*`sem_freelist` tracks the number of blocks on the `freelist`.
* This prevents any thread from trying to read a nonexistent (`nullptr`) block from the `freelist`.
*`sem_freelist_minus_1` tracks the number of blocks on the `freelist` minus 1:
* This is used to circumvent a deadlock situation where Thread-1 (the producer) will eat the last block on the `freelist` and put it on `list1`, where Thread-2 (the transformer) will never be able to consume it, since it's blocked on the empty `freelist`.
* Without this, you'd need to check that `sem_freelist > 1`, and the project specifications only allow the use of P() and V(), A.K.A. `wait()` and `signal()`.
*`sem_list1` tracks the number of blocks on `list1`.
* This prevents any thread from trying to read a nonexistent (`nullptr`) block from `list1`.
*`sem_list2` tracks the number of blocks on `list2`.
* This prevents any thread from trying to read a nonexistent (`nullptr`) block from `list2`.
All counting semaphores were used for thread synchronization.
### Binary Semaphores:
This project uses three binary semaphores:
*`sem_freelist` guarantees mutual exclusion when accessing the `freelist`.
* This prevents memory corruption, as list accesses are thread-unsafe.
*`sem_list1` guarantees mutual exclusion when accessing `list1`.
* This prevents memory corruption, as list accesses are thread-unsafe.
*`sem_list2` guarantees mutual exclusion when accessing `list2`.
* This prevents memory corruption, as list accesses are thread-unsafe.
All binary semaphores were used for mutual exclusion.
