To improve the output that is available a modified version of the GNU CPP V2.6.3 is supplied (named cxref-cpp).
Some comment styles are only available if cxref-cpp is used, see the ``Example Special Comments'' section of this README.
The #include filenames are also full pathnames if cxref-cpp is not used.
To enable this option, the Makefile for cxref must be modified when cxref is compiled, the variable CPP_TO_USE must be set to point at the place where the C preprocessor is to be installed. If CPP_TO_USE is defined to an empty value then ``gcc -E -C -dD'' is used as the C preprocessor and the extra features are not available. To see which option is enabled, run cxref with no arguments, this prints the name of the preprocessor that is used, if the command is ``cxref-cpp'' then the option is enabled.