cppgc: Add testing API structure

Adds testing API that can only be used after enabling it on a heap.
The call that enables testing is only provided via v8_for_testing or
cppgc_for_testing build targets which protects against misusing from
production code.

Change-Id: I24a8f5543a2bb479481384e2c555d231383e5d12
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2667513
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72503}

BUILD.gn

@@ -4419,6 +4419,7 @@ v8_component("v8_libbase") {
 
   if (is_tsan && !build_with_chromium) {
     data += [ "tools/sanitizers/tsan_suppressions.txt" ]
+
     # llvm-symbolizer uses libstdc++ from the clang package.
     data += [ "//third_party/llvm-build/Release+Asserts/lib/libstdc++.so.6" ]
   }
@@ -4730,6 +4731,22 @@ v8_source_set("cppgc_base") {
   ]
 }
 
+v8_source_set("cppgc_base_for_testing") {
+  visibility = [ ":*" ]
+
+  sources = [
+    "include/cppgc/testing.h",
+    "src/heap/cppgc/testing.cc",
+  ]
+
+  configs = [
+    ":internal_config",
+    ":cppgc_base_config",
+  ]
+
+  public_deps = [ ":cppgc_base" ]
+}
+
 ###############################################################################
 # Produce a single static library for embedders
 #
@@ -5066,6 +5083,7 @@ if (is_component_build) {
     sources = [ "src/utils/v8dll-main.cc" ]
 
     public_deps = [
+      ":cppgc_base_for_testing",
       ":torque_base",
       ":torque_ls_base",
       ":v8_base",
@@ -5082,12 +5100,11 @@ if (is_component_build) {
   v8_component("cppgc") {
     public_deps = [ ":cppgc_base" ]
 
-    configs = [ ":internal_config" ]
-
     if (!cppgc_is_standalone) {
       deps = [ ":v8" ]
     }
 
+    configs = []
     public_configs = [ ":external_config" ]
   }
 
@@ -5095,9 +5112,12 @@ if (is_component_build) {
     v8_component("cppgc_for_testing") {
       testonly = true
 
-      public_deps = [ ":cppgc_base" ]
+      public_deps = [
+        ":cppgc_base",
+        ":cppgc_base_for_testing",
+      ]
 
-      configs = [ ":internal_config" ]
+      configs = []
       public_configs = [ ":external_config" ]
     }
   }
@@ -5107,7 +5127,7 @@ if (is_component_build) {
 
     public_deps = [ ":v8_cppgc_shared" ]
 
-    configs = [ ":internal_config" ]
+    configs = []
     public_configs = [ ":external_config" ]
   }
 } else {
@@ -5124,6 +5144,7 @@ if (is_component_build) {
     testonly = true
 
     public_deps = [
+      ":cppgc_base_for_testing",
       ":torque_base",
       ":torque_ls_base",
       ":v8_base",
@@ -5148,7 +5169,10 @@ if (is_component_build) {
     group("cppgc_for_testing") {
       testonly = true
 
-      public_deps = [ ":cppgc_base" ]
+      public_deps = [
+        ":cppgc_base",
+        ":cppgc_base_for_testing",
+      ]
 
       public_configs = [ ":external_config" ]
     }

PRESUBMIT.py

@@ -64,6 +64,8 @@ _TEST_CODE_EXCLUDED_PATHS = (
     r'src[\\\/]extensions[\\\/]gc-extension\.cc',
     # Runtime functions used for testing.
     r'src[\\\/]runtime[\\\/]runtime-test\.cc',
+    # Testing helpers.
+    r'src[\\\/]heap[\\\/]cppgc[\\\/]testing\.cc',
 )
 
 

include/cppgc/macros.h

@@ -5,6 +5,8 @@
 #ifndef INCLUDE_CPPGC_MACROS_H_
 #define INCLUDE_CPPGC_MACROS_H_
 
+#include <stddef.h>
+
 #include "cppgc/internal/compiler-specific.h"
 
 namespace cppgc {

include/cppgc/testing.h

@@ -0,0 +1,69 @@
+// Copyright 2021 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.
+
+#ifndef INCLUDE_CPPGC_TESTING_H_
+#define INCLUDE_CPPGC_TESTING_H_
+
+#include "cppgc/common.h"
+#include "cppgc/macros.h"
+#include "v8config.h"  // NOLINT(build/include_directory)
+
+namespace cppgc {
+
+class HeapHandle;
+
+/**
+ * Namespace contains testing helpers.
+
+ * Helpers are only enabled after invoking `Heap::EnableTestingAPIsForTesting()`
+ and will crash otherwise.
+ */
+namespace testing {
+
+/**
+ * Testing helper used to acces heap internals.
+
+ * Only enabled after invoking `EnableTestingAPIsForTesting()`.
+ */
+class V8_EXPORT Heap final {
+ public:
+  /**
+   * Enables testing APIs that can be found in the corresponding `testing`
+   * namespace.
+   *
+   * \param heap_handle
+   */
+  static void EnableTestingAPIsForTesting(HeapHandle& heap_handle);
+};
+
+/**
+ * Overrides the state of the stack with the provided value. Takes precedence
+ * over other parameters that set the stack state. Must no be nested.
+ */
+class V8_EXPORT V8_NODISCARD OverrideEmbedderStackStateScope final {
+  CPPGC_STACK_ALLOCATED();
+
+ public:
+  /**
+   * Constructs a scoped object that automatically enters and leaves the scope.
+   *
+   * \param heap_handle The corresponding heap.
+   */
+  explicit OverrideEmbedderStackStateScope(HeapHandle& heap_handle,
+                                           EmbedderStackState state);
+  ~OverrideEmbedderStackStateScope();
+
+  OverrideEmbedderStackStateScope(const OverrideEmbedderStackStateScope&) =
+      delete;
+  OverrideEmbedderStackStateScope& operator=(
+      const OverrideEmbedderStackStateScope&) = delete;
+
+ private:
+  HeapHandle& heap_handle_;
+};
+
+}  // namespace testing
+}  // namespace cppgc
+
+#endif  // INCLUDE_CPPGC_TESTING_H_

src/heap/cppgc-js/cpp-heap.cc

@@ -261,6 +261,9 @@ void CppHeap::EnterFinalPause(EmbedderStackState stack_state) {
   cppgc::internal::StatsCollector::EnabledScope stats_scope(
       AsBase(), cppgc::internal::StatsCollector::kAtomicMark);
   in_atomic_pause_ = true;
+  if (override_stack_state_) {
+    stack_state = *override_stack_state_;
+  }
   marker_->EnterAtomicPause(stack_state);
   if (compactor_.CancelIfShouldNotCompact(cppgc::Heap::MarkingType::kAtomic,
                                           stack_state)) {

src/heap/cppgc/heap-base.cc

@@ -53,6 +53,20 @@ class ObjectSizeCounter : private HeapVisitor<ObjectSizeCounter> {
 
 }  // namespace
 
+// static
+HeapBase& HeapBase::ForTesting(cppgc::HeapHandle& heap_handle) {
+  auto& heap = From(heap_handle);
+  CHECK(heap.TestingEnabled());
+  return heap;
+}
+
+// static
+const HeapBase& HeapBase::ForTesting(const cppgc::HeapHandle& heap_handle) {
+  const auto& heap = From(heap_handle);
+  CHECK(heap.TestingEnabled());
+  return heap;
+}
+
 HeapBase::HeapBase(
     std::shared_ptr<cppgc::Platform> platform,
     const std::vector<std::unique_ptr<CustomSpaceBase>>& custom_spaces,

src/heap/cppgc/heap-base.h

@@ -36,6 +36,10 @@ class DisallowGarbageCollectionScope;
 class NoGarbageCollectionScope;
 }  // namespace subtle
 
+namespace testing {
+class OverrideEmbedderStackStateScope;
+}  // namespace testing
+
 class Platform;
 
 class V8_EXPORT HeapHandle {
@@ -66,6 +70,9 @@ class V8_EXPORT_PRIVATE HeapBase : public cppgc::HeapHandle {
     return static_cast<const HeapBase&>(heap_handle);
   }
 
+  static HeapBase& ForTesting(cppgc::HeapHandle& heap_handle);
+  static const HeapBase& ForTesting(const cppgc::HeapHandle& heap_handle);
+
   HeapBase(std::shared_ptr<cppgc::Platform> platform,
            const std::vector<std::unique_ptr<CustomSpaceBase>>& custom_spaces,
            StackSupport stack_support,
@@ -153,6 +160,9 @@ class V8_EXPORT_PRIVATE HeapBase : public cppgc::HeapHandle {
   bool in_disallow_gc_scope() const { return disallow_gc_scope_ > 0; }
   bool in_atomic_pause() const { return in_atomic_pause_; }
 
+  void EnableTestingAPIsForTesting() { testing_enabled_ = true; }
+  bool TestingEnabled() const { return testing_enabled_; }
+
  protected:
   virtual void FinalizeIncrementalGarbageCollectionIfNeeded(
       cppgc::Heap::StackState) = 0;
@@ -190,13 +200,16 @@ class V8_EXPORT_PRIVATE HeapBase : public cppgc::HeapHandle {
   size_t disallow_gc_scope_ = 0;
 
   const StackSupport stack_support_;
+  std::unique_ptr<EmbedderStackState> override_stack_state_;
 
   bool in_atomic_pause_ = false;
+  bool testing_enabled_ = false;
 
   friend class MarkerBase::IncrementalMarkingTask;
   friend class testing::TestWithHeap;
   friend class cppgc::subtle::DisallowGarbageCollectionScope;
   friend class cppgc::subtle::NoGarbageCollectionScope;
+  friend class cppgc::testing::OverrideEmbedderStackStateScope;
 };
 
 }  // namespace internal

src/heap/cppgc/heap.cc

@@ -173,12 +173,15 @@ void Heap::FinalizeGarbageCollection(Config::StackState stack_state) {
   DCHECK(!in_no_gc_scope());
   CHECK(!in_disallow_gc_scope());
   config_.stack_state = stack_state;
+  if (override_stack_state_) {
+    config_.stack_state = *override_stack_state_;
+  }
   in_atomic_pause_ = true;
   {
     // This guards atomic pause marking, meaning that no internal method or
     // external callbacks are allowed to allocate new objects.
     cppgc::subtle::DisallowGarbageCollectionScope no_gc_scope(*this);
-    marker_->FinishMarking(stack_state);
+    marker_->FinishMarking(config_.stack_state);
   }
   {
     // Pre finalizers are forbidden from allocating objects.
@@ -189,7 +192,7 @@ void Heap::FinalizeGarbageCollection(Config::StackState stack_state) {
   // TODO(chromium:1056170): replace build flag with dedicated flag.
 #if DEBUG
   MarkingVerifier verifier(*this);
-  verifier.Run(stack_state);
+  verifier.Run(config_.stack_state);
 #endif
 
   subtle::NoGarbageCollectionScope no_gc(*this);

src/heap/cppgc/testing.cc

@@ -0,0 +1,31 @@
+// Copyright 2021 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 "include/cppgc/testing.h"
+
+#include "src/base/logging.h"
+#include "src/heap/cppgc/heap-base.h"
+
+namespace cppgc {
+namespace testing {
+
+void Heap::EnableTestingAPIsForTesting(HeapHandle& heap_handle) {
+  internal::HeapBase::From(heap_handle).EnableTestingAPIsForTesting();
+}
+
+OverrideEmbedderStackStateScope::OverrideEmbedderStackStateScope(
+    HeapHandle& heap_handle, EmbedderStackState state)
+    : heap_handle_(heap_handle) {
+  auto& heap = internal::HeapBase::ForTesting(heap_handle_);
+  CHECK_NULL(heap.override_stack_state_.get());
+  heap.override_stack_state_ = std::make_unique<EmbedderStackState>(state);
+}
+
+OverrideEmbedderStackStateScope::~OverrideEmbedderStackStateScope() {
+  auto& heap = internal::HeapBase::ForTesting(heap_handle_);
+  heap.override_stack_state_.reset();
+}
+
+}  // namespace testing
+}  // namespace cppgc

test/unittests/BUILD.gn

@@ -119,6 +119,7 @@ v8_source_set("cppgc_unittests_sources") {
     "heap/cppgc/sweeper-unittest.cc",
     "heap/cppgc/test-platform.cc",
     "heap/cppgc/test-platform.h",
+    "heap/cppgc/testing-unittest.cc",
     "heap/cppgc/tests.cc",
     "heap/cppgc/tests.h",
     "heap/cppgc/visitor-unittest.cc",

test/unittests/heap/cppgc/testing-unittest.cc

@@ -0,0 +1,62 @@
+// Copyright 2020 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 "include/cppgc/testing.h"
+
+#include "include/cppgc/allocation.h"
+#include "include/cppgc/garbage-collected.h"
+#include "include/cppgc/persistent.h"
+#include "test/unittests/heap/cppgc/tests.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace cppgc {
+namespace internal {
+
+namespace {
+class TestingTest : public testing::TestWithHeap {};
+
+class GCed : public GarbageCollected<GCed> {
+ public:
+  void Trace(Visitor*) const {}
+};
+}  // namespace
+
+TEST_F(TestingTest, EnableTesting) {
+  EXPECT_FALSE(internal::Heap::From(GetHeap())->TestingEnabled());
+  cppgc::testing::Heap::EnableTestingAPIsForTesting(GetHeap()->GetHeapHandle());
+  EXPECT_TRUE(internal::Heap::From(GetHeap())->TestingEnabled());
+}
+
+TEST_F(TestingTest, OverrideEmbedderStackStateScope) {
+  {
+    auto* gced = MakeGarbageCollected<GCed>(GetHeap()->GetAllocationHandle());
+    WeakPersistent<GCed> weak{gced};
+    internal::Heap::From(GetHeap())->CollectGarbage(
+        Heap::Config::PreciseAtomicConfig());
+    EXPECT_FALSE(weak);
+  }
+  cppgc::testing::Heap::EnableTestingAPIsForTesting(GetHeap()->GetHeapHandle());
+  {
+    auto* gced = MakeGarbageCollected<GCed>(GetHeap()->GetAllocationHandle());
+    WeakPersistent<GCed> weak{gced};
+    cppgc::testing::OverrideEmbedderStackStateScope override_stack(
+        GetHeap()->GetHeapHandle(),
+        EmbedderStackState::kMayContainHeapPointers);
+    internal::Heap::From(GetHeap())->CollectGarbage(
+        Heap::Config::PreciseAtomicConfig());
+    EXPECT_TRUE(weak);
+  }
+  {
+    auto* gced = MakeGarbageCollected<GCed>(GetHeap()->GetAllocationHandle());
+    WeakPersistent<GCed> weak{gced};
+    cppgc::testing::OverrideEmbedderStackStateScope override_stack(
+        GetHeap()->GetHeapHandle(), EmbedderStackState::kNoHeapPointers);
+    internal::Heap::From(GetHeap())->CollectGarbage(
+        Heap::Config::ConservativeAtomicConfig());
+    EXPECT_FALSE(weak);
+  }
+}
+
+}  // namespace internal
+}  // namespace cppgc