A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 13. WHOLE-PROGRAM ANALYSIS 111
module D = Graph.Graphviz.Dot(struct
(∗ ... ∗)
end)
The graph of callgraph functions converts a CIL call-graph into an Ocamlgraph graph that we
can use to generate a .dot le.
let graph of callgraph (cg : CG.callgraph) : SG.t =
let g = SG.create () in
H.iter (fun s n → SG.add vertex g n) cg;
H.iter (fun s n →
Inthash.iter (fun i n' →
SG.add edge g n n'
) n.CG.cnCallees
) cg;
g
The function tut13 is the entry point for this module. It computes the call-graph, converts it to a
graph for the Ocamlgraph graph library, and passses it to the graph library function that produces
the .dot le.
let tut13 (f : file) : unit =
let o = open out !Ciltutoptions.tut13out in
f | > CG.computeGraph | > graph of callgraph | > D.output graph o;
close out o
13.2 Example
The dicult part of arranging for whole-program analysis is the more complicated compilation
process. Here are two source les that we'll use to generate one call-graph:
In the rst le, we'll declare an extern function bar and dene a function foo that calls it.
../test/tut13a.c
extern int bar(int x);
int foo(int x)
{
return bar(x);
}
In the second le, we'll make an extern declaration for the function foo, and dene the function
bar that in turn calls foo. The main function simply calls bar. (Obviously, this program is a
nonsense example.)