// note: we don't need a real printf format parser.
    //       enough to simply find the subtitution tokens and feed them to the real printf after checking types.
    //       https://en.wikipedia.org/wiki/Printf_format_string#Format_placeholder_specification
    FString output;
    bool in_fmt = false;
    FString fmt_current;
    int argnum = -1;
    int argauto = paramnum+1;
    // % = starts
    //  [0-9], -, +, \s, 0, #, . continue
    //  %, s, d, i, u, fF, eE, gG, xX, o, c, p, aA terminate
    // the only combination that is parsed locally is %n$...
    for (int i = 0; i < fmt.Len(); i++)
    {
        char c = fmt[i];
        if (in_fmt)
        {
            if ((c >= '0' && c <= '9') ||
                c == '-' || c == '+' || (c == ' ' && fmt_current[fmt_current.Len()-1] != ' ') || c == '#' || c == '.')
            {
                fmt_current += c;
            }
            else
            {
                if (argnum < 0) argnum = argauto;

                Printf("c = %c\n", c);

                switch (c)
                {
                case 's':
                {
                    PARAM_INT_AT(argnum, _s);
                    //PARAM_POINTER_AT(argnum, _s, int);
                    Printf("p = %s\n", FName(_s).GetChars());
                    //output += _s;
                    in_fmt = false;
                    break;
                }

                case 'd':
                case 'i':
                case 'u':
                case 'f':
                case 'F':
                case 'e':
                case 'E':
                case 'g':
                case 'G':
                case 'x':
                case 'X':
                case 'o':
                case 'c':
                case 'p':
                case 'a':
                case 'A':
                    output += "{arg}";
                    in_fmt = false;
                    break;
                default:
                    // invalid character
                    output += fmt_current + c;
                    in_fmt = false;
                    break;
                }
            }
        }
        else
        {
            if (c == '%')
            {
                if (i + 1 < fmt.Len() && fmt[i + 1] == '%')
                {
                    output += '%';
                    i++;
                }
                else
                {
                    in_fmt = true;
                    fmt_current = "%";
                    argnum = -1;
                }
            }
            else
            {
                output += c;
            }
        }
    }

    // list arguments for now
    /*paramnum++; // not sure if this is needed
    for (int i = 1; i < numparam; i++)
    {
        PARAM_STRING_AT()
    }*/