Introducing Swift Atomics

I’m delighted to announce Swift Atomics, a new open source package that enables direct use of low-level atomic operations in Swift code. The goal of this library is to enable intrepid systems programmers to start building synchronization constructs (such as concurrent data structures) directly in Swift.

→ swift.org/blog/swift-atomics/

Swift Atomics is a new open-source package enabling low-level atomic operations in Swift, allowing systems programmers to build concurrent data structures safely. As demonstrated by a thread-safe counter example using ManagedAtomic.

It bypasses Swift’s exclusivity rules for atomic access, following SE-0282’s C/C++-style memory model, and supports types like integers, Booleans, pointers, and strong references, with specialised constructs for lazy initialisation.

The package offers memory-safe ManagedAtomic and flexible UnsafeAtomic wrappers, ensuring lock-free operations but not always wait-free due to potential compare-and-exchange loops. Developers are urged to use it cautiously, isolating atomic code and leveraging Thread Sanitizer to catch issues, given its complexity and low-level nature.