# Null reference creation and null pointer dereference Detects the creation of null references and null pointer dereferences. ## Overview In Xcode 9 and later, you can use this check to detect the creation of null references and null pointer dereferences. Dereferencing a null pointer always results in undefined behavior and can cause crashes. If the compiler finds a pointer dereference, it treats that pointer as nonnull. As a result, the optimizer may remove null equality checks for dereferenced pointers. ### Creating a null reference in C++ The following example demonstrates how to create a null reference. References in C++ must be nonnull: ```occ int &x = *(int *)nullptr; // Error: null reference ``` #### Solution Use a pointer instead. ```occ int *x = nullptr; // Correct ``` ### Member access through a null pointer in C++ The following code makes a member call on an object with a null address. The compiler may remove the null check on the `this` pointer because it requires the pointer to be `nonnull`. ```occ struct A { int x; int getX() { if (!this) { // Warning: redundant null check may be removed return 0; } return x; // Warning: 'this' pointer is null, but is dereferenced here } }; A *a = nullptr; int x = a->getX(); // Error: member access through null pointer ``` > Important: Always avoid null checks on the `this` pointer. #### Solution Avoid calling methods on null objects. --- 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)