To improve the output that is available a modified version of the GNU CPP V2.7.2 is supplied (named cxref-cpp).
This modified C preprocessor allows for a finer control over some features of the preprocessing that are not important for a compiler. In a standard preprocessor, the preprocessor directives are intended for use only by the preprocessor, so passing the information through is not important.
With cxref-cpp, there are two features that are different to the standard GNU CPP: