Dumping CPP symbol table stats

[Victor Norman]

I would like to tweak cpp to dump some usage stats from its symbol  
table -- like dumping which #defines were not used at all, etc.

I'm wondering if someone can help me figure out where in the code I  
would look to start to do this.

(I know that I'll need to add a command-line argument, and I'm sure I  
could figure that part out.)
Thanks.

Prof. Victor Norman
Computer Science
Calvin College
vnorman@calvin.edu
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"A designer knows he has achieved perfection not when there is nothing  
left to add, but when there is nothing left to take away." -- Antoine  
de Saint Exupéry