Thread Sanitizer for Swift on Linux

The Swift language guarantees memory safety in single threaded environments. However, conflicting accesses in multithreaded code lead to data races. Data races in Swift cause unexpected behavior and can even lead to memory corruption, breaking Swift’s memory safety. Thread Sanitizer is a bug-finding tool that diagnoses data races at run time. It instruments code during compilation and detects data races when they happen during execution.

→ swift.org/blog/tsan-support-on-linux/

Swift 5.1 introduces Thread Sanitizer on Linux, enabling runtime detection of data races in multithreaded code, which can cause unexpected behaviour or memory corruption despite Swift's single-threaded safety guarantees.

To use it, add the -sanitize=thread compiler flag and build in debug mode, or with Swift Package Manager via swift build -c debug --sanitize=thread, where it reports issues like simultaneous array modifications in concurrent loops with detailed stack traces.

Fixes involve synchronisation methods, such as serial queues, to serialise access while preserving parallelism elsewhere, aligning with Swift's goal of simplifying multithreaded programming.