With P2900, we propose to add contract assertions to the C++ language. This proposal is in the final stages of wording review before being included in the draft Standard for C++26. It has been suggested by some members of the C++ standard committee that this feature is too large, too complicated, and hard to teach. As it turns out, the opposite is true: contract assertions are actually very simple and can be explained in just five minutes. In this blog post, we will do exactly this!

As the name says, contract assertions are assertions — correctness checks that the programmer can add to their code to detect bugs at runtime. So they’re just like the existing assert macro, except they’re not macros (which fixes a bunch of problems) and they’re way more flexible and powerful!