proper types for printf()-ing pointers on amd64 that won't break
Lowell Gilbert
freebsd-bugs at be-well.ilk.org
Thu Sep 18 18:45:45 UTC 2008
"Steve Franks" <stevefranks at ieee.org> writes:
> Hi,
>
> I'm trying to correct some warnings in a port marked
> ONLY_FOR_ARCHS=i386. They stem from casting a pointer (which I assume
> is a 64-bit unsigned) to "unsigned int" which is apparently 32 bits?
> I sort of thought int was supposed to be the atomic register size, but
> no doubt that would break more than it would help, so it's 32-bits.
> Anyways, what's the right way to fix this? The port actually works
> fine as-is on amd64, so I can only assume something was fixed for 7.1,
> or someone was being extra cautious with the i386 tag.
>
> The code:
>
> typedef unsigned int cardinal;
> ...
> fprintf(stderr, "Mode Table Offset: $C0000 + $%x\n",
> ((cardinal)map->mode_table) - ((cardinal)map->bios_ptr));
>
> Can I just ditch the cast+%x and use %p? I don't have an i386 system
> to test on, and I don't want to break anything if I submit a patch...
What is actually being printed isn't a pointer, but the difference
between two pointers (I assume from your comments; the code included
isn't enough to show where they come from). That means the correct
type of what's being printed is size_t, which our printf seems to
support with a "z" modifier. Removing the explicit casts or (if
necessary), replacing them with something that is big enough will also
be needed.
More information about the freebsd-hackers
mailing list