Pointer arithmetic demo accesses out-of-bounds memory without warning (Ch 30 / 00.pointers.ipynb)

[kwlee2025cpp]

In 30.pointers-and-memory-management/00.pointers.ipynb, the int_ptr.cpp example (cell 16) declares a single int i = 0; and then performs pointer arithmetic that dereferences memory past i:

int i = 0;
int *p = &i;
// ...
cout << "*(p + 1)  = " << ... << *(p + 1) << '\n';  // dereferencing OOB
cout << "*(p + 2)  = " << ... << *(p + 2) << '\n';  // dereferencing OOB

This is undefined behavior. The C++ standard permits p+1 (one-past-the-end pointer arithmetic) but explicitly forbids dereferencing it when p doesn't point into an array. The demo "works" because the runtime happens to allow reading adjacent stack memory, but the output is shown to students as if it were a normal pattern to learn from — which risks teaching the wrong mental model.

Suggested fix (preferred: option 1)

Option 1 — make the example valid by using an actual array:

int arr[3] = {0, 1, 2};
int *p = arr;
// (p+1) and (p+2) are now valid dereferences into arr[1] and arr[2]

Option 2 — keep the example but add a markdown cell explicitly noting this is UB, and that the output happens to read adjacent stack memory (sometimes &p and parts of the stack frame).

Option 1 is cleaner for a teaching context: students see correct pointer arithmetic without needing the UB sidebar.

Context

Surfaced during Ch 30 evaluation. Small isolated change; pairs well with the delete[] bug fix as another "first commit" candidate.