WickedEngine | 3D engine with modern graphics | Game Engine library

First, your pool creates 4 working threads. Then, in main, you add some tasks into the pool queue, which call dss.DoSomething();.

The workers then start executing these tasks. Inside, they first enqueue some more tasks, and then, they start waiting for their futures forever. These waits never end since there are no threads that could start resolving the next enqueued tasks.

Creating a thread pool with the ability to enqueue tasks from within processed tasks is not trivial. Basically, what you would need is to suspend the current task here instead of waiting. There is no native mechanism for this in C++ (at least, until C++20 coroutines).

As a workaround, you can use OpenMP or Intel TBB, which both provide the described functionality. For example, in OpenMP, you can suspend a current task and wait for its sub-tasks completion with #pragma omp takswait.