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Sweep

Sweep is easy! Trace was probably the hardest part of the garbage collector.

Every object now has an is_marked field that we can use to determine if an object is reachable or not. All we need to do is iterate over all the objects in the VM and free any object that is not marked. Once it's freed, we can also remove it from our VM.

One more thing that's not obvious about sweep(): Any object that is marked (we don't want to free it right now) needs to be reset to is_marked = false. That way the next time the mark phase runs, if it's not marked again it will be freed in the next cycle.

Assignment

Complete the sweep function.
1. Iterate over all of the VM's objects:
  1. If the object is marked, reset is_marked = false and continue.
  2. Otherwise, free the object and set the data at that position in the stack to NULL.
2. Call stack_remove_nulls to remove any NULL objects from the VM's objects stack.
Complete the vm_collect_garbage function. This is it! This is the function that runs the GC.
1. Call mark.
2. Call trace.
3. Call sweep.

Hope you liked the course! Great work.

Hint

You can use the snek_object_free function to free the objects