The compiler won't be a build system? I'm not quite so sure. We already have -MD in gcc to emit Makefile rules for the dependencies of the current file. It's not much of a stretch to propose a similar flag to emit a list of required modules. In fact the very same flag could emit a foo.bmi target requirement when you "import foo" and your Makefile should have foo.bmi as one of the products of compiling the foo module. You could also have a similar flag that tells you what modules are built from the current cpp file given some compiler options.