C source viewer/mapper?

[noc]

I have a c program that I want to replace with a python script.

But I don't know c all that well. What I'd like to is look at a visual map
of the c program, a flowchart that draws that subroutines as blocks, points
out what variables traverse the blocks, and highlights external traffic to
sockets and ports.

A basic google search comes up empty, in spite of the fact that I'm not the
first to want such a thing. Thinkgeek offers a linux kernel map poster that
was generated by perl scripts.

So I guess that means roll my own, which means building a c interpreter, by
which time I'll have relearnt enough c to read the code in the first place,
but producing code is much cooler than simply reading code.

So, does anybody have any hints or pointers to hints that would help on this
mad errand?

Thanks
Bruce