Source code cross referencing tools?

This list is a mix of both on-topic and off-topic stuff. If you notice the email alias it was sent to, it went to the "both" list. There had been talk of separating the lists but one still feeds the other. Believe me, I don't want to be the catalyst or the target of scorn at all. Now that I'm on the defensive, the relevance is that this tool is being used to analyze source code of a program that's part of a 6502-based emulation project I'm working on. I believe that the 6502 qualifies as "classic" and so does "emulation of old machines". I didn't feel it necessary to justify the need for the info (to which no less than 10 people have responded with very helpful links and pointers -- thanks) since (1) it is for a classic-related project and (2) I've been on this list since 1998 and the UWash days and people know I don't ask meaningless, time-wasting questions. I feel I can ask an occasional question of one of the most knowledgeable group of technology people I know. Sorry to have bothered you. Thanks. Rich -- Rich Cini Collector of Classic Computers Build Master and lead engineer, Altair32 Emulator http://www.altair32.com http://highgate.comm.sfu.ca/~rcini/classiccmp