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C++20 introduces a new feature to the language: modules. They replace the plain-text symbol declarations in header files with a module file that will be precompiled to an intermediary binary format, greatly reducing the build time.
I wanted to write about how to use C++ modules over three years ago. Despite the fact that modules were already accepted as part of the C++20 specification, the support of the C++ ecosystem was still nowhere near ready to use this feature. Fortunately, a lot has changed since the 1st edition of this book, and with the release of CMake 3.28 the C++20 modules are officially supported (experimental support was available since 3.26). Three years may seem like a long time to implement a single feature, but we need to remember that it's not only up to CMake. Many pieces of the puzzle have to come together and work well. First, we need compilers to understand how to deal with modules, then buildsystems...
