Just dropped into `dev_mkdb: Segmentation fault' and found this:

    fs block size is 65536 (2^16). This is the default bucket size.

lib/libc/db/hash/hash_page.c contains:

    #define PAGE_INIT(P) { \
    	((u_int16_t *)(void *)(P))[0] = 0; \
    	((u_int16_t *)(void *)(P))[1] = hashp->BSIZE - 3 * sizeof(u_int16_t); \
    	((u_int16_t *)(void *)(P))[2] = hashp->BSIZE; \

which becomes:

	((u_int16_t *)(void *)(P))[0] = 0
	((u_int16_t *)(void *)(P))[1] = 65530;
	((u_int16_t *)(void *)(P))[2] = 65536; <== this becomes 0!!

P[1] is the amount of free space and P[2] is the free pointer.

What is the best solution to get rid of this bug?

Don't allow bucket size > 32768 (2^15)?
Set P[1] = 65529, P[2] = 65535  and discard the last byte of a page?
-- 
Juergen Hannken-Illjes - hannken@eis.cs.tu-bs.de - TU Braunschweig (Germany)