What this topic actually controls

Arrays and pointers are efficient because they expose memory directly, and risky for exactly the same reason. The objective is not to avoid pointers, but to bind every pointer to clear lifetime and bounds metadata.

Key low-level points:

• Array indexing and pointer arithmetic are equivalent at the address level, but API contracts often hide this fact.
• Dereference safety requires valid address, valid lifetime, and correct alignment simultaneously.
• Most memory bugs come from stale ownership assumptions, not from syntax mistakes.

Quantitative behavior you should be able to compute

Address of element i in a contiguous array:

Where:

• $base(a)$: starting address of array
• $i$: zero-based index
• $T$: element type

Valid index interval:

Where:

• $n$: element count

Design path from requirement to implementation

Design pointer APIs as (ptr, len) pairs unless there is a stronger invariant.

Perform bounds check before dereference in every external input path.

Track ownership transitions explicitly when memory is handed across module boundaries.

Use debugger watch expressions to confirm pointer movement during loops.

Where real projects usually break

Any pointer used after free is invalid even if address value still prints.

Null checks do not replace bounds checks for non-null pointers.

Do not assume two pointers alias or do not alias without proof.

Review pointer arithmetic with element size, not byte intuition.

Good pointer code is auditable: each pointer has a source, a valid range, and a clear owner at every point in execution.