Index: lib/sanitizer_common/sanitizer_malloc_mac.inc
===================================================================
--- lib/sanitizer_common/sanitizer_malloc_mac.inc
+++ lib/sanitizer_common/sanitizer_malloc_mac.inc
@@ -265,6 +265,13 @@
   return p;
 }
 
+// This public API exists purely for testing purposes.
+extern "C"
+SANITIZER_INTERFACE_ATTRIBUTE
+malloc_zone_t* __sanitizer_mz_default_zone() {
+  return &sanitizer_zone;
+}
+
 // This function is currently unused, and we build with -Werror.
 #if 0
 void __sanitizer_mz_free_definite_size(