GCC 16.2 optimizes C++ off-by-one to always return true

The article explains how C++ undefined behavior can cause compilers to remove preceding valid code and why C++26 adopts observable checkpoints to prevent this behavior. The author details how compilers optimize code when undefined operations are reached and how new mechanisms like std::observable_checkpoint protect preceding observable actions. However, the author notes that checkpoints do not fix the underlying bugs or protect unobservable computations. Open article →