Since its introduction, the constexpr keyword in C++ has steadily evolved with each new standard, becoming an increasingly powerful tool for compile-time computation and optimization. In this article, I’ll share a real-world example of how constexpr helped optimize memory usage and improve performance for an embedded system project, showcasing its potential to transform how we approach C++ programming.

Write More C++ Code Thanks to constexpr

by Andreas Fertig

From the article:

Since the keyword constexpr and its behavior got included in C++, it has been improved in each and every new standard of the language.

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.