Ingo Molnar writes:

ah, it does this:

/*
 * This is here because we used to use l64 for 64bit powerpc
 * and we don't want to impact user mode with our change to ll64
 * in the kernel.
 */
#if defined(__powerpc64__) && !defined(__KERNEL__)
# include <asm-generic/int-l64.h>
#else
# include <asm-generic/int-ll64.h>
#endif

That's crappy really.

We were concerned that changing the userland-visible type of __u64
from unsigned long to unsigned long long, etc., would be breaking the
ABI, even if only in a small way - I thought it could possibly change
C++ mangled function names, for instance, and it would cause fresh
compile warnings on existing user code that prints __u64 with %lx,
which has always been the correct thing to do on ppc64.

A counter-argument would be, I guess, that __u64 et al. are purely for
use in describing the kernel/user interface, so we have a little more
latitude than with the type of e.g. u_int64_t.  I dunno.  I don't
recall getting much of an answer from the glibc guys about what they
thought of the idea of changing it.

Anyway, of the 64-bit architectures, alpha, ia64, and mips64 also have
__u64 as unsigned long in userspace, so this issue will still crop up
even if we change it on powerpc.

Paul.