//----------------------------------------------------
// mgs.cc
//----------------------------------------------------

#include <iostream>  // std::cout
#include <sys/msg.h> // msgget, msgsnd, msgrcv, msgctl
#include <thread>    // std::thread

//----------------------------------------------------

using namespace std::literals;

//----------------------------------------------------

const size_t N = 8;

//----------------------------------------------------

class mgs_mutex
{
public:
    mgs_mutex(): id(msgget(IPC_PRIVATE, 0600)) { unlock(); }
    ~mgs_mutex() { msgctl(id, 0, IPC_RMID); }
    void lock() { msgrcv(id, &buffer, 0, 1, 0); }
    void unlock() { msgsnd(id, &buffer, 0, 0); }

private:
    struct msgbuf
    {
        long mtype;
        char mtext[1];
    };

    int id;
    msgbuf buffer = {1, {'\0'}};
} m;

//----------------------------------------------------

void seccion_critica()
{
    std::cout << "[" << std::this_thread::get_id() << "]: ";
    for (size_t i = 0; i < 10; ++i)
        std::cout << i;
    std::cout << std::endl;
}

//----------------------------------------------------

void hebra()
{
    while (true)
    {
        m.lock();
        seccion_critica();
        m.unlock();
    }
}

//----------------------------------------------------

int main()
{
    std::jthread threads[N];

    for (auto &i : threads)
        i = std::jthread(hebra);
}

//----------------------------------------------------