diff --git a/libc/malloc_debug/FreeTrackData.cpp b/libc/malloc_debug/FreeTrackData.cpp
new file mode 100644
index 0000000..3466861
--- /dev/null
+++ b/libc/malloc_debug/FreeTrackData.cpp
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * 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.
+ *
+ * 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.
+ */
+
+#include <stdint.h>
+
+#include "backtrace.h"
+#include "Config.h"
+#include "DebugData.h"
+#include "debug_disable.h"
+#include "debug_log.h"
+#include "FreeTrackData.h"
+#include "malloc_debug.h"
+
+FreeTrackData::FreeTrackData(const Config& config) {
+  cmp_mem_.resize(4096);
+  memset(cmp_mem_.data(), config.fill_free_value, cmp_mem_.size());
+}
+
+void FreeTrackData::LogFreeError(DebugData& debug, const Header* header,
+                                 const uint8_t* pointer) {
+  ScopedDisableDebugCalls disable;
+
+  error_log(LOG_DIVIDER);
+  error_log("+++ ALLOCATION %p USED AFTER FREE", pointer);
+  uint8_t fill_free_value = debug.config().fill_free_value;
+  for (size_t i = 0; i < header->usable_size; i++) {
+    if (pointer[i] != fill_free_value) {
+      error_log("  pointer[%zu] = 0x%02x (expected 0x%02x)", i, pointer[i], fill_free_value);
+    }
+  }
+  if (debug.config().options & BACKTRACE) {
+    BacktraceHeader* back_header = debug.GetFreeBacktrace(header);
+    if (back_header->num_frames > 0) {
+      error_log("Backtrace at time of free:");
+      backtrace_log(&back_header->frames[0], back_header->num_frames);
+    }
+  }
+  error_log(LOG_DIVIDER);
+}
+
+void FreeTrackData::VerifyAndFree(DebugData& debug, const Header* header,
+                                  const void* pointer) {
+  const uint8_t* memory = reinterpret_cast<const uint8_t*>(pointer);
+  size_t bytes = header->usable_size;
+  bytes = (bytes < debug.config().fill_on_free_bytes) ? bytes : debug.config().fill_on_free_bytes;
+  while (bytes > 0) {
+    size_t bytes_to_cmp = (bytes < cmp_mem_.size()) ? bytes : cmp_mem_.size();
+    if (memcmp(memory, cmp_mem_.data(), bytes_to_cmp) != 0) {
+      LogFreeError(debug, header, reinterpret_cast<const uint8_t*>(pointer));
+      break;
+    }
+    bytes -= bytes_to_cmp;
+    memory = &memory[bytes_to_cmp];
+  }
+  g_dispatch->free(header->orig_pointer);
+}
+
+void FreeTrackData::Add(DebugData& debug, const Header* header) {
+  // Make sure the stl calls below don't call the debug_XXX functions.
+  ScopedDisableDebugCalls disable;
+
+  pthread_mutex_lock(&mutex_);
+  if (list_.size() == debug.config().free_track_allocations) {
+    VerifyAndFree(debug, list_.back(), debug.GetPointer(list_.back()));
+    list_.pop_back();
+  }
+
+  list_.push_front(header);
+
+  pthread_mutex_unlock(&mutex_);
+}
+
+void FreeTrackData::VerifyAll(DebugData& debug) {
+  // Make sure the stl calls below don't call the debug_XXX functions.
+  ScopedDisableDebugCalls disable;
+
+  for (const auto& header : list_) {
+    VerifyAndFree(debug, header, debug.GetPointer(header));
+  }
+  list_.clear();
+}