WARNS higher than 3 produces a number of "cast ... increases required alignment", with one example below. Will revisit that later on.

WARNS higher than 3 produces:

/usr/home/emaste/src/freebsd/usr.sbin/makefs/ffs.c:993:8: error: cast from
      'u_char *' (aka 'unsigned char *') to 'struct direct *' increases required
      alignment from 1 to 4 [-Werror,-Wcast-align]
                de = (struct direct *)(dbuf->buf + i);
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I suspect that you need to cast through uintptr_t. Like

de = (struct direct *)(uintptr_t)(buf + 1);

Note that in-kernel ffs_hashalloc() uses the following prototype:

static ufs2_daddr_t	ffs_hashalloc
		(struct inode *, u_int, ufs2_daddr_t, int, int, allocfcn_t *);

Kernel uses u_int for cg and startcg.

Yes, as long as we know that it must have the correct alignment (which is probably straightforward to demonstrate, but I haven't yet looked).

I wonder though if the warning is just overly aggressive, and if we should just disable it.

Ok. I think I based this on fs_ncg being u_int32_t, but if kernel uses u_int it probably makes sense to follow here.