root@pflog:/usr/src# grep -rHsi '__h_errno' .
./contrib/bind9/lib/bind/resolv/herror.c:       DE_CONST(hstrerror(*__h_errno()), t);
./contrib/bind9/lib/bind/irs/irs_data.c:__h_errno(void) {
./contrib/bind9/lib/bind/irs/irs_data.c:__h_errno_set(struct __res_state *res, int err) {
./contrib/bind9/lib/bind/include/resolv.h: *    (and __h_errno_set) to the public via <resolv.h>.
./contrib/bind9/lib/bind/include/resolv.h: * XXX:       __h_errno_set is really part of IRS, not part of the resolver.
./contrib/bind9/lib/bind/include/resolv.h: *            # define RES_SET_H_ERRNO(r,x) __h_errno_set(r,x)
./contrib/bind9/lib/bind/include/resolv.h:#define RES_SET_H_ERRNO(r,x) __h_errno_set(r,x)
./contrib/bind9/lib/bind/include/resolv.h:void __h_errno_set(struct __res_state *res, int err);
./contrib/bind9/lib/bind/include/netdb.h:#define __h_errno __h_errno_location
./contrib/bind9/lib/bind/include/netdb.h:extern int * __h_errno __P((void));
./contrib/bind9/lib/bind/include/netdb.h:#define        h_errno (*__h_errno())