diff --git a/src/malloc_hook.cc b/src/malloc_hook.cc
new file mode 100644
index 0000000..681d8a2
--- /dev/null
+++ b/src/malloc_hook.cc
@@ -0,0 +1,692 @@
+// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
+// Copyright (c) 2005, Google Inc.
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+// 
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// ---
+// Author: Sanjay Ghemawat <opensource@google.com>
+
+#include <config.h>
+
+// Disable the glibc prototype of mremap(), as older versions of the
+// system headers define this function with only four arguments,
+// whereas newer versions allow an optional fifth argument:
+#ifdef HAVE_MMAP
+# define mremap glibc_mremap
+# include <sys/mman.h>
+# undef mremap
+#endif
+
+#include <stddef.h>
+#ifdef HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#include <algorithm>
+#include "base/logging.h"
+#include "base/spinlock.h"
+#include "maybe_threads.h"
+#include "malloc_hook-inl.h"
+#include <gperftools/malloc_hook.h>
+
+// This #ifdef should almost never be set.  Set NO_TCMALLOC_SAMPLES if
+// you're porting to a system where you really can't get a stacktrace.
+#ifdef NO_TCMALLOC_SAMPLES
+  // We use #define so code compiles even if you #include stacktrace.h somehow.
+# define GetStackTrace(stack, depth, skip)  (0)
+#else
+# include <gperftools/stacktrace.h>
+#endif
+
+// __THROW is defined in glibc systems.  It means, counter-intuitively,
+// "This function will never throw an exception."  It's an optional
+// optimization tool, but we may need to use it to match glibc prototypes.
+#ifndef __THROW    // I guess we're not on a glibc system
+# define __THROW   // __THROW is just an optimization, so ok to make it ""
+#endif
+
+using std::copy;
+
+
+// Declaration of default weak initialization function, that can be overridden
+// by linking-in a strong definition (as heap-checker.cc does).  This is
+// extern "C" so that it doesn't trigger gold's --detect-odr-violations warning,
+// which only looks at C++ symbols.
+//
+// This function is declared here as weak, and defined later, rather than a more
+// straightforward simple weak definition, as a workround for an icc compiler
+// issue ((Intel reference 290819).  This issue causes icc to resolve weak
+// symbols too early, at compile rather than link time.  By declaring it (weak)
+// here, then defining it below after its use, we can avoid the problem.
+extern "C" {
+ATTRIBUTE_WEAK void MallocHook_InitAtFirstAllocation_HeapLeakChecker();
+}
+
+namespace {
+
+void RemoveInitialHooksAndCallInitializers();  // below.
+
+pthread_once_t once = PTHREAD_ONCE_INIT;
+
+// These hooks are installed in MallocHook as the only initial hooks.  The first
+// hook that is called will run RemoveInitialHooksAndCallInitializers (see the
+// definition below) and then redispatch to any malloc hooks installed by
+// RemoveInitialHooksAndCallInitializers.
+//
+// Note(llib): there is a possibility of a race in the event that there are
+// multiple threads running before the first allocation.  This is pretty
+// difficult to achieve, but if it is then multiple threads may concurrently do
+// allocations.  The first caller will call
+// RemoveInitialHooksAndCallInitializers via one of the initial hooks.  A
+// concurrent allocation may, depending on timing either:
+// * still have its initial malloc hook installed, run that and block on waiting
+//   for the first caller to finish its call to
+//   RemoveInitialHooksAndCallInitializers, and proceed normally.
+// * occur some time during the RemoveInitialHooksAndCallInitializers call, at
+//   which point there could be no initial hooks and the subsequent hooks that
+//   are about to be set up by RemoveInitialHooksAndCallInitializers haven't
+//   been installed yet.  I think the worst we can get is that some allocations
+//   will not get reported to some hooks set by the initializers called from
+//   RemoveInitialHooksAndCallInitializers.
+
+void InitialNewHook(const void* ptr, size_t size) {
+  perftools_pthread_once(&once, &RemoveInitialHooksAndCallInitializers);
+  MallocHook::InvokeNewHook(ptr, size);
+}
+
+void InitialPreMMapHook(const void* start,
+                               size_t size,
+                               int protection,
+                               int flags,
+                               int fd,
+                               off_t offset) {
+  perftools_pthread_once(&once, &RemoveInitialHooksAndCallInitializers);
+  MallocHook::InvokePreMmapHook(start, size, protection, flags, fd, offset);
+}
+
+void InitialPreSbrkHook(ptrdiff_t increment) {
+  perftools_pthread_once(&once, &RemoveInitialHooksAndCallInitializers);
+  MallocHook::InvokePreSbrkHook(increment);
+}
+
+// This function is called at most once by one of the above initial malloc
+// hooks.  It removes all initial hooks and initializes all other clients that
+// want to get control at the very first memory allocation.  The initializers
+// may assume that the initial malloc hooks have been removed.  The initializers
+// may set up malloc hooks and allocate memory.
+void RemoveInitialHooksAndCallInitializers() {
+  RAW_CHECK(MallocHook::RemoveNewHook(&InitialNewHook), "");
+  RAW_CHECK(MallocHook::RemovePreMmapHook(&InitialPreMMapHook), "");
+  RAW_CHECK(MallocHook::RemovePreSbrkHook(&InitialPreSbrkHook), "");
+
+  // HeapLeakChecker is currently the only module that needs to get control on
+  // the first memory allocation, but one can add other modules by following the
+  // same weak/strong function pattern.
+  MallocHook_InitAtFirstAllocation_HeapLeakChecker();
+}
+
+}  // namespace
+
+// Weak default initialization function that must go after its use.
+extern "C" void MallocHook_InitAtFirstAllocation_HeapLeakChecker() {
+  // Do nothing.
+}
+
+namespace base { namespace internal {
+
+// This lock is shared between all implementations of HookList::Add & Remove.
+// The potential for contention is very small.  This needs to be a SpinLock and
+// not a Mutex since it's possible for Mutex locking to allocate memory (e.g.,
+// per-thread allocation in debug builds), which could cause infinite recursion.
+static SpinLock hooklist_spinlock(base::LINKER_INITIALIZED);
+
+template <typename T>
+bool HookList<T>::Add(T value_as_t) {
+  AtomicWord value = bit_cast<AtomicWord>(value_as_t);
+  if (value == 0) {
+    return false;
+  }
+  SpinLockHolder l(&hooklist_spinlock);
+  // Find the first slot in data that is 0.
+  int index = 0;
+  while ((index < kHookListMaxValues) &&
+         (base::subtle::NoBarrier_Load(&priv_data[index]) != 0)) {
+    ++index;
+  }
+  if (index == kHookListMaxValues) {
+    return false;
+  }
+  AtomicWord prev_num_hooks = base::subtle::Acquire_Load(&priv_end);
+  base::subtle::NoBarrier_Store(&priv_data[index], value);
+  if (prev_num_hooks <= index) {
+    base::subtle::NoBarrier_Store(&priv_end, index + 1);
+  }
+  return true;
+}
+
+template <typename T>
+void HookList<T>::FixupPrivEndLocked() {
+  AtomicWord hooks_end = base::subtle::NoBarrier_Load(&priv_end);
+  while ((hooks_end > 0) &&
+         (base::subtle::NoBarrier_Load(&priv_data[hooks_end - 1]) == 0)) {
+    --hooks_end;
+  }
+  base::subtle::NoBarrier_Store(&priv_end, hooks_end);
+}
+
+template <typename T>
+bool HookList<T>::Remove(T value_as_t) {
+  if (value_as_t == 0) {
+    return false;
+  }
+  SpinLockHolder l(&hooklist_spinlock);
+  AtomicWord hooks_end = base::subtle::NoBarrier_Load(&priv_end);
+  int index = 0;
+  while (index < hooks_end && value_as_t != bit_cast<T>(
+             base::subtle::NoBarrier_Load(&priv_data[index]))) {
+    ++index;
+  }
+  if (index == hooks_end) {
+    return false;
+  }
+  base::subtle::NoBarrier_Store(&priv_data[index], 0);
+  FixupPrivEndLocked();
+  return true;
+}
+
+template <typename T>
+int HookList<T>::Traverse(T* output_array, int n) const {
+  AtomicWord hooks_end = base::subtle::Acquire_Load(&priv_end);
+  int actual_hooks_end = 0;
+  for (int i = 0; i < hooks_end && n > 0; ++i) {
+    AtomicWord data = base::subtle::Acquire_Load(&priv_data[i]);
+    if (data != 0) {
+      *output_array++ = bit_cast<T>(data);
+      ++actual_hooks_end;
+      --n;
+    }
+  }
+  return actual_hooks_end;
+}
+
+template <typename T>
+T HookList<T>::ExchangeSingular(T value_as_t) {
+  AtomicWord value = bit_cast<AtomicWord>(value_as_t);
+  AtomicWord old_value;
+  SpinLockHolder l(&hooklist_spinlock);
+  old_value = base::subtle::NoBarrier_Load(&priv_data[kHookListSingularIdx]);
+  base::subtle::NoBarrier_Store(&priv_data[kHookListSingularIdx], value);
+  if (value != 0) {
+    base::subtle::NoBarrier_Store(&priv_end, kHookListSingularIdx + 1);
+  } else {
+    FixupPrivEndLocked();
+  }
+  return bit_cast<T>(old_value);
+}
+
+// Initialize a HookList (optionally with the given initial_value in index 0).
+#define INIT_HOOK_LIST { 0 }
+#define INIT_HOOK_LIST_WITH_VALUE(initial_value)                \
+  { 1, { reinterpret_cast<AtomicWord>(initial_value) } }
+
+// Explicit instantiation for malloc_hook_test.cc.  This ensures all the methods
+// are instantiated.
+template struct HookList<MallocHook::NewHook>;
+
+HookList<MallocHook::NewHook> new_hooks_ =
+    INIT_HOOK_LIST_WITH_VALUE(&InitialNewHook);
+HookList<MallocHook::DeleteHook> delete_hooks_ = INIT_HOOK_LIST;
+HookList<MallocHook::PreMmapHook> premmap_hooks_ =
+    INIT_HOOK_LIST_WITH_VALUE(&InitialPreMMapHook);
+HookList<MallocHook::MmapHook> mmap_hooks_ = INIT_HOOK_LIST;
+HookList<MallocHook::MunmapHook> munmap_hooks_ = INIT_HOOK_LIST;
+HookList<MallocHook::MremapHook> mremap_hooks_ = INIT_HOOK_LIST;
+HookList<MallocHook::PreSbrkHook> presbrk_hooks_ =
+    INIT_HOOK_LIST_WITH_VALUE(InitialPreSbrkHook);
+HookList<MallocHook::SbrkHook> sbrk_hooks_ = INIT_HOOK_LIST;
+
+// These lists contain either 0 or 1 hooks.
+HookList<MallocHook::MmapReplacement> mmap_replacement_ = { 0 };
+HookList<MallocHook::MunmapReplacement> munmap_replacement_ = { 0 };
+
+#undef INIT_HOOK_LIST_WITH_VALUE
+#undef INIT_HOOK_LIST
+
+} }  // namespace base::internal
+
+using base::internal::kHookListMaxValues;
+using base::internal::new_hooks_;
+using base::internal::delete_hooks_;
+using base::internal::premmap_hooks_;
+using base::internal::mmap_hooks_;
+using base::internal::mmap_replacement_;
+using base::internal::munmap_hooks_;
+using base::internal::munmap_replacement_;
+using base::internal::mremap_hooks_;
+using base::internal::presbrk_hooks_;
+using base::internal::sbrk_hooks_;
+
+// These are available as C bindings as well as C++, hence their
+// definition outside the MallocHook class.
+extern "C"
+int MallocHook_AddNewHook(MallocHook_NewHook hook) {
+  RAW_VLOG(10, "AddNewHook(%p)", hook);
+  return new_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveNewHook(MallocHook_NewHook hook) {
+  RAW_VLOG(10, "RemoveNewHook(%p)", hook);
+  return new_hooks_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_AddDeleteHook(MallocHook_DeleteHook hook) {
+  RAW_VLOG(10, "AddDeleteHook(%p)", hook);
+  return delete_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveDeleteHook(MallocHook_DeleteHook hook) {
+  RAW_VLOG(10, "RemoveDeleteHook(%p)", hook);
+  return delete_hooks_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_AddPreMmapHook(MallocHook_PreMmapHook hook) {
+  RAW_VLOG(10, "AddPreMmapHook(%p)", hook);
+  return premmap_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemovePreMmapHook(MallocHook_PreMmapHook hook) {
+  RAW_VLOG(10, "RemovePreMmapHook(%p)", hook);
+  return premmap_hooks_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_SetMmapReplacement(MallocHook_MmapReplacement hook) {
+  RAW_VLOG(10, "SetMmapReplacement(%p)", hook);
+  // NOTE this is a best effort CHECK. Concurrent sets could succeed since
+  // this test is outside of the Add spin lock.
+  RAW_CHECK(mmap_replacement_.empty(), "Only one MMapReplacement is allowed.");
+  return mmap_replacement_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveMmapReplacement(MallocHook_MmapReplacement hook) {
+  RAW_VLOG(10, "RemoveMmapReplacement(%p)", hook);
+  return mmap_replacement_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_AddMmapHook(MallocHook_MmapHook hook) {
+  RAW_VLOG(10, "AddMmapHook(%p)", hook);
+  return mmap_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveMmapHook(MallocHook_MmapHook hook) {
+  RAW_VLOG(10, "RemoveMmapHook(%p)", hook);
+  return mmap_hooks_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_AddMunmapHook(MallocHook_MunmapHook hook) {
+  RAW_VLOG(10, "AddMunmapHook(%p)", hook);
+  return munmap_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveMunmapHook(MallocHook_MunmapHook hook) {
+  RAW_VLOG(10, "RemoveMunmapHook(%p)", hook);
+  return munmap_hooks_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_SetMunmapReplacement(MallocHook_MunmapReplacement hook) {
+  RAW_VLOG(10, "SetMunmapReplacement(%p)", hook);
+  // NOTE this is a best effort CHECK. Concurrent sets could succeed since
+  // this test is outside of the Add spin lock.
+  RAW_CHECK(munmap_replacement_.empty(),
+            "Only one MunmapReplacement is allowed.");
+  return munmap_replacement_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveMunmapReplacement(MallocHook_MunmapReplacement hook) {
+  RAW_VLOG(10, "RemoveMunmapReplacement(%p)", hook);
+  return munmap_replacement_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_AddMremapHook(MallocHook_MremapHook hook) {
+  RAW_VLOG(10, "AddMremapHook(%p)", hook);
+  return mremap_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveMremapHook(MallocHook_MremapHook hook) {
+  RAW_VLOG(10, "RemoveMremapHook(%p)", hook);
+  return mremap_hooks_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_AddPreSbrkHook(MallocHook_PreSbrkHook hook) {
+  RAW_VLOG(10, "AddPreSbrkHook(%p)", hook);
+  return presbrk_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemovePreSbrkHook(MallocHook_PreSbrkHook hook) {
+  RAW_VLOG(10, "RemovePreSbrkHook(%p)", hook);
+  return presbrk_hooks_.Remove(hook);
+}
+
+extern "C"
+int MallocHook_AddSbrkHook(MallocHook_SbrkHook hook) {
+  RAW_VLOG(10, "AddSbrkHook(%p)", hook);
+  return sbrk_hooks_.Add(hook);
+}
+
+extern "C"
+int MallocHook_RemoveSbrkHook(MallocHook_SbrkHook hook) {
+  RAW_VLOG(10, "RemoveSbrkHook(%p)", hook);
+  return sbrk_hooks_.Remove(hook);
+}
+
+// The code below is DEPRECATED.
+extern "C"
+MallocHook_NewHook MallocHook_SetNewHook(MallocHook_NewHook hook) {
+  RAW_VLOG(10, "SetNewHook(%p)", hook);
+  return new_hooks_.ExchangeSingular(hook);
+}
+
+extern "C"
+MallocHook_DeleteHook MallocHook_SetDeleteHook(MallocHook_DeleteHook hook) {
+  RAW_VLOG(10, "SetDeleteHook(%p)", hook);
+  return delete_hooks_.ExchangeSingular(hook);
+}
+
+extern "C"
+MallocHook_PreMmapHook MallocHook_SetPreMmapHook(MallocHook_PreMmapHook hook) {
+  RAW_VLOG(10, "SetPreMmapHook(%p)", hook);
+  return premmap_hooks_.ExchangeSingular(hook);
+}
+
+extern "C"
+MallocHook_MmapHook MallocHook_SetMmapHook(MallocHook_MmapHook hook) {
+  RAW_VLOG(10, "SetMmapHook(%p)", hook);
+  return mmap_hooks_.ExchangeSingular(hook);
+}
+
+extern "C"
+MallocHook_MunmapHook MallocHook_SetMunmapHook(MallocHook_MunmapHook hook) {
+  RAW_VLOG(10, "SetMunmapHook(%p)", hook);
+  return munmap_hooks_.ExchangeSingular(hook);
+}
+
+extern "C"
+MallocHook_MremapHook MallocHook_SetMremapHook(MallocHook_MremapHook hook) {
+  RAW_VLOG(10, "SetMremapHook(%p)", hook);
+  return mremap_hooks_.ExchangeSingular(hook);
+}
+
+extern "C"
+MallocHook_PreSbrkHook MallocHook_SetPreSbrkHook(MallocHook_PreSbrkHook hook) {
+  RAW_VLOG(10, "SetPreSbrkHook(%p)", hook);
+  return presbrk_hooks_.ExchangeSingular(hook);
+}
+
+extern "C"
+MallocHook_SbrkHook MallocHook_SetSbrkHook(MallocHook_SbrkHook hook) {
+  RAW_VLOG(10, "SetSbrkHook(%p)", hook);
+  return sbrk_hooks_.ExchangeSingular(hook);
+}
+// End of DEPRECATED code section.
+
+// Note: embedding the function calls inside the traversal of HookList would be
+// very confusing, as it is legal for a hook to remove itself and add other
+// hooks.  Doing traversal first, and then calling the hooks ensures we only
+// call the hooks registered at the start.
+#define INVOKE_HOOKS(HookType, hook_list, args) do {                    \
+    HookType hooks[kHookListMaxValues];                                 \
+    int num_hooks = hook_list.Traverse(hooks, kHookListMaxValues);      \
+    for (int i = 0; i < num_hooks; ++i) {                               \
+      (*hooks[i])args;                                                  \
+    }                                                                   \
+  } while (0)
+
+// There should only be one replacement. Return the result of the first
+// one, or false if there is none.
+#define INVOKE_REPLACEMENT(HookType, hook_list, args) do {              \
+    HookType hooks[kHookListMaxValues];                                 \
+    int num_hooks = hook_list.Traverse(hooks, kHookListMaxValues);      \
+    return (num_hooks > 0 && (*hooks[0])args);                          \
+  } while (0)
+
+
+void MallocHook::InvokeNewHookSlow(const void* p, size_t s) {
+  INVOKE_HOOKS(NewHook, new_hooks_, (p, s));
+}
+
+void MallocHook::InvokeDeleteHookSlow(const void* p) {
+  INVOKE_HOOKS(DeleteHook, delete_hooks_, (p));
+}
+
+void MallocHook::InvokePreMmapHookSlow(const void* start,
+                                       size_t size,
+                                       int protection,
+                                       int flags,
+                                       int fd,
+                                       off_t offset) {
+  INVOKE_HOOKS(PreMmapHook, premmap_hooks_, (start, size, protection, flags, fd,
+                                            offset));
+}
+
+void MallocHook::InvokeMmapHookSlow(const void* result,
+                                    const void* start,
+                                    size_t size,
+                                    int protection,
+                                    int flags,
+                                    int fd,
+                                    off_t offset) {
+  INVOKE_HOOKS(MmapHook, mmap_hooks_, (result, start, size, protection, flags,
+                                       fd, offset));
+}
+
+bool MallocHook::InvokeMmapReplacementSlow(const void* start,
+                                           size_t size,
+                                           int protection,
+                                           int flags,
+                                           int fd,
+                                           off_t offset,
+                                           void** result) {
+  INVOKE_REPLACEMENT(MmapReplacement, mmap_replacement_,
+                      (start, size, protection, flags, fd, offset, result));
+}
+
+void MallocHook::InvokeMunmapHookSlow(const void* p, size_t s) {
+  INVOKE_HOOKS(MunmapHook, munmap_hooks_, (p, s));
+}
+
+bool MallocHook::InvokeMunmapReplacementSlow(const void* p,
+                                             size_t s,
+                                             int* result) {
+  INVOKE_REPLACEMENT(MunmapReplacement, munmap_replacement_, (p, s, result));
+}
+
+void MallocHook::InvokeMremapHookSlow(const void* result,
+                                      const void* old_addr,
+                                      size_t old_size,
+                                      size_t new_size,
+                                      int flags,
+                                      const void* new_addr) {
+  INVOKE_HOOKS(MremapHook, mremap_hooks_, (result, old_addr, old_size, new_size,
+                                           flags, new_addr));
+}
+
+void MallocHook::InvokePreSbrkHookSlow(ptrdiff_t increment) {
+  INVOKE_HOOKS(PreSbrkHook, presbrk_hooks_, (increment));
+}
+
+void MallocHook::InvokeSbrkHookSlow(const void* result, ptrdiff_t increment) {
+  INVOKE_HOOKS(SbrkHook, sbrk_hooks_, (result, increment));
+}
+
+#undef INVOKE_HOOKS
+
+DEFINE_ATTRIBUTE_SECTION_VARS(google_malloc);
+DECLARE_ATTRIBUTE_SECTION_VARS(google_malloc);
+  // actual functions are in debugallocation.cc or tcmalloc.cc
+DEFINE_ATTRIBUTE_SECTION_VARS(malloc_hook);
+DECLARE_ATTRIBUTE_SECTION_VARS(malloc_hook);
+  // actual functions are in this file, malloc_hook.cc, and low_level_alloc.cc
+
+#define ADDR_IN_ATTRIBUTE_SECTION(addr, name) \
+  (reinterpret_cast<uintptr_t>(ATTRIBUTE_SECTION_START(name)) <= \
+     reinterpret_cast<uintptr_t>(addr) && \
+   reinterpret_cast<uintptr_t>(addr) < \
+     reinterpret_cast<uintptr_t>(ATTRIBUTE_SECTION_STOP(name)))
+
+// Return true iff 'caller' is a return address within a function
+// that calls one of our hooks via MallocHook:Invoke*.
+// A helper for GetCallerStackTrace.
+static inline bool InHookCaller(const void* caller) {
+  return ADDR_IN_ATTRIBUTE_SECTION(caller, google_malloc) ||
+         ADDR_IN_ATTRIBUTE_SECTION(caller, malloc_hook);
+  // We can use one section for everything except tcmalloc_or_debug
+  // due to its special linkage mode, which prevents merging of the sections.
+}
+
+#undef ADDR_IN_ATTRIBUTE_SECTION
+
+static bool checked_sections = false;
+
+static inline void CheckInHookCaller() {
+  if (!checked_sections) {
+    INIT_ATTRIBUTE_SECTION_VARS(google_malloc);
+    if (ATTRIBUTE_SECTION_START(google_malloc) ==
+        ATTRIBUTE_SECTION_STOP(google_malloc)) {
+      RAW_LOG(ERROR, "google_malloc section is missing, "
+                     "thus InHookCaller is broken!");
+    }
+    INIT_ATTRIBUTE_SECTION_VARS(malloc_hook);
+    if (ATTRIBUTE_SECTION_START(malloc_hook) ==
+        ATTRIBUTE_SECTION_STOP(malloc_hook)) {
+      RAW_LOG(ERROR, "malloc_hook section is missing, "
+                     "thus InHookCaller is broken!");
+    }
+    checked_sections = true;
+  }
+}
+
+// We can improve behavior/compactness of this function
+// if we pass a generic test function (with a generic arg)
+// into the implementations for GetStackTrace instead of the skip_count.
+extern "C" int MallocHook_GetCallerStackTrace(void** result, int max_depth,
+                                              int skip_count) {
+#if defined(NO_TCMALLOC_SAMPLES)
+  return 0;
+#elif !defined(HAVE_ATTRIBUTE_SECTION_START)
+  // Fall back to GetStackTrace and good old but fragile frame skip counts.
+  // Note: this path is inaccurate when a hook is not called directly by an
+  // allocation function but is daisy-chained through another hook,
+  // search for MallocHook::(Get|Set|Invoke)* to find such cases.
+  return GetStackTrace(result, max_depth, skip_count + int(DEBUG_MODE));
+  // due to -foptimize-sibling-calls in opt mode
+  // there's no need for extra frame skip here then
+#else
+  CheckInHookCaller();
+  // MallocHook caller determination via InHookCaller works, use it:
+  static const int kMaxSkip = 32 + 6 + 3;
+    // Constant tuned to do just one GetStackTrace call below in practice
+    // and not get many frames that we don't actually need:
+    // currently max passsed max_depth is 32,
+    // max passed/needed skip_count is 6
+    // and 3 is to account for some hook daisy chaining.
+  static const int kStackSize = kMaxSkip + 1;
+  void* stack[kStackSize];
+  int depth = GetStackTrace(stack, kStackSize, 1);  // skip this function frame
+  if (depth == 0)   // silenty propagate cases when GetStackTrace does not work
+    return 0;
+  for (int i = 0; i < depth; ++i) {  // stack[0] is our immediate caller
+    if (InHookCaller(stack[i])) {
+      RAW_VLOG(10, "Found hooked allocator at %d: %p <- %p",
+                   i, stack[i], stack[i+1]);
+      i += 1;  // skip hook caller frame
+      depth -= i;  // correct depth
+      if (depth > max_depth) depth = max_depth;
+      copy(stack + i, stack + i + depth, result);
+      if (depth < max_depth  &&  depth + i == kStackSize) {
+        // get frames for the missing depth
+        depth +=
+          GetStackTrace(result + depth, max_depth - depth, 1 + kStackSize);
+      }
+      return depth;
+    }
+  }
+  RAW_LOG(WARNING, "Hooked allocator frame not found, returning empty trace");
+    // If this happens try increasing kMaxSkip
+    // or else something must be wrong with InHookCaller,
+    // e.g. for every section used in InHookCaller
+    // all functions in that section must be inside the same library.
+  return 0;
+#endif
+}
+
+// On systems where we know how, we override mmap/munmap/mremap/sbrk
+// to provide support for calling the related hooks (in addition,
+// of course, to doing what these functions normally do).
+
+#if defined(__linux)
+# include "malloc_hook_mmap_linux.h"
+
+#elif defined(__FreeBSD__)
+# include "malloc_hook_mmap_freebsd.h"
+
+#else
+
+/*static*/void* MallocHook::UnhookedMMap(void *start, size_t length, int prot,
+                                         int flags, int fd, off_t offset) {
+  void* result;
+  if (!MallocHook::InvokeMmapReplacement(
+          start, length, prot, flags, fd, offset, &result)) {
+    result = mmap(start, length, prot, flags, fd, offset);
+  }
+  return result;
+}
+
+/*static*/int MallocHook::UnhookedMUnmap(void *start, size_t length) {
+  int result;
+  if (!MallocHook::InvokeMunmapReplacement(start, length, &result)) {
+    result = munmap(start, length);
+  }
+  return result;
+}
+
+#endif