Index: lib/sanitizer_common/sanitizer_malloc_introspection_t.h
===================================================================
--- /dev/null
+++ lib/sanitizer_common/sanitizer_malloc_introspection_t.h
@@ -0,0 +1,38 @@
+//===-- sanitizer_malloc_introspect_t.h -------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Provides a sub class of the Darwin malloc_introspection_t struct type so
+// that Sanitizer specific fields can be stored.
+//
+//===----------------------------------------------------------------------===//
+#ifndef SANITIZER_MALLOC_INTROSPECT_T_H
+#define SANITIZER_MALLOC_INTROSPECT_T_H
+#include "sanitizer_common/sanitizer_platform.h"
+
+#if SANITIZER_MAC
+#include <malloc/malloc.h>
+#include "sanitizer_common/sanitizer_internal_defs.h"
+
+namespace __sanitizer {
+
+struct sanitizer_malloc_introspection_t : public malloc_introspection_t {
+  // IMPORTANT: Do not change the order, alignment, or types of these fields to
+  // maintain binary compatibility. You should only add fields to this struct.
+
+  // Used to track changes to the allocator that will affect
+  // zone enumeration.
+  u64 allocator_enumeration_version;
+};
+
+u64 GetMallocZoneAllocatorEnumerationVersion();
+
+}  // namespace __sanitizer
+
+#endif
+#endif
Index: lib/sanitizer_common/sanitizer_malloc_mac.inc
===================================================================
--- lib/sanitizer_common/sanitizer_malloc_mac.inc
+++ lib/sanitizer_common/sanitizer_malloc_mac.inc
@@ -25,14 +25,24 @@
 
 #include "interception/interception.h"
 #include "sanitizer_common/sanitizer_mac.h"
+#include "sanitizer_common/sanitizer_malloc_introspection_t.h"
 
 // Similar code is used in Google Perftools,
 // https://github.com/gperftools/gperftools.
 
 namespace __sanitizer {
+
 extern malloc_zone_t sanitizer_zone;
+
+u64 GetMallocZoneAllocatorEnumerationVersion() {
+  // This represents the current allocator ABI version.
+  // This field should be incremented every time the Allocator
+  // ABI changes in a way that breaks allocator enumeration.
+  return 0;
 }
 
+}  // namespace __sanitizer
+
 INTERCEPTOR(malloc_zone_t *, malloc_create_zone,
                              vm_size_t start_size, unsigned zone_flags) {
   COMMON_MALLOC_ENTER();
@@ -303,7 +313,7 @@
 namespace COMMON_MALLOC_NAMESPACE {
 
 void InitMallocZoneFields() {
-  static malloc_introspection_t sanitizer_zone_introspection;
+  static sanitizer_malloc_introspection_t sanitizer_zone_introspection;
   // Ok to use internal_memset, these places are not performance-critical.
   internal_memset(&sanitizer_zone_introspection, 0,
                   sizeof(sanitizer_zone_introspection));
@@ -318,6 +328,10 @@
   sanitizer_zone_introspection.statistics = &mi_statistics;
   sanitizer_zone_introspection.zone_locked = &mi_zone_locked;
 
+  // Set current allocator enumeration version.
+  sanitizer_zone_introspection.allocator_enumeration_version =
+      GetMallocZoneAllocatorEnumerationVersion();
+
   internal_memset(&sanitizer_zone, 0, sizeof(malloc_zone_t));
 
   // Use version 6 for OSX >= 10.6.