Swift’s support for safe and efficient systems programming relies on features for explicit ownership and lifetime analysis of values. These features must be designed to fit cleanly into a language that has long prioritized simple, low-friction application development. In this talk, I will discuss the ongoing design of these features and the constraints we’ve encountered adding them to an existing, widely-used language. In particular, I will talk about how source compatibility, ABI stability, and the desire to preserve the usability of the language for less performance-sensitive programmers have impacted the design. I will also talk about the problems we’re currently looking at and some interesting active areas of research.

John McCall is a programming language designer and compiler engineer at Apple, where he has worked since 2008 on Swift, Clang/LLVM, Objective-C, and C++. He currently chairs Swift’s Language Steering Group and is a core contributor to major parts of the Swift compiler, including SIL, LLVM IR generation, the language ABI, and the runtime. Before joining Apple, he received an M.S. in computer science from Portland State University and earned a B.S. in mathematics from Carnegie Mellon University.