A senior engineer at Rare (Sea of Thieves) shares the practical journey of enabling /W4 /WX (warning level 4 + warnings as errors) across a 7-million-line C++ codebase built on a heavily modified Unreal Engine 4.10. The talk walks through real code review examples illustrating what specific MSVC warnings catch: narrowing conversions (C4244), forward-declared enums with unknown size (C4471), mismatched function pointer signatures (C4191), comparing enums of different types (C5054), unreferenced static functions (C4505), missing virtual destructors (C4265), signed/unsigned comparison (C4389), and unused variables (C4189). A key discovery was that a core Unreal Engine header disables over 60 warnings globally, affecting every Unreal-based game. The speaker outlines a pragmatic strategy: temporarily disable warnings-as-errors, re-enable each suppressed warning one at a time, measure unique hit counts vs. usefulness, fix what's worth fixing, and suppress the rest with explicit comments. The call to action is simple: enable more warnings in your project and let the compiler do the code review work for you.