LLVM 21 Under Static Analysis: Bugs, UB Risks, and Refactor Fallout

A fresh PVS-Studio scan of LLVM 21 (core project, excluding major subprojects) highlights a pattern of real-world C++ pitfalls: copy-paste conditions, dead stores, unreachable branches, enum mix-ups, and edge-case undefined behavior. The article walks through 20 concrete warnings across architectures and subsystems, explains why each is likely a bug (or at least suspicious), and proposes targeted fixes—showing how even elite codebases accumulate subtle issues between releases, especially amid fast-moving refactors and “revert to green” merges.