Andrzej continues this month with more interesting thoughts on preconditions.

Preconditions, Part 2

by Andrzej Krzemieński

In this post I will continue sharing my thoughts on preconditions. It will cover some philosophy behind the concept of preconditions (and bugs), and investigate the possibility of employing the compiler to verify some preconditions. Many people provided a useful feedback on my previous post. I will also try to incorporate it into this post.

Note that this article diverges from recommended practice in one way... it hints at the idea of throwing exceptions to report precondition violations. Instead, per C++ Coding Standards and other established guidance, prefer to use assertions to check preconditions: precondition violations are just bugs in the caller's code that should be caught at test time, assertions cause no overhead in production, and assertions fire immediately at the line of code that contains the bug without losing the call stack and other local context. Using assertions is still considered to be a best practice.