cipher/rndunix.c needs to include sys/types.h and signal.h. ./rndunix.c: In function `my_popen': ./rndunix.c:431: warning: implicit declaration of function `kill' ./rndunix.c: In function `start_gatherer': ./rndunix.c:699: warning: implicit declaration of function `signal' This is on Solaris, but I believe all systems are affected.