Possible. After all you are taking a list of a million, turning that into a list of about 6 million things, then allocating 6 million scalars. If each scalar takes 32 bytes, that is 192 MB just for the scalars, not even counting the space taken by the stack...

With 5.6.0 and earlier you would have had the same potential problem, but would likely get bored before taking enough hours to get there.