> With RAII popping stack frames means freeing resources recursively. If your free() implementation takes a lock then that can block other threads too, for an a

> With RAII popping stack frames means freeing resources recursively. If your free() implementation takes a lock then that can block other threads too, for an arbitrary time if the object graph being released is large. For every RAII implementation I've seen, the recursive part is not within the free() implementation; the recursion happens outside the free() (or equivalent) calls, and free() (or equivalent) is called separately for each step, to release the memory for just that step. The time taken by each free() call is independent from the size of the object graph being released.