> If I remember correctly the problem is that some OS like linux (and
probably others) do not really allocate space until something is written.
If that's the case then the process may get killed later on when it writes
something in the array.

Yes, it's called overcommitting, and it's a good thing. It's exactly the
same thing for memory: malloc() can return non-NULL, and the process will
get killed when first writing to the page in case of memory pressure.