Writing into 0x0 is creating System Exception in m33 whereas in m4 it is not


We are using one of the m4-based microcontrollers. Unfortunately, it is reaching the End of life. Our Team decided to go with a cortex  m33-based microcontroller.

In that, I found that 

int *ptr;

This piece of code is not creating any Exceptions in m4 but in m-33 it is creating. Is this expected from the m-33 processor? 

If we migrate from m4-based controller to m33 what are thing we need to take care of?

Thanks in Advance