Handling exceptions from detached threads

[ptsouchlos]

From: @JuniorSuperTux

Any thoughts on implementing API for getting exceptions from the detached threads?

[ptsouchlos]

First, I assume that by a detached thread, you mean like when you call thread.detach() right?

If so, my question would be why you're interested in the exception state of a detached thread. Could you explain a bit about your use case?

[JuniorSuperTux]

I'm not sure if I learnt correctly, but there's boost::io_context in boost which allows callbacks to be run in an asynchronous manner, and what I guess I'll do is iterate through all the io_context and pass all the objects and io_context::run function pointer directly to the thread pool without ever calling get. And from what I've read io_context::run throws exceptions, and I would like to check them.

(I'm totally unsure whether I'm talking some nonsense bullshit rn)

[ptsouchlos]

I see. So, in the context of my thread pool library, you would do this through the std::future interface. When the thread pool executes the work, it captures exceptions (if any) and passes them to the std::promise and thus back to the caller through the returned std::future object.

So you could do:

// assume the task throws an exception
auto throw_future = pool.enqueue(throw_task, 1);
// the exception is caught and put into the future. 
// getting the future will re-throw the exception
auto result = throw_future.get();

Hopefully that makes sense and is what you're looking for.