Logging with a custom terminate handler

You can use a custom terminate handler to log information about an unhandled exception before terminating the program. Here's an example of how you can set up a custom terminate handler for logging:

1#include <exception>
2#include <iostream>
3
4void customTerminateHandler() {
5  try {
6    std::exception_ptr exPtr =
7      std::current_exception();
8    if (exPtr) {
9      std::rethrow_exception(exPtr);
10    }
11  } catch (const std::exception& ex) {
12    std::cout << "Unhandled exception: "
13      << ex.what() << '\n';  
14  } catch (...) {
15    std::cout << "Unhandled unknown exception\n";
16  }
17  std::abort();
18}
19
20int main() {
21  std::set_terminate(customTerminateHandler);
22
23  try {
24    throw std::runtime_error(
25      "Something went wrong");
26  } catch (const std::logic_error& ex) {
27    // Catch and handle logic_error exceptions
28  }
29}

1Unhandled exception: Something went wrong

In this example:

1. We define a custom terminate handler function customTerminateHandler.
2. Inside the handler, we retrieve the currently thrown exception using std::current_exception().
3. If an exception pointer is obtained, we rethrow the exception to catch and log its details.
4. We catch specific exception types (e.g., std::exception) and log their error messages using ex.what().
5. For unknown exceptions, we log a generic message.
6. Finally, we call std::abort() to terminate the program.

In the main() function:

1. We set the custom terminate handler using std::set_terminate().
2. We intentionally throw an exception that is not caught by the provided catch block.

When the unhandled exception is thrown, the custom terminate handler is invoked, logging the exception details before terminating the program.