CppNorth, The Canadian C++ Conference 2025

Type erasure is a powerful concept in C++ that allows us to work with heterogeneous types while hiding their concrete details behind a generic interface. In this talk, we will explore how the C++ Standard Library employs type erasure in constructs like std::function, std::shared_ptr, and std::any to provide flexible and efficient solutions for managing types at runtime. Further, we will unveil the hidden cost of using these constructs.
We will start by building our own version of std::function, which will help demystify how it can store and call any callable object, regardless of its type. Then, we'll look at how std::shared_ptr uses type erasure to maintain type safety via dynamic dispatch of the deleter. Finally, we will delve into std::any, some times claimed the modern void*, and explore a different technique of type erasure.

Two years ago a junior developer, doing her very first "introductory" task, asked the seemingly simple question "should I check for null here?".

This, of course, resulted in a multi page response from me, starting with:

"It depends"

and ending with:

"And that's the short version. For the long version, see my hour/day presentation on whether to check for null (which is actually not about null at all, but Contracts...)"

Aha! Two years later...

This is a talk about Error Handling - but in particular those errors you didn't expect - bugs.

And yes, this is really a talk about Contracts, in particular C++26 (and beyond) Contracts. What are they, What AREN'T they, how to use them and WHY.