This has always been a problem in talking about modules in C++. Everyone has a different idea of what a module is. Currently every compiler except MSVC plans

This has always been a problem in talking about modules in C++. Everyone has a different idea of what a module is. Currently every compiler except MSVC plans to make module files version locked. Different versions of the same compiler will use different module files. Personally I find little value in portable module files, as you need to be able to rebuild modules anyway to handle pretty much any change to compile flags.