When booted into the loader(8) interactive prompt (ok>), character addresses (c-addr) are showing up negative when using ".s" to display the stack contents.
Press ESC at the boot loader menu to enter the loader(8) interactive prompt. Type the following at the "ok>" prompt:
s" hello, world!" .s
and then press ENTER. You'll notice that the first number is negative. Previous FreeBSD builds did not have this issue and it is confusing to see a negative number on the stack despite being a perfectly valid character address.