1. Introduction

Brief Explanation of the Tutorial's Goal

In this tutorial, we will dive deep into the concepts of synchronization and thread safety in C++. Synchronization is a key concept in multi-threaded programming that prevents threads from accessing any shared resource concurrently. Understanding synchronization and thread safety is fundamental to writing robust multi-threaded code.

What the User Will Learn

• The basics of synchronization and thread safety
• Different synchronization primitives
• How to write thread-safe code
• Best practices for synchronization and thread safety

Prerequisites

Familiarity with C++ programming is necessary. Basic knowledge of multi-threading would be beneficial but is not mandatory.

2. Step-by-Step Guide

Synchronization

Synchronization is a mechanism that ensures that two or more concurrent threads do not simultaneously execute some particular program segment known as a critical section.

Why Do We Need Synchronization?

In a multi-threaded environment, multiple threads can access shared resources. Without proper synchronization, if these threads manipulate a shared resource concurrently, the final value of the resource can be unpredictable, leading to bugs that are hard to detect and correct.

Thread Safety

Thread safety means that the shared data manipulated by threads is done so in a manner that guarantees safe execution by multiple threads at any given time.

Synchronization Primitives

The C++ Standard Library provides several synchronization primitives, including mutex, recursive_mutex, timed_mutex, recursive_timed_mutex, lock_guard, unique_lock, shared_mutex, shared_lock, condition variable, etc.

Best Practices

• Always lock your shared resources when you access them
• Minimize the scope of locks
• Avoid deadlock situations

3. Code Examples

Mutex in C++

#include <iostream>
#include <thread>
#include <mutex>

std::mutex mtx;

void print_block (int n, char c) {
  mtx.lock();
  for (int i=0; i<n; ++i) { std::cout << c; }
  std::cout << '\n';
  mtx.unlock();
}

int main () {
  std::thread th1 (print_block,50,'*');
  std::thread th2 (print_block,50,'$');

  th1.join();
  th2.join();

  return 0;
}

In this example, we use a mutex to synchronize threads. The mutex is locked before accessing the shared resource (std::cout) and then unlocked after the resource is no longer needed.

4. Summary

In this tutorial, we have covered the basics of synchronization and thread safety in C++. We also discussed different synchronization primitives provided by the C++ standard library, and we went through a simple example of mutex usage for synchronization.

5. Practice Exercises

1. Exercise: Write a C++ program where two threads increment a shared integer variable without using any synchronization primitives. Observe if the final value of the variable is as expected.

2. Exercise: Modify the above program to use a mutex for synchronization. Observe if the final value of the variable is now as expected.

Tips for further practice: Try out different synchronization primitives and also try to create more complex scenarios where multiple threads access multiple shared resources. Always remember to avoid deadlocks and minimize the scope of locks.