This is the same problem on IRIX. You have to use the flex library like this: gcc ... -L(flex directory path) -lfl Gabor sorry to say but Gabor's advice didn't bring me any further. What I chose then was to set export LEXLIB="/opt/sfw/libfl.a" since this file holds yywrap. I made a make disclean ./configure make and everything went fine (at least there were no errors, warnings, notices or other complaints reported) and binaries were ceated. fyi we use: gcc 3.3 flex 2.5.4 libol 0.3.11 syslog-ng 1.6.0rc4 now the config will begin. kr