CppCon 2026

Many codebases contain several spots of type punning, and unfortunately a whole lot of those are incorrect and undefined behavior. While many current versions of compilers seem to do the correct thing, they might no longer do that tomorrow. Safety considerations wants to reduce/eliminate UB.

It might be worthwhile to inspect your reinterpret_cast constructs, most probably they are wrong. In this talk we will inspect what is wrong about those, we will learn about alignment, strict aliasing, object lifetime. 3 areas which might flag a red card on our type punning constructions.

Luckily the language evolved and gave us more tools to do it correctly, things like memcpy, memmove, bit cast, start lifetime_as, launder. It does however remain a dark corner and a dangerous territory to wander in. Because let's face it, zero copy is something we love in C++, and those bytes that came from the network, really are an array of integers, array of coordinates, ... Compiler, trust me, I know what I am doing. Am I?