Double Pointers: Modify a Pointer Via a Function

Question

## Problem

Explain and implement passing a double pointer so a function can change the caller's pointer (e.g., allocate and return a buffer, or delete a node).

## Example
```
void alloc(char **out) { *out = malloc(64); }
```

## Constraints
- Free correctly; avoid leaks/double-free

## What Qualcomm looks for
Clear reasoning about pointer levels, heap ownership, and freeing memory for double pointers.