Used as an input or output parameter.

   Returns a character string, which always includes the terminating
   null character \0.  The DCE RPC runtime allocates memory for the
   returned string.  The application calls the rpc_string_free()
   routine to deallocate the memory occupied by the string.

   If there is no data for the requested string, the routine returns
   the string \0.  For example, if the string binding passed to
   routine rpc_string_binding_parse() does not contain an object UUID,
   the routine returns \0 as the value of the object UUID string.  The
   application must call the rpc_string_free() routine to deallocate
   the memory occupied by this string.

   If an application does not require a returned output string, the
   application specifies NULL for this parameter.