std::format/vasprintf

gistfile1.txt

int vasprintf(char** strp, const char* format, va_list ap)
{
    int len = _vscprintf(format, ap);
    if (len == -1)
        return -1;
    char* str = (char*)malloc((size_t)len + 1);
    if (!str)
        return -1;
    int retval = vsnprintf(str, len + 1, format, ap);
    if (retval == -1) {
        free(str);
        return -1;
    }
    *strp = str;
    return retval;
}

std::string format(const std::string fmt_str, ...)
{
    va_list ap;
    char* fp = NULL;
    va_start(ap, fmt_str);
    vasprintf(&fp, fmt_str.c_str(), ap);
    va_end(ap);
    std::unique_ptr<char[]> formatted(fp);
    return std::string(formatted.get());
}