CppCon 2026

Today's world runs on C++. That's because, in domains requiring scale, performance, low latency, and fine-grained control over concurrency, C++ is second to none! Yet in recent years, a growing concern has emerged: C++ programs are often considered unsafe — not because of programmer negligence, but because the language itself provides insufficient mechanisms to prevent or reliably detect undefined behavior (UB).

For those financially and technically invested in C++, its current lack of language safety raises a fundamental question: How can we evolve ISO C++ to be UB-safe without necessarily sacrificing runtime performance, and without breaking backward compatibility with existing, valid C++ code?

In this talk, we begin by motivating an overall approach to UB-safety that starts from a simple but uncompromising premise: each individual potential source of UB must be able to be detected via runtime checking. Crucially, this approach eliminates the notion of "safe" and "unsafe" regions of a program — there is no place where UB can hide, and no need to switch languages, subsets, or tools to achieve comprehensive coverage.

We then examine how the C++26 contracts facility provides the essential foundation for transforming optional runtime checks into the practical, scalable mechanisms to eliminate UB bugs in production software. Contracts give developers fine-grained control over where and when checking occurs, allowing runtime overhead to be spent where it is affordable or most valuable — such as in new, rarely executed, or security-critical code. These decisions naturally evolve over time, as long-running checks that never fire may no longer justify their cost.

Finally, we outline the concrete steps of an incremental journey toward reducing undefined behavior in ISO C++. The result is a model of UB-safety — rooted in C++26 contracts and optional runtime checking — that is competitive with, and in key respects stronger than, approaches taken by other high-performance languages. Most importantly, this model applies not only to new code, but to the vast body of existing C++ software already in the wild.

Modern C++ gives developers powerful tools to write cleaner, safer, and more expressive code — but many production codebases still suffer from excessive boilerplate, repetitive patterns, and verbose implementations inherited from older C++ styles.

This talk explores practical modern C++ techniques that significantly reduce lines of code while preserving readability, maintainability, and runtime performance.

Through real-world examples, we will refactor traditional C++ implementations using features such as ranges, structured bindings, constexpr, concepts, CTAD, lambdas, std::optional, std::variant, and std::expected. We will examine where these features genuinely improve code quality — and where they can accidentally hurt clarity or performance if misused.

The session also goes beyond syntax improvements by analyzing generated assembly, compiler optimizations, allocations, and benchmark results to validate whether “shorter” code truly remains zero-cost.

Attendees will leave with practical patterns they can immediately apply to modernize existing codebases, reduce unnecessary complexity, and write more expressive C++ without sacrificing performance.