Dmitry reported this warning on FreeBSD since the introduction of -Wundef: admin/halog/fgets2.c:38:30: warning: '__GLIBC__' is not defined, evaluates to 0 [-Wundef] #if defined(__x86_64__) && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 15)) ^ A defined() was missing.