Reland of "Add thread-local allocation context for tracing"

base/trace_event/memory_profiler_allocation_context_unittest.cc

+// Copyright 2015 The Chromium 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 "base/trace_event/memory_profiler_allocation_context.h"
+#include "base/trace_event/trace_event.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+namespace trace_event {
+
+// Define all strings once, because the pseudo stack requires pointer equality,
+// and string interning is unreliable.
+const char* kCupcake = "Cupcake";

[Primiano Tucci (use gerrit), 2015/09/25 16:53:49]

nit: const char kCupcake[] = "Cupcake"; and similar below

+const char* kDonut = "Donut";
+const char* kEclair = "Eclair";
+const char* kFroyo = "Froyo";
+const char* kGingerbread = "Gingerbread";
+const char* kHoneycomb = "Honeycomb";
+
+// Asserts that the fixed-size array |expected_stack| matches the pseudo
+// stack. Syntax note: |const StackFrame (&expected_stack)[N]| is the syntax
+// for "expected_stack is a reference to a const fixed-size array of StackFrame
+// of length N".
+template <size_t N>
+void AssertPseudoStackEquals(const StackFrame(&expected_stack)[N]) {
+  auto pseudo_stack = AllocationContextTracker::GetPseudoStackForTesting();
+  auto actual = pseudo_stack->top();
+  auto actual_bottom = pseudo_stack->bottom();
+  auto expected = expected_stack;
+  auto expected_bottom = expected_stack + N;
+
+  // Note that this requires the pointers to be equal, this is not doing a deep
+  // string comparison.
+  for (; actual != actual_bottom && expected != expected_bottom;
+       actual++, expected++)
+    ASSERT_EQ(*expected, *actual);
+
+  // Ensure that the height of the stacks is the same.
+  ASSERT_EQ(actual, actual_bottom);
+  ASSERT_EQ(expected, expected_bottom);
+}
+
+void AssertPseudoStackEmpty() {
+  auto pseudo_stack = AllocationContextTracker::GetPseudoStackForTesting();
+  ASSERT_EQ(pseudo_stack->top(), pseudo_stack->bottom());
+}
+
+class AllocationContextTest : public testing::Test {
+ public:
+  void EnableTracing() {
+    TraceConfig config("");
+    TraceLog::GetInstance()->SetEnabled(config, TraceLog::RECORDING_MODE);
+    AllocationContextTracker::SetCaptureEnabled(true);
+  }
+
+  void DisableTracing() {
+    AllocationContextTracker::SetCaptureEnabled(false);
+    TraceLog::GetInstance()->SetDisabled();
+  }
+};
+
+TEST_F(AllocationContextTest, PseudoStackScopedTrace) {
+  StackFrame c = kCupcake;

[Primiano Tucci (use gerrit), 2015/09/25 16:53:49]

do you still need this level of indirection?

+  StackFrame d = kDonut;
+  StackFrame e = kEclair;
+  StackFrame f = kFroyo;
+
+  EnableTracing();
+  AssertPseudoStackEmpty();
+
+  {
+    TRACE_EVENT0("Testing", kCupcake);
+    StackFrame frame_c[] = {c};
+    AssertPseudoStackEquals(frame_c);
+
+    {
+      TRACE_EVENT0("Testing", kDonut);
+      StackFrame frame_dc[] = {d, c};
+      AssertPseudoStackEquals(frame_dc);
+    }
+
+    AssertPseudoStackEquals(frame_c);
+
+    {
+      TRACE_EVENT0("Testing", kEclair);
+      StackFrame frame_ec[] = {e, c};
+      AssertPseudoStackEquals(frame_ec);
+    }
+
+    AssertPseudoStackEquals(frame_c);
+  }
+
+  AssertPseudoStackEmpty();
+
+  {
+    TRACE_EVENT0("Testing", kFroyo);
+    StackFrame frame_f[] = {f};
+    AssertPseudoStackEquals(frame_f);
+  }
+
+  AssertPseudoStackEmpty();
+  DisableTracing();
+}
+
+TEST_F(AllocationContextTest, PseudoStackBeginEndTrace) {
+  StackFrame c = kCupcake;
+  StackFrame d = kDonut;
+  StackFrame e = kEclair;
+  StackFrame f = kFroyo;
+
+  StackFrame frame_c[] = {c};
+  StackFrame frame_dc[] = {d, c};
+  StackFrame frame_ec[] = {e, c};
+  StackFrame frame_f[] = {f};
+
+  EnableTracing();
+  AssertPseudoStackEmpty();
+
+  TRACE_EVENT_BEGIN0("Testing", kCupcake);
+  AssertPseudoStackEquals(frame_c);
+
+  TRACE_EVENT_BEGIN0("Testing", kDonut);
+  AssertPseudoStackEquals(frame_dc);
+  TRACE_EVENT_END0("Testing", kDonut);
+
+  AssertPseudoStackEquals(frame_c);
+
+  TRACE_EVENT_BEGIN0("Testing", kEclair);
+  AssertPseudoStackEquals(frame_ec);
+  TRACE_EVENT_END0("Testing", kEclair);
+
+  AssertPseudoStackEquals(frame_c);
+  TRACE_EVENT_END0("Testing", kCupcake);
+
+  AssertPseudoStackEmpty();
+
+  TRACE_EVENT_BEGIN0("Testing", kFroyo);
+  AssertPseudoStackEquals(frame_f);
+  TRACE_EVENT_END0("Testing", kFroyo);
+
+  AssertPseudoStackEmpty();
+  DisableTracing();
+}
+
+TEST_F(AllocationContextTest, PseudoStackMixedTrace) {
+  StackFrame c = kCupcake;
+  StackFrame d = kDonut;
+  StackFrame e = kEclair;
+  StackFrame f = kFroyo;
+
+  StackFrame frame_c[] = {c};
+  StackFrame frame_dc[] = {d, c};
+  StackFrame frame_e[] = {e};
+  StackFrame frame_fe[] = {f, e};
+
+  EnableTracing();
+  AssertPseudoStackEmpty();
+
+  TRACE_EVENT_BEGIN0("Testing", kCupcake);
+  AssertPseudoStackEquals(frame_c);
+
+  {
+    TRACE_EVENT0("Testing", kDonut);
+    AssertPseudoStackEquals(frame_dc);
+  }
+
+  AssertPseudoStackEquals(frame_c);
+  TRACE_EVENT_END0("Testing", kCupcake);
+  AssertPseudoStackEmpty();
+
+  {
+    TRACE_EVENT0("Testing", kEclair);
+    AssertPseudoStackEquals(frame_e);
+
+    TRACE_EVENT_BEGIN0("Testing", kFroyo);
+    AssertPseudoStackEquals(frame_fe);
+    TRACE_EVENT_END0("Testing", kFroyo);
+    AssertPseudoStackEquals(frame_e);
+  }
+
+  AssertPseudoStackEmpty();
+  DisableTracing();
+}
+
+TEST_F(AllocationContextTest, PseudoStackEnableWithEventInScope) {
+  StackFrame h = kHoneycomb;
+
+  {
+    TRACE_EVENT0("Testing", kGingerbread);
+    EnableTracing();
+    AssertPseudoStackEmpty();
+
+    {
+      TRACE_EVENT0("Testing", kHoneycomb);
+      StackFrame frame_h[] = {h};
+      AssertPseudoStackEquals(frame_h);
+    }
+
+    AssertPseudoStackEmpty();
+
+    // The pop at the end of this scope for the 'Gingerbread' frame must not
+    // cause a stack underflow.
+  }
+  AssertPseudoStackEmpty();
+  DisableTracing();
+}
+
+}  // namespace trace_event
+}  // namespace base