... pcntl.o -lxapian flock.o: In function `flock_set_thread_safe': flock.c:(.text+0xa7): undefined reference to `pthread_rwlock_init' flock.o: In function `flock_wrlock': flock.c:(.text+0xd5): undefined reference to `pthread_rwlock_wrlock' flock.o: In function `flock_rdlock': flock.c:(.text+0x135): un...