components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/call_stack_table.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 "components/metrics/leak_detector/call_stack_table.h"
+
+#include "components/metrics/leak_detector/call_stack_manager.h"
+
+namespace metrics {
+namespace leak_detector {
+
+namespace {
+
+using ValueType = LeakDetectorValueType;
+
+// During leak analysis, we only want to examine the top
+// |kMaxCountOfSuspciousStacks| entries.
+const int kMaxCountOfSuspciousStacks = 16;
+
+const int kInitialHashTableSize = 1999;
+
+}  // namespace
+
+size_t CallStackTable::StoredHash::operator()(
+    const CallStack* call_stack) const {
+  // The call stack object should already have a hash computed when it was
+  // created.
+  //
+  // This is NOT the actual hash computation function for a new call stack.
+  return call_stack->hash;
+}
+
+CallStackTable::CallStackTable(int call_stack_suspicion_threshold)
+    : num_allocs_(0),
+      num_frees_(0),
+      entry_map_(kInitialHashTableSize),
+      leak_analyzer_(kMaxCountOfSuspciousStacks,
+                     call_stack_suspicion_threshold) {}
+
+CallStackTable::~CallStackTable() {}
+
+void CallStackTable::Add(const CallStack* call_stack) {
+  Entry* entry = &entry_map_[call_stack];
+
+  ++entry->net_num_allocs;
+  ++num_allocs_;
+}
+
+void CallStackTable::Remove(const CallStack* call_stack) {
+  auto iter = entry_map_.find(call_stack);
+  if (iter == entry_map_.end())
+    return;
+  Entry* entry = &iter->second;
+  --entry->net_num_allocs;
+  ++num_frees_;
+
+  // Delete zero-alloc entries to free up space.
+  if (entry->net_num_allocs == 0)
+    entry_map_.erase(iter);
+}
+
+void CallStackTable::TestForLeaks() {
+  // Add all entries to the ranked list.
+  RankedList ranked_list(kMaxCountOfSuspciousStacks);
+
+  for (const auto& entry_pair : entry_map_) {
+    const Entry& entry = entry_pair.second;
+    // Assumes that |entry.net_num_allocs| is always > 0. If that changes
+    // elsewhere in this class, this code should be updated to only pass values
+    // > 0 to |ranked_list|.
+    LeakDetectorValueType call_stack_value(entry_pair.first);
+    ranked_list.Add(call_stack_value, entry.net_num_allocs);
+  }
+  leak_analyzer_.AddSample(ranked_list.Pass());
+}
+
+}  // namespace leak_detector
+}  // namespace metrics