# Out-of-bounds array access Detects out-of-bounds access of arrays. ## Overview Use this check to detect attempts to access indexes that exceed the array’s bounds. Out-of-bounds array accesses have undefined behavior, and can result in crashes or incorrect program output. Available in Xcode 9 and later. > Note: This check doesn’t detect out-of-bounds accesses into heap-allocated arrays. ### Out-of-bounds array access in C In the following example, out-of-bounds access of `array` occurs on the last iteration of the loop: ```occ int array[5]; for (int i = 0; i <= 5; ++i) { array[i] += 1; // Error: out-of-bounds access on the last iteration } ``` #### Solution Ensure that accessed indexes don’t exceed the array’s bounds. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)