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Modern C++ Concurrency: Get the most out of any machine

Arguments of Threads: Undefined behavior

Understand the causes of undefined behavior when thread arguments are improperly handled in C++. This lesson examines thread argument passing by reference and its effects on concurrency, preparing you to identify and resolve common issues in multithreaded programs.

We'll cover the following...

As discussed in the previous lesson, here is another example of undefined behavior caused by improper handling of thread arguments.

C++
// threadArguments.cpp
#include <chrono>
#include <iostream>
#include <thread>
class Sleeper{
  public:
    Sleeper(int& i_):i{i_}{};
    void operator() (int k){
      for (unsigned int j= 0; j <= 5; ++j){
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
        i += k;
      }
      std::cout << std::this_thread::get_id() << std::endl;
    }
  private:
    int& i;
};
int main(){
  std::cout << std::endl;
  int valSleeper = 1000;
  std::thread t(Sleeper(valSleeper), 5);
  t.detach();
  std::cout << "valSleeper = " << valSleeper << std::endl;
  std::cout << std::endl;
}

The question is, what value does valSleeper have in line 29? ...