I have made a similar tool that is a lot more hacky, but does not require compilation or preprocessing of the source (and is this not reliant on any single comp

I have made a similar tool that is a lot more hacky, but does not require compilation or preprocessing of the source (and is this not reliant on any single compiler): https://github.com/orlp/iwyu https://github.com/orlp/iwyu. It also does nothing smart, it is user trained. Every symbol prefixed with a namespace you are interested in will be presented to you, and you must tell it where to find the symbol. Any other symbols will be ignored.