terminate called after throwing an instance of 

Question

When I run my code :

nb workers = 12
I'm i : 0
HELLO I'm func1
BYE I'm func2
terminate called after throwing an instance of 'std::system_error'
  what():  Invalid argument
Aborted (core dumped)

terminate called after throwing an instance of 'std::system_error'l

what(): Invalid argument

#ifndef CPP_PLAZZA_EXAMPLE_H
#define CPP_PLAZZA_EXAMPLE_H

#include <thread>
#include <vector>
#include <list>
#include <memory>
#include <functional>
#include <mutex>
#include <condition_variable>
#include <atomic>
#include <iterator>
#include <tuple>

class ThreadPool
{
 public:
  ThreadPool(size_t numThreads);
  virtual ~ThreadPool();
  void executeJob(std::function<void()> job, std::function<void()> notificationJob);
  void wait_for_done();
 private:
  void loop();
  std::pair<std::function<void()>, std::function<void()> > getNextJob();
  std::vector<std::thread> m_workers;
  std::list<std::pair<std::function<void()>, std::function<void()> > > m_jobs;
  std::mutex m_lockJobsList;
  std::condition_variable m_notifyJob;
  std::atomic<bool> m_bTerminate;
  class Terminated: public std::runtime_error
  {
   public:
    Terminated(const std::string& what): std::runtime_error(what) {}
  };

};

#endif //CPP_PLAZZA_EXAMPLE_H

and here it is my .cpp

#include <iostream>
#include "example.h"


ThreadPool::ThreadPool(size_t numThreads):
 m_workers(numThreads), m_bTerminate(false) {
  m_workers.reserve(numThreads);
  for (size_t i = 0; i < numThreads; i++) {
    this->m_workers.emplace_back(&ThreadPool::loop, this);
  }
  /*for (std::vector<std::thread>::iterator it = this->m_workers.begin(); it != this->m_workers.end(); it++)
    assert(std::next(it, 1) ==);*/
}

ThreadPool::~ThreadPool() {
    {
        std::unique_lock<std::mutex> lockList(m_lockJobsList);
        m_bTerminate = true;
        m_notifyJob.notify_all();
    }

/*  for(std::vector<std::thread>::iterator it = m_workers.begin(); it != m_workers.end(); it++) {
    it->join();
  }*/
  std::this_thread::sleep_for(std::chrono::seconds(5));
}

void ThreadPool::executeJob(std::function<void()> job, std::function<void()> notificationJob) {
    std::unique_lock<std::mutex> lockList(m_lockJobsList);
  m_jobs.emplace_back(std::pair<std::function<void()>, std::function<void()> >(std::move(job), std::move(notificationJob)));
  std::cout << m_jobs.size() << std::endl;
    m_notifyJob.notify_one();
}

std::pair<std::function<void()>, std::function<void()> > ThreadPool::getNextJob() {
    std::unique_lock<std::mutex> lockList(m_lockJobsList);

    while(!m_bTerminate)
    {
        if(!m_jobs.empty())
        {
            std::pair<std::function<void()>, std::function<void()>> job = std::ref(m_jobs.front());
            m_jobs.pop_front();
            return job;
        }

        m_notifyJob.wait(lockList);
    }

    throw Terminated("Thread terminated");
}

void        func1() {
  std::cout << "HELLO I'm func1" << std::endl;

}

void ThreadPool::loop()
{
    try
    {
        for(;;)
        {
      std::pair<std::function<void()>, std::function<void()> > job = getNextJob();
      job.first();
      job.second();
        }
    }
    catch(Terminated& e)
    {
    }
}



void        func2() {
  std::cout << "BYE I'm func2" << std::endl;

}

void        ThreadPool::wait_for_done()
{
  std::cout << "nb workers = " << this->m_workers.size() << std::endl;
  int i = 0;
  for(std::vector<std::thread>::iterator it = m_workers.begin(); it != m_workers.end(); ++it) {
    std::cout << "je suis i :  " << i << std::endl;
    i++;

    (*it).join();
  }
}

int     main()
{
  ThreadPool        pool(6);

  pool.executeJob(func1, func2);
  pool.wait_for_done();
}

I think that my error is I join several time on one thread but how to fix it ?

Compilation line :

g++ -Wall -Werror -W -Wextra example.cpp -pthread -std=c++11

I tried joinable before join like this (in wait for done) :

for(std::vector<std::thread>::iterator it = m_workers.begin(); it != m_workers.end(); ++it) {
    if ((*it).joinable())
        (*it).join();
  }

And I had an infinite loop

Answer 1

Your m_lockJobsList mutex (and m_notifyJob condvar) gets destroyed before m_workers threads that try to lock it when wake after condvar notification at ThreadPool destructor.