The ABA problem in concurrent programming occurs when a shared variable changes from A → B → A, making it appear unchanged to a thread performing a compare-and-swap (CAS) operation. This can lead to unintended behavior because the underlying object at address A may no longer be the same.

In Rust, solving the ABA problem often involves techniques like:

Tagged Pointers with Versioning: Each pointer is paired with a version number, ensuring that even if the same memory address is reused, outdated versions are detected.

Epoch-Based Reclamation: This method tracks memory usage across threads and prevents premature deallocation.

Hazard Pointers: A safe memory reclamation technique that ensures a thread accessing a shared object is aware of potential modifications