$ fgrep builtin_define /usr/src/contrib/gcc/config/freebsd-spec.h
builtin_define_with_int_value ("__FreeBSD__", FBSD_MAJOR); \
builtin_define_std ("unix"); \
builtin_define_std ("__unix__"); \
builtin_define ("__KPRINTF_ATTRIBUTE__"); \
builtin_define_with_int_value ("__FreeBSD_cc_version", FBSD_CC_VER); \