If I just run #./configure CC=gcc CFLAGS="-v #make It compiles fine. Looking at the log from make the include path is: . /usr/local/include /usr/local/lib/gcc/ia64-hp-hpux11.23/3.4.3/include /usr/include However, if I restrict the "Include" path to the following ./configure CC=gcc CFLAGS="-v -nostdinc -O2" CPPFLAGS="-I/usr/local/include -I/usr/local/lib/gc/ia64-hphpux11.23/3.4.3/include -I/usr/include" "make" spews out warnings like: /usr/local/lib/gcc/ia64-hp-hpux11.23/3.4.3/include/stdlib.h:30: warning: ignorin g #pragma builtin_milli abs /usr/local/lib/gcc/ia64-hp-hpux11.23/3.4.3/include/stdlib.h:31: warning: ignorin g #pragma extern abs /usr/local/lib/gcc/ia64-hp-hpux11.23/3.4.3/include/stdlib.h:65: warning: ignorin g #pragma builtin_milli div /usr/include/sys/signal.h:174: warning: ignoring #pragma extern signal /usr/include/sys/signal.h:191: warning: ignoring #pragma extern kill /usr/include/sys/signal.h:192: warning: ignoring #pragma extern sigismember /usr/include/sys/signal.h:193: warning: ignoring #pragma extern sigpending Thanks, Jenny-Lou