One of the codebases that I work on is theoretically C++, but if you peer under the hood, it looks more like 1990-vintage C. It’s 500 KLOC of almost purely procedural code, with lots of structs and few true objects. More dusty and brittle than I’d like.

Image credit: Tim Gillin (Flickr)
I am not a C++ bigot; I first began to do serious, professional coding in C, not long after this codebase got its start. I understand the C-isms pretty well. And although I think Linus got carried away in his rant about the ugliness of C++, I can appreciate the ways that lean C sometimes makes its descendant look ugly and inefficient. (Though C++11 and 14 are making this less true…)
This means that I don’t consider the C-like style of this particular codebase a fatal flaw, in and of itself.
However, since my early coding adventures I’ve been converted to the advantages of OOP for complex projects and large teams, and I’ve also accumulated a lot of battlescars around multithreading. Our codebase needs OOP to solve some encapsulation antipatterns, and it needs RAII and C++11-style mutexing in the worst way. Its old, single-threaded mindset makes far too many things far too slow and error-prone.
A few months ago, we decided to make an investment to solve these problems.
To do it right, I had the team add a story to our scrum backlog about making the codebase const-correct. And therein lies a tale worth recounting…