components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/stl_allocator.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_STL_ALLOCATOR_H_
+#define COMPONENTS_METRICS_LEAK_DETECTOR_STL_ALLOCATOR_H_
+
+#include <stddef.h>
+
+#include "base/logging.h"
+
+// Generic allocator class for STL objects
+// that uses a given type-less allocator Alloc, which must provide:
+//   static void* Alloc::Allocate(size_t size);
+//   static void Alloc::Free(void* ptr, size_t size);
+//
+// STL_Allocator<T, MyAlloc> provides the same thread-safety
+// guarantees as MyAlloc.
+//
+// Usage example:
+//   set<T, less<T>, STL_Allocator<T, MyAlloc> > my_set;
+// CAVEAT: Parts of the code below are probably specific
+//         to the STL version(s) we are using.
+//         The code is simply lifted from what std::allocator<> provides.
+template <typename T, class Alloc>
+class STL_Allocator {
+ public:
+  typedef size_t     size_type;
+  typedef ptrdiff_t  difference_type;
+  typedef T*         pointer;
+  typedef const T*   const_pointer;
+  typedef T&         reference;
+  typedef const T&   const_reference;
+  typedef T          value_type;
+
+  template <class T1> struct rebind {
+    typedef STL_Allocator<T1, Alloc> other;
+  };
+
+  STL_Allocator() {}
+  STL_Allocator(const STL_Allocator&) {}
+  template <class T1> STL_Allocator(const STL_Allocator<T1, Alloc>&) {}
+  ~STL_Allocator() {}
+
+  pointer address(reference x) const { return &x; }
+  const_pointer address(const_reference x) const { return &x; }
+
+  pointer allocate(size_type n, const void* = 0) {
+    // Make sure the computation of the total allocation size does not cause an
+    // integer overflow.
+    RAW_CHECK((n * sizeof(T)) / sizeof(T) == n);
+    return static_cast<T*>(Alloc::Allocate(n * sizeof(T)));
+  }
+  void deallocate(pointer p, size_type n) { Alloc::Free(p, n * sizeof(T)); }
+
+  size_type max_size() const { return size_t(-1) / sizeof(T); }
+
+  void construct(pointer p, const T& val) { ::new(p) T(val); }
+  void construct(pointer p) { ::new(p) T(); }
+  void destroy(pointer p) { p->~T(); }
+
+  // There's no state, so these allocators always return the same value.
+  bool operator==(const STL_Allocator&) const { return true; }
+  bool operator!=(const STL_Allocator&) const { return false; }
+};
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_STL_ALLOCATOR_H_