...xd5): undefined reference to `pthread_rwlock_wrlock' flock.o: In function `flock_rdlock': flock.c:(.text+0x135): undefined reference to `pthread_rwlock_rdlock' flock.o: In function `flock_unlock': flock.c:(.text+0x1d7): undefined reference to `pthread_rwlock_unlock' flock.o: In function `flock_destr...