O64
ATF_REQUIRE(O64(0x123456789abcdef0ull) == __bswap64(0x123456789abcdef0ull));
ATF_REQUIRE(O64(0x123456789abcdef0ull) == __bswap64(0x123456789abcdef0ull));
ATF_REQUIRE(O64(0x123456789abcdef0ull) == __bswap64(0x123456789abcdef0ull));
ATF_REQUIRE(O64(0x123456789abcdef0ull) == __bswap64(0x123456789abcdef0ull));