March 5, 2024 Holly Borla is an engineer on the Apple Swift team, and a member of the Swift Core Team, Language Steering Group, and Diversity in Swift workgroup. Swift was designed to be safe by default, preventing entire categories of programming mistakes at compile time. Sources of undefined behavior in C-based languages, such as using variables before they’re initialized or a use-after-free, are defined away in Swift. An increasingly important source of undefined behavior is concurrent code t...