Accessing an out-of-bounds index

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It is undefined behavior to access an index that is out of bounds for an array (or standard library container for that matter, as they are all implemented using a raw array):

int array[] = {1, 2, 3, 4, 5};
array[5] = 0;  // Undefined behavior

It is allowed to have a pointer pointing to the end of the array (in this case array + 5), you just can’t dereference it, as it is not a valid element.

const int *end = array + 5;  // Pointer to one past the last index
for (int *p = array; p != end; ++p)
  // Do something with `p`

In general, you’re not allowed to create an out-of-bounds pointer. A pointer must point to an element within the array, or one past the end.

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