components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/call_stack_table.h

+// 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.
+
+#ifndef COMPONENTS_METRICS_LEAK_DETECTOR_CALL_STACK_TABLE_H_
+#define COMPONENTS_METRICS_LEAK_DETECTOR_CALL_STACK_TABLE_H_
+
+#include <gperftools/custom_allocator.h>
+#include <stdint.h>
+
+#include <functional>
+#include <unordered_map>
+
+#include "components/metrics/leak_detector/leak_analyzer.h"
+#include "components/metrics/leak_detector/stl_allocator.h"
+
+namespace leak_detector {
+
+// Struct to represent a call stack.
+struct CallStack {
+  uint32_t depth;                        // Depth of current call stack.
+  const void** stack;                    // Call stack as an array of addrs.
+
+  size_t hash;                           // Hash of call stack.
+
+  // Generate hash from call stack.
+  struct ComputeHash {
+    size_t operator() (const CallStack* call_stack) const;
+  };
+};
+
+// Contains a hash table where the key is the call stack and the value is the
+// number of allocations from that call stack.
+class CallStackTable {
+ public:
+  struct StoredHash {
+    size_t 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;
+    }
+  };
+
+  explicit CallStackTable(int call_stack_suspicion_threshold);
+  ~CallStackTable();
+
+  // Add/Remove an allocation for the given call stack.
+  // Note that this class does NOT own the CallStack objects. Instead, it
+  // identifies different CallStacks by their hashes.
+  void Add(const CallStack* call_stack);
+  void Remove(const CallStack* call_stack);
+
+  // Dump contents to log buffer |buffer| of size |size|. Returns the number of
+  // bytes remaining in the buffer after writing to it. The number of bytes
+  // remaining includes the zero terminator that was just written, so this will
+  // always return at least 1, unless |size| == 0.
+  size_t Dump(const size_t buffer_size, char* buffer) const;
+
+  // Check for leak patterns in the allocation data.
+  void TestForLeaks();
+
+  const LeakAnalyzer& leak_analyzer() const {
+    return leak_analyzer_;
+  }
+
+  size_t size() const {
+    return entry_map_.size();
+  }
+  bool empty() const {
+    return entry_map_.empty();
+  }
+
+  uint32_t num_allocs() const {
+    return num_allocs_;
+  }
+  uint32_t num_frees() const {
+    return num_frees_;
+  }
+
+ private:
+  // Hash table entry used to track number of allocs and frees for a call stack.
+  struct Entry {
+    // Number of allocs minus number of frees for a given call stack.
+    uint32_t net_num_allocs;
+  };
+
+  // Total number of allocs and frees in this table.
+  uint32_t num_allocs_;
+  uint32_t num_frees_;
+
+  // Hash table containing entries.
+  using TableEntryAllocator =
+      STL_Allocator<std::pair<const CallStack*, Entry>, CustomAllocator>;
+  std::unordered_map<const CallStack*,
+                     Entry,
+                     StoredHash,
+                     std::equal_to<const CallStack*>,
+                     TableEntryAllocator> entry_map_;
+
+  // For detecting leak patterns in incoming allocations.
+  LeakAnalyzer leak_analyzer_;
+
+  DISALLOW_COPY_AND_ASSIGN(CallStackTable);
+};
+
+}  // namespace leak_detector
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_CALL_STACK_TABLE_H_