C cross reference program

[utzoo!duke!chico!trb]

I'm interested in a good cross reference listing generator for C
programs.  Any information on wonderful cref systems will be
appreciated, but I'm especially interested in the kind of stuff that
John Lions did in his Unix commentary and his memo on "The Second
Pass of the Portable C Compiler" (nicely formatted listings of procedure
calls by caller and callee, and other goodies).