# Dynamic type violation Detects when an object has the wrong dynamic type. ## Overview Use this check to detect when an object has the wrong dynamic type. Dynamic type violations can cause unintended code execution. Available in Xcode 9 and later. ### Member call on instance with incorrect type in C++ In the following code, `reinterpret_cast` creates a variable with the wrong dynamic type: ```occ struct Animal { virtual const char *speak() = 0; }; struct Cat : public Animal { const char *speak() override { return "meow"; } }; struct Dog : public Animal { const char *speak() override { return "woof"; } }; auto *dog = reinterpret_cast(new Cat); // Error: dog has incorrect dynamic type dog->speak(); // Error: this call has undefined behavior ``` The method call `dog->speak()` is suspect. If the `speak` method in `Dog` is `final override`, `dog->speak()` may return `"woof"` because the optimizer can devirtualize the call; if not, it might return `"meow"`. > Note: This UBSan check requires runtime type information, and is incompatible with the `-fno-rtti` compiler flag. #### Solution Use `reinterpret_cast` sparingly, and only when it’s possible to verify that the cast object is an instance of the destination type. --- 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)