocalEmbedderHeapTracer, InUse) {
+  LocalEmbedderHeapTracer local_tracer;
+  MockEmbedderHeapTracer mock_remote_tracer;
+  local_tracer.SetRemoteTracer(&mock_remote_tracer);
+  EXPECT_TRUE(local_tracer.InUse());
+}
+
+TEST(LocalEmbedderHeapTracer, NoRemoteTracer) {
+  LocalEmbedderHeapTracer local_tracer;
+  // We should be able to call all functions without a remote tracer being
+  // attached.
+  EXPECT_FALSE(local_tracer.InUse());
+  local_tracer.TracePrologue();
+  local_tracer.EnterFinalPause();
+  bool more_work = local_tracer.Trace(
+      0, EmbedderHeapTracer::AdvanceTracingActions(
+             EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
+  EXPECT_FALSE(more_work);
+  local_tracer.TraceEpilogue();
+}
+
+TEST(LocalEmbedderHeapTracer, TracePrologueForwards) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  EXPECT_CALL(remote_tracer, TracePrologue());
+  local_tracer.TracePrologue();
+}
+
+TEST(LocalEmbedderHeapTracer, TraceEpilogueForwards) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  EXPECT_CALL(remote_tracer, TraceEpilogue());
+  local_tracer.TraceEpilogue();
+}
+
+TEST(LocalEmbedderHeapTracer, AbortTracingForwards) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  EXPECT_CALL(remote_tracer, AbortTracing());
+  local_tracer.AbortTracing();
+}
+
+TEST(LocalEmbedderHeapTracer, AbortTracingClearsCachedWrappers) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  local_tracer.AddWrapperToTrace(CreateWrapperInfo());
+  EXPECT_CALL(remote_tracer, AbortTracing());
+  local_tracer.AbortTracing();
+  EXPECT_EQ(0u, local_tracer.NumberOfCachedWrappersToTrace());
+}
+
+TEST(LocalEmbedderHeapTracer, EnterFinalPauseForwards) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  EXPECT_CALL(remote_tracer, EnterFinalPause());
+  local_tracer.EnterFinalPause();
+}
+
+TEST(LocalEmbedderHeapTracer, NumberOfWrappersToTraceIncludesRemote) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  EXPECT_CALL(remote_tracer, NumberOfWrappersToTrace());
+  local_tracer.NumberOfWrappersToTrace();
+}
+
+TEST(LocalEmbedderHeapTracer, NumberOfCachedWrappersToTraceExcludesRemote) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  local_tracer.NumberOfCachedWrappersToTrace();
+}
+
+TEST(LocalEmbedderHeapTracer, RegisterWrappersWithRemoteTracer) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  local_tracer.AddWrapperToTrace(CreateWrapperInfo());
+  EXPECT_EQ(1u, local_tracer.NumberOfCachedWrappersToTrace());
+  EXPECT_CALL(remote_tracer, RegisterV8References(_));
+  local_tracer.RegisterWrappersWithRemoteTracer();
+  EXPECT_EQ(0u, local_tracer.NumberOfCachedWrappersToTrace());
+  EXPECT_CALL(remote_tracer, NumberOfWrappersToTrace()).WillOnce(Return(1));
+  EXPECT_EQ(1u, local_tracer.NumberOfWrappersToTrace());
+}
+
+TEST(LocalEmbedderHeapTracer, TraceFinishes) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  local_tracer.AddWrapperToTrace(CreateWrapperInfo());
+  EXPECT_EQ(1u, local_tracer.NumberOfCachedWrappersToTrace());
+  EXPECT_CALL(remote_tracer, RegisterV8References(_));
+  EXPECT_CALL(remote_tracer, AdvanceTracing(0, _)).WillOnce(Return(false));
+  EXPECT_EQ(
+      false,
+      local_tracer.Trace(
+          0, EmbedderHeapTracer::AdvanceTracingActions(
+                 EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION)));
+  EXPECT_EQ(0u, local_tracer.NumberOfCachedWrappersToTrace());
+}
+
+TEST(LocalEmbedderHeapTracer, TraceDoesNotFinish) {
+  LocalEmbedderHeapTracer local_tracer;
+  StrictMock<MockEmbedderHeapTracer> remote_tracer;
+  local_tracer.SetRemoteTracer(&remote_tracer);
+  local_tracer.AddWrapperToTrace(CreateWrapperInfo());
+  EXPECT_EQ(1u, local_tracer.NumberOfCachedWrappersToTrace());
+  EXPECT_CALL(remote_tracer, RegisterV8References(_));
+  EXPECT_CALL(remote_tracer, AdvanceTracing(0, _)).WillOnce(Return(true));
+  EXPECT_EQ(
+      true,
+      local_tracer.Trace(
+          0, EmbedderHeapTracer::AdvanceTracingActions(
+                 EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION)));
+  EXPECT_EQ(0u, local_tracer.NumberOfCachedWrappersToTrace());
+}
+
+}  // namespace heap
+}  // namespace internal
+}  // namespace v8