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Static Analysis for Null Safety

1 post · Mar 2022 – Nov 2022

What this trail covers

Meta has developed and deployed Nullsafe, a static analysis tool for Java that detects NullPointerException (NPE) errors. This tool integrates into the developer workflow and has been used to make millions of lines of Java code null-safe, significantly reducing production NPE crashes and improving developer productivity. The system leverages compiler APIs, abstract syntax trees (AST), and control flow graphs (CFG) for type inference and checking, with a focus on ergonomic, scalable, and Kotlin-c

All Meta trails
  1. Retrofitting null-safety onto Java at MetaThis post introduces Nullsafe, a new static analysis tool developed at Meta to detect and prevent NullPointerExceptions (NPEs) in Java code. It details the technical approach, including the use of Java compiler APIs, AST, and CFG for flow-sensitive type inference and checking. The post highlights the importance of gradual adoption and interoperability with legacy code, demonstrating a 27% reduction in production NPE crashes on Instagram. It also contrasts Java's approach with Kotlin's built-in null safety.
  2. An open source compositional deadlock detector for Android JavaThis post introduces a new static analyzer for Android Java that detects deadlocks using abstract interpretation and compositional summarization. It scales to large codebases by processing modified files and heuristically identifying potentially deadlocking methods outside the revision. The analyzer has been deployed in CI, leading to over 200 fixes and a 54% fix rate. It is open-source as part of the Infer static analysis framework.