Since its introduction, constexpr in C++ has evolved significantly, offering powerful ways to optimize code at compile-time. This article shares a real-world story of using constexpr to dramatically reduce memory usage and code size in an embedded system, showcasing its potential to improve both performance and efficiency.

Write More C++ Code Thanks to constexpr

by Andreas Fertig

From the article:

I'm a big fan of constexpr and am not alone. Jason Turner is also very vocal, having coined the term "constexpr all the things".

Well, demonstrating the powers of constexpr is nonetheless something difficult. I know that from my training classes and various consulting contracts. Today, I'd like to share a story from back in time when a customer hired me to consult. They did develop an embedded system and ran out of memory. Not during run-time, but before. The features they wanted to put in the chip were too big in code size and somewhat RAM.

Initial constexpr-free example

They used a class I've seen a couple of times in embedded systems with some variations. A string brings its memory picky-back.