Software Engineering Institute

Writing multithreaded programs is hard. Static analysis tools can help developers by allowing threading policies to be formally specified and mechanically checked. They essentially provide a static type system for threads, and can detect potential race conditions and deadlocks. This paper describes Clang Thread Safety Analysis, a tool which uses annotations to declare and enforce thread safety policies in C and C++ programs. Clang is a production-quality C++ compiler which is available on most platforms, and the analysis can be enabled for any build with a simple warning flag: -Wthread-safety.The analysis is deployed on a large scale at Google, where it has provided sufficient value in practice to drive widespread voluntary adoption. Contrary to popular belief, the need for annotations has not been a liability, and even confers some benefits with respect to software evolution and maintenance.