Handling Exceptions in Multithreaded C++ Programs

Handling exceptions in a multithreaded C++ program can be challenging because exceptions thrown in one thread do not propagate to other threads.

Each thread operates independently, so exception handling must be managed within the thread itself. Here’s how you can handle exceptions in a multithreaded environment:

1. Catch exceptions within each thread: Ensure that each thread catches exceptions to avoid unhandled exceptions that could terminate the thread or the entire program.
2. Communicate exceptions to the main thread: Use mechanisms such as std::promise and std::future to pass exceptions from worker threads to the main thread.

Here’s an example to illustrate this:

1#include <future>
2#include <iostream>
3#include <stdexcept>
4#include <thread>
5
6void Task(std::promise<void>&& promise) {
7  try {
8    // Simulate an error
9    throw std::runtime_error("Something went wrong!");
10  } catch (...) {
11    promise.set_exception(std::current_exception());
12  }
13}
14
15int main() {
16  std::promise<void> promise;
17  std::future<void> future = promise.get_future();
18  std::thread t(Task, std::move(promise));
19
20  try {
21    future.get();
22  } catch (const std::exception& e) {
23    std::cout << "Exception caught: " << e.what();
24  }
25
26  t.join();
27}

1Exception caught: Something went wrong!

In this example, the Task function throws an exception, which is caught and set on the std::promise. The main thread retrieves this exception through the std::future and handles it.

Key points to remember:

• Always catch exceptions within each thread to prevent unexpected termination.
• Use std::promise and std::future for safe exception communication between threads.
• Consider using a thread pool to manage multiple threads and handle exceptions more effectively.

This approach ensures that exceptions in worker threads are properly handled and can be communicated back to the main thread or a central exception handler.