cpp condition_variable wait_until unique_mutex time_out

#include <chrono>
#include <condition_variable>
#include <ctime>
#include <fstream>
#include <future>
#include <iomanip>
#include <iostream>
#include <map>
#include <mutex>
#include <sstream>
#include <thread>
#include <uuid/uuid.h>
#include <vector>

std::string get_time_now()
{
    std::chrono::time_point<std::chrono::high_resolution_clock> now = std::chrono::high_resolution_clock::now();
    time_t raw_time = std::chrono::high_resolution_clock::to_time_t(now);
    struct tm tm_info = *localtime(&raw_time);
    std::stringstream ss;
    std::chrono::seconds seconds = std::chrono::duration_cast<std::chrono::seconds>(now.time_since_epoch());
    std::chrono::milliseconds mills = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch());
    std::chrono::microseconds micros = std::chrono::duration_cast<std::chrono::microseconds>(now.time_since_epoch());
    std::chrono::nanoseconds nanos = std::chrono::duration_cast<std::chrono::nanoseconds>(now.time_since_epoch());
    ss << std::put_time(&tm_info, "%Y%m%d%H%M%S") 
       << std::setw(3) << std::setfill('0') << std::to_string(mills.count() - seconds.count() * 1000)
       << std::setw(3) << std::setfill('0') << std::to_string(micros.count() - mills.count() * 1000)
       << std::setw(3) << std::setfill('0') << std::to_string(nanos.count() - micros.count() * 1000);
    return ss.str();
} 

char *uuid_value = (char *)malloc(40);
char *get_uuid()
{
    uuid_t new_uuid;
    uuid_generate(new_uuid);
    uuid_unparse(new_uuid, uuid_value);
    return uuid_value;
}
 
std::condition_variable cv;
std::mutex _mtx;
bool is_done = false;
void condition_variable_wait_for_seconds(const int &wait_seconds)
{    
    std::chrono::time_point<std::chrono::high_resolution_clock> time_out = std::chrono::high_resolution_clock::now() + std::chrono::seconds(wait_seconds);
    std::unique_lock<std::mutex> lk(_mtx);
    while (1)
    {
        if (cv.wait_until(lk, time_out) == std::cv_status::timeout)
        {
            is_done = true;
            break;
        }
    } 
}

void log_file_time()
{     
    std::fstream w_file("log.txt", std::ios::app);
    if (!w_file.is_open())
    {
        std::cout << "Create or open log.txt failed!" << std::endl;
        return;
    }
    std::stringstream ss;
    std::uint64_t num = 0;
    while (!is_done)
    {
        ss << ++num << "," << get_uuid() << std::endl;
        if (num % 1000000 == 0)
        {
            w_file << ss.str();
            ss = std::stringstream();
            std::cout << num << "," << get_time_now() << "," << get_time_now() << std::endl;
        }
        if (is_done)
        {
            w_file << ss.str();
            ss = std::stringstream();
            std::cout << std::boolalpha << num << "," << get_time_now() << "," << get_time_now()<< ",is_done:" << is_done << std::endl;
            break;
        }
    } 
}

void mt_condition_variable(const int &wait_seconds)
{
    std::stringstream ss;
    ss << get_time_now() << ",start in " << __FUNCTION__ << std::endl;
    std::thread t1(condition_variable_wait_for_seconds, std::cref(wait_seconds));
    std::thread t2(log_file_time);
    t1.join();
    t2.join();
    ss << get_time_now() << ",finish in " << __FUNCTION__ << std::endl;
    std::cout << ss.str();
}

int main(int args, char **argv)
{
    mt_condition_variable(atoi(argv[1]));
}

g++ -g -std=c++2a -I. *.cpp -o h1 -luuid -lpthread

./h1 1000