float to string using x87 BCD

#include <iostream>
#include <iomanip>

#include <cstdint>
#include <cstdlib>

int
main()
{

    auto const x = -10000000000000000.0L;
    union
    {
        std::uint8_t in[10];
        struct
        {
            std::uint64_t out8;
            std::uint8_t out1;
            unsigned : 7;
            unsigned sign : 1;
        };
    };
    asm("fld %1\n" "fbstp %0" : "=m"(in) : "f"(x) : "memory");
    std::cout << std::hex << std::noshowbase;
    if (sign != 0) {
        std::cout << '-';
    }
    if (out1 != 0) {
        std::cout << std::uint16_t(out1) << std::setfill('0') << std::setw(16);
    }
    std::cout << out8 << std::endl;
    return EXIT_SUCCESS;
}