Writing to nios reset vector

Hello!

I have just found rather stupid bug when I was dereferencing NULL pointer and had a nios reset.

I'm actually need some help to clarify (for better understanding nios) what actually happend and how nios is reseting.

Some example code.

some_struct_type1 * a = NULL;

some_struct_type2* struct1 = a->p_struct1;

*(struct1->p_int) = 0xfeed;

So why I have restart and not simple memory corruption?