Can't build FreeBSD-head with CLANG

I can't build FreeBSD (GENERIC & custom kernel) with clang. Build
finishes for i386 and fails for amd64 for same kernels

I have bsd box with following clang version:
> FreeBSD clang version 3.0 (branches/release_30 142614) 20111021
> Target: x86_64-unknown-freebsd10.0
> Thread model: posix

I try to compile it with /dev/null as make.conf and following src.conf:
> WITHOUT_AMD="YES"
> WITHOUT_ASSERT_DEBUG="YES"
> WITHOUT_ATM="YES"
> WITH_BIND_LARGE_FILE="YES"
> WITH_BIND_SIGCHASE="YES"
> WITH_BSD_GREP="YES"
> WITHOUT_CTM="YES"
> WITH_CLANG="YES"
> WITH_CLANG_EXTRAS="YES"
> WITH_CLANG_IS_CC="YES"
> WITH_CTF="YES"
> WITHOUT_DYNAMICROOT="YES"
> WITHOUT_FLOPPY="YES"
> WITH_ICONV="YES"
> WITHOUT_IPFILTER="YES"
> WITHOUT_IPFW="YES"
> WITHOUT_IPX="YES"
> WITHOUT_IPX_SUPPORT="YES"
> WITHOUT_NCP="YES"
> WITHOUT_NIS="YES"
> WITHOUT_NLS_CATALOGS="YES"
> WITHOUT_TCSH="YES"
> WITHOUT_RCMDS="YES"

but I constantly get warnings (not long ago they was errors) in kernel
like this:
/usr/head/src/sys/netgraph/ng_parse.c:1263:14: warning: comparison of
unsigned expression < 0 is always false [-Wtautological-compare]
                        if (index < 0 || eptr - (s + *off) != len) {
                            ~~~~~ ^ ~
1 warning generated.

Also I get not initialized warnings and so on.

I don't want build it with gcc.

-- Eir Nym