c++ typeless format

#include <string>
#include <sstream>

void format(std::ostringstream& ss, const char* fmt)
{
    if (!fmt || *fmt == '\0')
    {
        return;
    }
    while (*fmt != '\0')
    {
        if (*fmt == '%')
        {
            ++fmt;
            if (*fmt == '?')
            {
                ++fmt;
                ss << '?';
                break;
            }
            else if (*fmt != '%')
                continue;
        }
        ss << *fmt;
        ++fmt;
    }
}

template <typename H, typename... T>
void format(std::ostringstream& ss, const char* fmt, H&& p, T&&... t)
{
    if (!fmt || *fmt == '\0')
    {
        return;
    }
    while (*fmt != '\0')
    {
        if (*fmt == '%')
        {
            ++fmt;
            if (*fmt == '?')
            {
                ++fmt;
                ss << std::forward<H>(p);
                break;
            }
            else if (*fmt != '%')
                continue;
        }
        ss << *fmt;
        ++fmt;
    }
    format(ss, fmt, std::forward<T>(t)...);
}

template <typename... T>
std::string format(const char* fmt, T... t)
{
    std::ostringstream oss;
    format(oss, fmt, std::forward<T>(t)...);
    return oss.str();
}

#include <iostream> // for std::cout

int main()
{
    {
        unsigned long long u = -1;
        long long i = -1;
        char c = 100;
        std::cout << format("asd %? %? %? % %%", i, u, c) << std::endl;
        return 0;
    }
}