POSIX requires <stdio.h> and <unistd.h> to define off_t and ssize_t like <sys/types.h> does, but not all platforms respect that. Play it safe by always including <sys/types.h>.
Instead of having libcryb-test provide main() and assume that the test program defines t_prepare() and t_cleanup(), have libcryb-test provide a t_main() function which the test program calls with pointers to its prepare and cleanup functions.
anywhere. Opinion is divided as to whether this is useful, or whether
its usefulness is outweighed by its awkwardness. Still, we have it, so
we may as well commit it.