Concurrency is an essential aspect of modern software development, enabling programs to perform multiple tasks simultaneously. The C++ standard library provides several features and utilities to simplify concurrent programming. One such utility is std::jthread, introduced in C++20. In this blog post, we will explore how to use std::jthread for managing threads in C++.

Introduction to std::jthread

std::jthread is a new addition to the C++ standard library, providing a simplified interface for creating and managing threads. It is an improvement over the traditional approach of using std::thread, as it automatically joins or detaches the thread upon destruction, reducing the boilerplate code required.

Creating a std::jthread

Creating a std::jthread is straightforward. We can pass a callable object or a function pointer to the constructor, and the thread will start executing immediately. Let’s see an example:

#include <iostream>
#include <thread>

void myFunction()
{
    std::cout << "Thread executing" << std::endl;
}

int main()
{
    std::jthread myThread(myFunction);
    
    // Rest of the main thread code
    
    return 0;
}

In the above example, we define a function myFunction that will be executed by the thread. We then create a std::jthread object myThread, passing myFunction as the callable. The thread starts immediately, and the main thread continues its execution.

Detaching a std::jthread

Sometimes, we may want a thread to run independently without joining it. In such cases, we can detach the thread using the detach() member function. Here’s an example:

#include <iostream>
#include <thread>

void myFunction()
{
    std::cout << "Detached thread executing" << std::endl;
}

int main()
{
    std::jthread myThread(myFunction);
    
    myThread.detach();
    
    // Rest of the main thread code
    
    return 0;
}

In the above example, after creating the std::jthread object myThread, we call the detach() function to detach the thread. Once detached, the thread will continue executing independently, and we no longer need to join it.

Joining a std::jthread

When we want the main thread to wait for a std::jthread to complete its execution, we can use the join() member function. Here’s an example:

#include <iostream>
#include <thread>

void myFunction()
{
    std::cout << "Thread executing" << std::endl;
}

int main()
{
    std::jthread myThread(myFunction);
    
    myThread.join();
    
    // Rest of the main thread code
    
    return 0;
}

In the above example, the main thread calls the join() function on the std::jthread object myThread, which blocks until the thread has finished its execution. Once joined, the main thread can continue with the remaining code.

Summary

The std::jthread utility simplifies thread management in C++, providing automatic join or detach functionality. By leveraging std::jthread, we can write cleaner and more concise concurrent code. With its ease of use, std::jthread is a valuable addition for anyone working with concurrent programming in C++.

#concurrency #C++