diff a/src/hotspot/share/runtime/os.hpp b/src/hotspot/share/runtime/os.hpp
--- a/src/hotspot/share/runtime/os.hpp
+++ b/src/hotspot/share/runtime/os.hpp
@@ -738,10 +738,11 @@
   static void* malloc  (size_t size, MEMFLAGS flags, const NativeCallStack& stack);
   static void* malloc  (size_t size, MEMFLAGS flags);
   static void* realloc (void *memblock, size_t size, MEMFLAGS flag, const NativeCallStack& stack);
   static void* realloc (void *memblock, size_t size, MEMFLAGS flag);
 
+  // handles NULL pointers
   static void  free    (void *memblock);
   static char* strdup(const char *, MEMFLAGS flags = mtInternal);  // Like strdup
   // Like strdup, but exit VM when strdup() returns NULL
   static char* strdup_check_oom(const char*, MEMFLAGS flags = mtInternal);