IfcPlusPlus is an open source C++ class model, as well as a reader and writer for IFC files in STEP format. Features: Easy and efficient memory management using smart pointers. Parallel reader for very fast parsing on multi-core CPU's. Additionally, there's a simple IFC viewer application, using Qt and OpenSceneGraph. It can be used as starting point for all kinds of applications around the open building model standard IFC.
Why do you think that https://github.com/sarah-ek/faer-rs is a good alternative to ifcplusplus