# cpp test.c -o test.lst
In file included from /usr/include/features.h:283,
                 from /usr/include/stdio.h:27,
                 from test.c:1:
/usr/include/sys/cdefs.h:104:27: warning: garbage at end of #ifdef


The offending line is:
#  ifdef __STDC_VERSION__ && __STDC_VERSION__ >= 199901L

(??? should that be changed to
  # if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
}