# define _XBT_GNUC_FORMAT( arg_idx ) \
__attribute__((__format_arg__ (arg_idx)))
# define _XBT_GNUC_NORETURN __attribute__((__noreturn__))
-# define _XBT_GNUC_UNUSED __attribute__((unused))
+# define _XBT_GNUC_UNUSED __attribute__((__unused__))
# define _XBT_GNUC_CONSTRUCTOR __attribute__((__constructor__))
# define _XBT_GNUC_DESTRUCTOR __attribute__((__destructor__))
# undef _XBT_NEED_INIT_PRAGMA