On amd64, gcc-4.0.1:
.....
GEN .version
CHK include/linux/compile.h
UPD include/linux/compile.h
CC init/version.o
LD init/built-in.o
LD .tmp_vmlinux1
net/built-in.o: In function `ip_ct_port_tuple_to_nfattr':
: undefined reference to `__nfa_fill'
net/built-in.o: In function `ip_ct_port_tuple_to_nfattr':
: undefined reference to `__nfa_fill'
net/built-in.o: In function `tcp_to_nfattr':
: undefined reference to `__nfa_fill'
net/built-in.o: In function `icmp_tuple_to_nfattr':
: undefined reference to `__nfa_fill'
net/built-in.o: In function `icmp_tuple_to_nfattr':
: undefined reference to `__nfa_fill'
net/built-in.o:: more undefined references to `__nfa_fill' follow
make: *** [.tmp_vmlinux1] Error 1