C++ Modules Cyclic Dependencies

The mother of all frustrations

Motivation

The cyclic dependency problem in C++ modules is a well-recognized issue in the C++ community, particularly as modules (introduced in C++20) are increasingly adopted. While there is limited formal academic research or large-scale empirical studies specifically quantifying the pervasiveness of cyclic dependencies in C++ modules, there is substantial anecdotal evidence and discussion within developer communities, particularly on social media platforms like Twitter, Stack Overflow, Reddit, and programming forums.

Cyclic dependencies in C++ modules are particularly harmful in several key scenarios, as they can break the fundamental benefits of modules, such as improved encapsulation, faster compilation, and clear dependency management.