USE_EPOLL : enable epoll() on Linux 2.6. Automatic. USE_KQUEUE : enable kqueue() on BSD. Automatic. USE_EVPORTS : enable event ports on SunOS systems. Automatic. USE_NETFILTER : enable netfilter on Linux. Automatic. USE_PCRE : enable use of libpcre for regex. Recommended. USE_PCRE_JIT : enable JIT for faster regex on libpcre >= 8.32 USE_PCRE2 : enable use of libpcre2 for regex. USE_PCRE2_JIT : enable JIT for faster regex on libpcre2 USE_POLL : enable poll(). Automatic. USE_THREAD : enable threads support. USE_STATIC_PCRE : enable static libpcre. Recommended. USE_STATIC_PCRE2 : enable static libpcre2. USE_TPROXY : enable transparent proxy. Automatic. USE_LINUX_TPROXY : enable full transparent proxy. Automatic. USE_LINUX_SPLICE : enable kernel 2.6 splicing. Automatic. USE_LINUX_CAP : enable Linux capabilities. USE_LIBCRYPT : enable encrypted passwords using -lcrypt USE_CRYPT_H : set it if your system requires including crypt.h USE_GETADDRINFO : use getaddrinfo() to resolve IPv6 host names. USE_OPENSSL : enable use of OpenSSL. Recommended, but see below. USE_OPENSSL_WOLFSSL : enable use of wolfSSL with the OpenSSL API USE_QUIC : enable use of QUIC with the quictls API (quictls, libressl, boringssl) USE_ENGINE : enable use of OpenSSL Engine. USE_LUA : enable Lua support. USE_ACCEPT4 : enable use of accept4() on linux. Automatic. USE_CLOSEFROM : enable use of closefrom() on *bsd, solaris. Automatic. USE_PRCTL : enable use of prctl(). Automatic. USE_PROCCTL : enable use of procctl(). Automatic. USE_ZLIB : enable zlib library support and disable SLZ USE_SLZ : enable slz library instead of zlib (default=enabled) USE_CPU_AFFINITY : enable pinning processes to CPU on Linux. Automatic. USE_TFO : enable TCP fast open. Supported on Linux >= 3.7. USE_NS : enable network namespace support. Supported on Linux >= 2.6.24. USE_DL : enable it if your system requires -ldl. Automatic on Linux. USE_MATH : enable use of -lm. Automatic. USE_RT : enable it if your system requires -lrt. Automatic on Linux. USE_BACKTRACE : enable backtrace(). Automatic on Linux. USE_PROMEX : enable the Prometheus exporter USE_DEVICEATLAS : enable DeviceAtlas api. USE_51DEGREES : enable third party device detection library from 51Degrees USE_WURFL : enable WURFL detection library from Scientiamobile USE_SYSTEMD : enable sd_notify() support. USE_OBSOLETE_LINKER : use when the linker fails to emit __start_init/__stop_init USE_THREAD_DUMP : use the more advanced thread state dump system. Automatic. USE_OT : enable the OpenTracing filter USE_MEMORY_PROFILING : enable the memory profiler. Linux-glibc only. USE_LIBATOMIC : force to link with/without libatomic. Automatic. USE_PTHREAD_EMULATION: replace pthread’s rwlocks with ours USE_SHM_OPEN : use shm_open() for the startup-logs