Capturing Exceptions in a Different Thread

One way to capture an exception in one thread and handle it in another is to use std::exception_ptr in combination with std::current_exception() and std::rethrow_exception():

1#include <exception>
2#include <iostream>
3#include <thread>
4
5std::exception_ptr captureException() {
6  try {
7    throw std::runtime_error("Error in thread");
8  } catch(...) {
9    return std::current_exception();
10  }
11}
12
13void handleException(std::exception_ptr eptr) {
14  try {
15    if (eptr) {
16      std::rethrow_exception(eptr);
17    }
18  } catch(const std::exception& e) {
19    std::cout << "Caught exception: "
20      << e.what() << "\n";
21  }
22}
23
24int main() {
25  std::exception_ptr eptr;
26  std::thread t([&]{
27    eptr = captureException();
28  });
29  t.join();
30  handleException(eptr);
31}

1Caught exception: Error in thread

The key steps are:

1. In the thread where the exception occurs, catch the exception and capture it into a std::exception_ptr using std::current_exception().
2. Transfer this std::exception_ptr to the thread where you want to handle the exception.
3. In the handling thread, use std::rethrow_exception() to rethrow the original exception, which can then be caught and handled as usual.

This allows exceptions to cross thread boundaries while preserving their type information.