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 <stdint.h>
+
+#include <functional>
+#include <unordered_map>
+
+#include "components/metrics/leak_detector/leak_analyzer.h"
+#include "components/metrics/leak_detector/stl_allocator.h"
+#include <gperftools/custom_allocator.h>
+
+namespace leak_detector {
+
+// Struct to represent a call stack.
+struct CallStack {
+  static const int kMaxStackDepth = 32;  // Max call stack depth.
+
+  uint32_t depth;                        // Depth of current call stack.
+  const void** stack;                    // Call stack as an array of addrs.
+
+  uint64_t hash;                         // Hash of call stack.
+};
+
+// 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 Hash {
+    long operator() (const CallStack* call_stack) const;

[jar (doing other things), 2015/08/15 03:29:01]

nit: Style: Structs should only be used to hold passive values.  This should
probably be a class.

[Simon Que, 2015/08/15 23:28:30]

Then it would need a "public:" access specifier. I thought the use of a struct
to pass in a Hash to STL containers is pretty standard.

e.g. see KeyHash here:
http://en.cppreference.com/w/cpp/container/unordered_map/unordered_map

Also in existing Chrome code:
https://code.google.com/p/chromium/codesearch#chromium/src/base/containers/ha...

[jar (doing other things), 2015/08/21 02:48:42]

I'm not used to seeing this... but a readability reviewer agreed (subject to not
having C++11 lambda support)....

So you can leave it as is.

Thanks for the correction!

+  };
+
+  CallStackTable(int call_stack_suspicion_threshold);

[jar (doing other things), 2015/08/15 03:29:01]

nit: explicit

[Simon Que, 2015/08/15 23:28:30]

Done.

[Simon Que, 2015/08/18 22:34:04]

Also done in ranked_list.h

+  ~CallStackTable();
+
+  // Add/Remove an allocation for the given call stack.
+  void Add(const CallStack* call_stack);
+  void Remove(const CallStack* call_stack);
+
+  // Dump contents to log buffer |buffer| of size |size|.
+  int Dump(char* buffer, int size) const;

[jar (doing other things), 2015/08/15 03:29:01]

nit: define meaning of return value.

[Simon Que, 2015/08/15 23:28:30]

Done.

+
+  // Check for leak patterns in the allocation data.
+  void TestForLeaks();
+
+  const LeakAnalyzer& leak_analyzer() const {
+    return leak_analyzer_;
+  }
+
+ private:
+  // Hash table entry used to track number of allocs and frees for a call stack.
+  struct Entry {
+    // Number of allocs/frees for the call stack.
+    uint32_t num_allocs;
+    uint32_t num_frees;
+  };
+
+  // The total number of recorded allocations when this object was created. This
+  // acts as a timestamp of sorts.
+  uint64_t total_num_allocs_at_creation_;
+
+  // 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,
+                     Hash,
+                     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  // CALL_STACK_TABLE_H_