dereferencing the null pointer

Question

int* p = 0;
int* q = &*p;

Is this undefined behavior or not? I browsed some related questions, but this specific aspect didn\'t show up.

Answer 1

Yes, dereferencing the null pointer is undefined behavior. Integer constant 0 in a pointer context is the null pointer. That's it.

Now, if your second line was int *q = p; that would be a simple pointer assignment. If the compiler removes the &* and reduces the dereference to an assignment, you're OK.