components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/leak_detector_impl_unittest.cc

Index: components/metrics/leak_detector/leak_detector_impl_unittest.cc
diff --git a/components/metrics/leak_detector/leak_detector_impl_unittest.cc b/components/metrics/leak_detector/leak_detector_impl_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..810e5f606d2ede81414ef17f2297b63d69d3f291
--- /dev/null
+++ b/components/metrics/leak_detector/leak_detector_impl_unittest.cc
@@ -0,0 +1,461 @@
+// 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.

[bjanakiraman1, 2015/09/01 21:27:27]

Add more comments on what exactly this test is doing (brief explanation).

[Simon Que, 2015/09/01 23:23:31]

Done.

+
+#include "components/metrics/leak_detector/leak_detector_impl.h"
+
+#include <math.h>
+#include <stdint.h>
+
+#include <complex>
+#include <new>
+#include <set>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace leak_detector {
+
+namespace {
+
+// Makes working with complex numbers easier.
+using Complex = std::complex<double>;
+
+// The mapping location in memory for a fictional executable.
+const uintptr_t kMappingAddr = 0x800000;
+const size_t kMappingSize = 0x200000;
+
+// Some call stacks within the fictional executable.
+// * - outside the mapping range, e.g. JIT code.
+const uintptr_t kRawStack0[] = {
+  0x800100,
+  0x900000,
+  0x880080,
+  0x810000,
+};
+const uintptr_t kRawStack1[] = {
+  0x940000,
+  0x980000,
+  0xdeadbeef,  // *
+  0x9a0000,
+};
+const uintptr_t kRawStack2[] = {
+  0x8f0d00,
+  0x803abc,
+  0x9100a0,
+};
+const uintptr_t kRawStack3[] = {
+  0x90fcde,
+  0x900df00d,  // *
+  0x801000,
+  0x880088,
+  0xdeadcafe,  // *
+  0x9f0000,
+  0x8700a0,
+  0x96037c,
+};
+const uintptr_t kRawStack4[] = {
+  0x8c0000,
+  0x85d00d,
+  0x921337,
+  0x780000,  // *
+};
+const uintptr_t kRawStack5[] = {
+  0x990000,
+  0x888888,
+  0x830ac0,
+  0x8e0000,
+  0xc00000,  // *
+};
+
+// This struct makes it easier to pass call stack info to
+// LeakDetectorImplTest::Alloc().
+struct TestCallStack {
+  size_t depth;
+  const void* const* stack;
+};
+
+const TestCallStack kStack0 =
+    { arraysize(kRawStack0), reinterpret_cast<const void* const*>(kRawStack0) };
+const TestCallStack kStack1 =
+    { arraysize(kRawStack1), reinterpret_cast<const void* const*>(kRawStack1) };
+const TestCallStack kStack2 =
+    { arraysize(kRawStack2), reinterpret_cast<const void* const*>(kRawStack2) };
+const TestCallStack kStack3 =
+    { arraysize(kRawStack3), reinterpret_cast<const void* const*>(kRawStack3) };
+const TestCallStack kStack4 =
+    { arraysize(kRawStack4), reinterpret_cast<const void* const*>(kRawStack4) };
+const TestCallStack kStack5 =
+    { arraysize(kRawStack5), reinterpret_cast<const void* const*>(kRawStack5) };
+
+}  // namespace
+
+class LeakDetectorImplTest : public ::testing::Test {

[bjanakiraman1, 2015/09/01 21:27:27]

Add some comments on what methods / classes in the leak detector this is
testing. 

[Simon Que, 2015/09/01 23:23:30]

Done.

+ public:
+  LeakDetectorImplTest()
+      : total_num_allocs_(0),
+        total_num_frees_(0),
+        total_alloced_size_(0),
+        next_analysis_total_alloced_size_(kAllocedSizeAnalysisInterval) {}
+
+  void SetUp() override {
+    CustomAllocator::InitializeForUnitTest();
+
+    const int kSizeSuspicionThreshold = 4;
+    const int kCallStackSuspicionThreshold = 4;
+    detector_.reset(
+        new LeakDetectorImpl(kMappingAddr,
+                             kMappingSize,
+                             kSizeSuspicionThreshold,
+                             kCallStackSuspicionThreshold,
+                             true /* verbose */));
+  }
+
+  void TearDown() override {
+    // Free any memory that was leaked by test cases. Do not use Free() because
+    // that will try to modify |alloced_ptrs_|.
+    for (void* ptr : alloced_ptrs_)
+      delete [] reinterpret_cast<char*>(ptr);
+    alloced_ptrs_.clear();
+
+    // Must destroy all objects using CustomAllocator before shutting it down.
+    detector_.reset();
+    stored_reports_.clear();
+
+    CustomAllocator::Shutdown();
+  }
+
+ protected:
+  // Alloc and free functions that automatically pass allocation info to

[bjanakiraman1, 2015/09/01 21:27:27]

Alloc and free are emulating what tcmalloc hook function does. This is okay, add
some comments to that effect here, 

[Simon Que, 2015/09/01 23:23:30]

Done.

+  // |detector_|.
+  void* Alloc(size_t size, const TestCallStack& stack) {
+    void* ptr = new char[size];
+    detector_->RecordAlloc(ptr, size, stack.depth, stack.stack);
+
+    EXPECT_TRUE(alloced_ptrs_.find(ptr) == alloced_ptrs_.end());
+    alloced_ptrs_.insert(ptr);
+
+    ++total_num_allocs_;
+    total_alloced_size_ += size;
+    if (total_alloced_size_ >= next_analysis_total_alloced_size_) {
+      InternalVector<InternalLeakReport> reports;
+      detector_->TestForLeaks(false /* do_logging */, &reports);
+      for (const InternalLeakReport& report : reports)
+        stored_reports_.insert(report);
+
+      // Determine when the next leak analysis should occur.
+      while (total_alloced_size_ >= next_analysis_total_alloced_size_)
+        next_analysis_total_alloced_size_ += kAllocedSizeAnalysisInterval;
+    }
+    return ptr;
+  }
+
+  // See comment for Alloc().
+  void Free(void* ptr) {
+    auto find_ptr_iter = alloced_ptrs_.find(ptr);
+    EXPECT_FALSE(find_ptr_iter == alloced_ptrs_.end());
+    if (find_ptr_iter == alloced_ptrs_.end())
+      return;
+
+    alloced_ptrs_.erase(find_ptr_iter);
+    detector_->RecordFree(ptr);
+    ++total_num_frees_;
+    delete [] reinterpret_cast<char*>(ptr);
+  }
+
+  // TEST CASE: Julia set fractal computation. Pass in has_leak=true to trigger
+  // the memory leak.
+  void JuliaSet(bool has_leak);
+
+  // Instance of the class being tested.
+  scoped_ptr<LeakDetectorImpl> detector_;
+
+  // Number of pointers allocated and freed so far.
+  size_t total_num_allocs_;
+  size_t total_num_frees_;
+
+  // The interval between consecutive analyses (LeakDetectorImpl::TestForLeaks),
+  // in number of bytes allocated. e.g. if |kAllocedSizeAnalysisInterval| = 1024
+  // then call TestForLeaks() every 1024 bytes of allocation that occur.
+  static const size_t kAllocedSizeAnalysisInterval = 8192;
+
+  // Keeps count of total size allocated by Alloc().
+  size_t total_alloced_size_;
+
+  // The cumulative allocation size at which to trigger the TestForLeaks() call.
+  size_t next_analysis_total_alloced_size_;
+
+  // Stores all pointers to memory allocated by by Alloc() so we can manually
+  // free the leaked pointers at the end.

[bjanakiraman1, 2015/09/01 21:27:27]

Explain why this is present (duplicate bookkeeping). 

[Simon Que, 2015/09/01 23:23:31]

Done.

+  std::set<void*> alloced_ptrs_;
+
+  // Store leak reports here. Use a set so duplicate reports are not stored.
+  std::set<InternalLeakReport> stored_reports_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(LeakDetectorImplTest);
+};
+
+void LeakDetectorImplTest::JuliaSet(bool has_leak) {
+  // The center region of the complex plane that is the basis for our Julia set
+  // computations is a circle of radius kRadius.
+  const static double kRadius = 2;
+
+  // To track points in the complex plane, we will use a rectangular grid in the
+  // range defined by [-kRadius, kRadius] along both axes.
+  const static double kRangeMin = -kRadius;
+  const static double kRangeMax = kRadius;
+
+  // Divide each axis into intervals, each of which is associated with a point
+  // on that axis at its center.
+  const static double kIntervalInverse = 64;
+  const static double kInterval = 1.0 / kIntervalInverse;
+  const static int kNumPoints = (kRangeMax - kRangeMin) / kInterval + 1;
+
+  // Contains some useful functions for converting between points on the complex
+  // plane and in a gridlike data structure.
+  struct ComplexPlane {
+    static int GetXGridIndex(const Complex& value) {
+      return (value.real() + kInterval / 2 - kRangeMin) / kInterval;
+    }
+    static int GetYGridIndex(const Complex& value) {
+      return (value.imag() + kInterval / 2 - kRangeMin) / kInterval;
+    }
+    static Complex GetComplexForGridPoint(size_t x, size_t y) {
+      return Complex(kRangeMin + x * kInterval, kRangeMin + y * kInterval);
+    }
+  };
+
+  // Make sure the choice of interval doesn't result in any loss of precision.
+  ASSERT_EQ(1.0, kInterval * kIntervalInverse);
+
+  // Create a grid for part of the complex plane, with each axis within the
+  // range [kRangeMin, kRangeMax].
+  const size_t width = kNumPoints;
+  const size_t height = kNumPoints;
+  std::vector<Complex*> grid(width * height);
+
+  // Initialize an object for each point within the inner circle |z| < kRadius.
+  for (size_t i = 0; i < width; ++i) {
+    for (size_t j = 0; j < height; ++j) {
+      Complex point = ComplexPlane::GetComplexForGridPoint(i, j);
+      // Do not store any values outside the inner circle.
+      if (abs(point) <= kRadius) {
+        grid[i + j * width] =
+            new(Alloc(sizeof(Complex), kStack0)) Complex(point);
+      }
+    }
+  }
+  EXPECT_LE(alloced_ptrs_.size(), width * height);
+
+  // Create a new grid for the result of the transformation.
+  std::vector<Complex*> next_grid(width * height, nullptr);
+
+  const int kNumIterations = 20;
+  for (int n = 0; n < kNumIterations; ++n) {
+    for (int i = 0; i < kNumPoints; ++i) {
+      for (int j = 0; j < kNumPoints; ++j) {
+        if (!grid[i + j * width])
+          continue;
+
+        // NOTE: The below code is NOT an efficient way to compute a Julia set.
+        // This is only to test the leak detector with some nontrivial code.
+
+        // A simple polynomial function for generating Julia sets is:
+        //   f(z) = z^n + c
+
+        // But in this algorithm, we need the inverse:
+        //   fInv(z) = (z - c)^(1/n)
+
+        // Here, let's use n=5 and c=0.544.
+        const Complex c(0.544, 0);
+        const Complex& z = *grid[i + j * width];
+
+        // This is the principal root.
+        Complex root = pow(z - c, 0.2);
+
+        // Discard the result if it is too far out from the center of the plane.
+        if (abs(root) > kRadius)
+          continue;
+
+        // The below code only allocates Complex objects of the same size. The
+        // leak detector expects various sizes, so increase the allocation size
+        // by a different amount at each call site.
+
+        // Nth root produces N results.
+        // Place all root results on |next_grid|.
+
+        // First, place the principal root.
+        int next_i = ComplexPlane::GetXGridIndex(root);
+        int next_j = ComplexPlane::GetYGridIndex(root);
+        if (!next_grid[next_i + next_j * width]) {
+          next_grid[next_i + next_j * width] =
+              new(Alloc(sizeof(Complex) + 24, kStack1)) Complex(root);
+        }
+
+        double magnitude = abs(root);
+        double angle = arg(root);
+        // To generate other roots, rotate the principal root by increments of
+        // 1/N of a full circle.
+        const double kAngleIncrement = M_PI * 2 / 5;
+
+        // Second root.
+        root = std::polar(magnitude, angle + kAngleIncrement);
+        next_i = ComplexPlane::GetXGridIndex(root);
+        next_j = ComplexPlane::GetYGridIndex(root);
+        if (!next_grid[next_i + next_j * width]) {
+          next_grid[next_i + next_j * width] =
+              new(Alloc(sizeof(Complex) + 40, kStack2)) Complex(root);
+        }
+
+        // In some of the sections below, |has_leak| will trigger a memory leak
+        // by overwriting the old Complex pointer value without freeing it.
+        // Due to the nature of complex roots being confined to equal sections
+        // of the complex plane, each new pointer will displace an old pointer
+        // that was allocated from the same line of code.
+
+        // Third root.
+        root = std::polar(magnitude, angle + kAngleIncrement * 2);
+        next_i = ComplexPlane::GetXGridIndex(root);
+        next_j = ComplexPlane::GetYGridIndex(root);
+        // *** LEAK ***
+        if (has_leak || !next_grid[next_i + next_j * width]) {
+          next_grid[next_i + next_j * width] =
+              new(Alloc(sizeof(Complex) + 40, kStack3)) Complex(root);
+        }
+
+        // Fourth root.
+        root = std::polar(magnitude, angle + kAngleIncrement * 3);
+        next_i = ComplexPlane::GetXGridIndex(root);
+        next_j = ComplexPlane::GetYGridIndex(root);
+        // *** LEAK ***
+        if (has_leak || !next_grid[next_i + next_j * width]) {
+          next_grid[next_i + next_j * width] =
+              new(Alloc(sizeof(Complex) + 52, kStack4)) Complex(root);
+        }
+
+        // Fifth root.
+        root = std::polar(magnitude, angle + kAngleIncrement * 4);
+        next_i = ComplexPlane::GetXGridIndex(root);
+        next_j = ComplexPlane::GetYGridIndex(root);
+        if (!next_grid[next_i + next_j * width]) {
+          next_grid[next_i + next_j * width] =
+              new(Alloc(sizeof(Complex) + 52, kStack5)) Complex(root);
+        }
+      }
+    }
+
+    // Clear the previously allocated points.
+    for (Complex*& point : grid) {
+      if (point) {
+        Free(point);
+        point = nullptr;
+      }
+    }
+
+    // Now swap the two grids for the next iteration.
+    grid.swap(next_grid);
+  }
+
+  // Clear the previously allocated points.
+  for (Complex*& point : grid) {
+    if (point) {
+      Free(point);
+      point = nullptr;
+    }
+  }
+}
+
+TEST_F(LeakDetectorImplTest, CheckTestFramework) {
+  EXPECT_EQ(0U, total_num_allocs_);
+  EXPECT_EQ(0U, total_num_frees_);
+  EXPECT_EQ(0U, alloced_ptrs_.size());
+
+  // Allocate some memory.
+  void* ptr0 = Alloc(12, kStack0);
+  void* ptr1 = Alloc(16, kStack0);
+  void* ptr2 = Alloc(24, kStack0);
+  EXPECT_EQ(3U, total_num_allocs_);
+  EXPECT_EQ(0U, total_num_frees_);
+  EXPECT_EQ(3U, alloced_ptrs_.size());
+
+  // Free one of the pointers.
+  Free(ptr1);
+  EXPECT_EQ(3U, total_num_allocs_);
+  EXPECT_EQ(1U, total_num_frees_);
+  EXPECT_EQ(2U, alloced_ptrs_.size());
+
+  // Allocate some more memory.
+  void* ptr3 = Alloc(72, kStack1);
+  void* ptr4 = Alloc(104, kStack1);
+  void* ptr5 = Alloc(96, kStack1);
+  void* ptr6 = Alloc(24, kStack1);
+  EXPECT_EQ(7U, total_num_allocs_);
+  EXPECT_EQ(1U, total_num_frees_);
+  EXPECT_EQ(6U, alloced_ptrs_.size());
+
+  // Free more pointers.
+  Free(ptr2);
+  Free(ptr4);
+  Free(ptr6);
+  EXPECT_EQ(7U, total_num_allocs_);
+  EXPECT_EQ(4U, total_num_frees_);
+  EXPECT_EQ(3U, alloced_ptrs_.size());
+
+  // Free remaining memory.
+  Free(ptr0);
+  Free(ptr3);
+  Free(ptr5);
+  EXPECT_EQ(7U, total_num_allocs_);
+  EXPECT_EQ(7U, total_num_frees_);
+  EXPECT_EQ(0U, alloced_ptrs_.size());
+}
+
+TEST_F(LeakDetectorImplTest, JuliaSetNoLeak) {
+  JuliaSet(false);

[Simon Que, 2015/09/01 21:09:48]

Comment on flag meaning.

[Simon Que, 2015/09/01 23:23:30]

Done.

+
+  EXPECT_EQ(total_num_allocs_, total_num_frees_);
+  EXPECT_EQ(0U, alloced_ptrs_.size());
+  ASSERT_EQ(0U, stored_reports_.size());
+}
+
+TEST_F(LeakDetectorImplTest, JuliaSetWithLeak) {
+  JuliaSet(true);
+
+  EXPECT_GT(total_num_allocs_, total_num_frees_);
+  EXPECT_GT(alloced_ptrs_.size(), 0U);
+  ASSERT_EQ(2U, stored_reports_.size());
+

[bjanakiraman1, 2015/09/01 21:27:27]

Explain where KrawStack* comes from.

[Simon Que, 2015/09/01 23:23:30]

Done. No longer directly referencing kRawStack* anymore.

+  // The reports should be stored in order of size.
+  const InternalLeakReport& report1 = *stored_reports_.begin();
+  EXPECT_EQ(sizeof(Complex) + 40, report1.alloc_size_bytes);
+  EXPECT_EQ(kStack3.depth, report1.call_stack.size());
+  for (size_t i = 0; i < kStack3.depth && i < report1.call_stack.size(); ++i) {
+    // The call stack's addresses may not fall within the mapping address.
+    // Those that don't will not be converted to mapping offsets.
+    if (kRawStack3[i] >= kMappingAddr &&
+        kRawStack3[i] <= kMappingAddr + kMappingSize) {
+      EXPECT_EQ(kRawStack3[i] - kMappingAddr, report1.call_stack[i]);
+    } else {
+      EXPECT_EQ(kRawStack3[i], report1.call_stack[i]);
+    }
+  }
+
+  const InternalLeakReport& report2 = *(++stored_reports_.begin());
+  EXPECT_EQ(sizeof(Complex) + 52, report2.alloc_size_bytes);
+  EXPECT_EQ(kStack4.depth, report2.call_stack.size());
+  for (size_t i = 0; i < kStack4.depth && i < report2.call_stack.size(); ++i) {
+    // The call stack's addresses may not fall within the mapping address.
+    // Those that don't will not be converted to mapping offsets.
+    if (kRawStack4[i] >= kMappingAddr &&
+        kRawStack4[i] <= kMappingAddr + kMappingSize) {
+      EXPECT_EQ(kRawStack4[i] - kMappingAddr, report2.call_stack[i]);
+    } else {
+      EXPECT_EQ(kRawStack4[i], report2.call_stack[i]);
+    }
+  }
+}
+
+}  // namespace leak_detector