The functions system_info and system_flag are BIF's which make calls to the c code found in the file erl_bif_info.c , this code is not a NIF so calling them will not cause problems in the sense that long running NIFs might.
NIFs are considered harmful
- Long-running NIFs will take over a scheduler and prevent Erlang from efficiently handling many processes.
- Short-running NIFs will still confuse the scheduler if they take more than a few microseconds to run.
A crashing NIF will take down your VM.