--gc:arc. Plain reference counting with move semantic optimizations, offers a shared heap. It offers deterministic performance for hard realtime systems. Reference cycles cause memory leaks, beware. --gc:orc. Same as -gc:arc but adds a cycle collector based on "trial deletion". Unfortunately that makes its performance profile hard to reason about so it is less useful for hard realtime systems. --gc:none. No memory management strategy nor garbage collector. Allocated memory is simply never freed. You should use --gc:arc instead.

Nim offers alloc, dealloc, allocShared, deallocShared