CppCon 2026

Native C++ types often become the format for bytes that cross a boundary: shared-memory IPC, plugin interfaces, persistent storage, or software built for more than one ABI. At that point the type is no longer just an implementation detail; it is part of a binary contract. trivially_copyable , sizeof , and code review help, but they do not answer the two questions that matter: may this type be transported as bytes at all, and do all supported ABIs give it the same object representation?

C++26 reflection can derive that evidence from the type itself. The technique builds a compile-time layout signature from ordinary C++ types, without IDL, generated stubs, or runtime inspection. The signature records the representation facts needed for byte transfer: architecture and endianness, leaf type tokens, sizes, alignments, absolute offsets, bit-fields, and pointer-like markers. It deliberately leaves out field names and source-level meaning.

With those signatures in hand, the build can enforce a gate for memcpy-style transfer. You name the boundary types and supported ABIs. Each target exports signatures, and a verification build permits direct byte transfer only when the type is byte-copy safe and the signature matches across the set. We'll walk through the workflow with static_assert checks and CI diagnostics: a fixed-width type that passes, a pointer-containing type rejected by admission, and a platform-divergent type rejected by signature comparison. The claim is intentionally narrow: representation compatibility, not semantic compatibility or schema evolution.