In the article about Standard Library hardening, we looked at checks for invalid Standard Library container access and other broken preconditions. I mentioned that those requirements are expressed in terms of “contracts”. But what about our code?
In this post, we’ll explore contracts from C++26. We’ll start with a simple cassert, move the requirement into the function itself, and see how to check results. We’ll also look at declarations and definitions, compiler options, and a few details that can surprise you.
The function expects a valid index. If the condition is false, assert prints a diagnostic message and terminates the program. However, this only happens when assertions are enabled. Defining NDEBUG disables the check and basically removes the check from the code.
