A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 9. TYPE QUALIFIER INFERENCE 76
The function findColorNodes invokes the nodeColorFinder visitor on the le f with the graph g.
let findColoredNodes (f : file) (g : graph) : unit =
let vis = new nodeColorFinder g in
visitCilFile vis f
The function colors equal ensures that every color of c1 is somewhere in c2 and that every color
of c2 is somewhere in c1. That is it checks that the lists have the same elements.
let colors equal (c1 : colors) (c2 : colors) : bool =
L.for all (fun c → L.mem c c2) c1 ∧
L.for all (fun c → L.mem c c1) c2
Now that the graph has been seeded by a few type qualiers, we can see where else in the graph
they must ow. We'll accomplish this by doing the following. First, we put all the nodes in the
graph into a queue. Then, for each node that we pop o the queue, we'll nd the least-upper-bound
of the qualier on the node itself along with the qualiers on the nodes for incoming edges; these are
the types that it must include. If the least-upper-bound qualier is dierent, we'll assign the new
qualier to the node, and then add the nodes on outgoing edges to the end of the queue. When the
qualier lattice has nite height, as it does here, we can be sure that the algorithm will terminate.
The function enqueueNodes places each of the nodes in our graph on a queue and returns the
queue.
let enqueueNodes (g : graph) : int Q.t =
let q = Q.create () in
A.iteri (fun i → Q.add i q) g;
q
The function processNode folds over the incoming edges of a node, computing the least-upperbound
of the types on the origin nodes. If the result is dierent from the starting type, it adds the
new type to the graph and return true. Otherwise it returns false.
let processNode (g : graph) (id : int) : bool =
let c' =
L.fold left (fun c id' → list union c g.(id').ncolors)
g.(id).ncolors g.(id).incoming
in
if ¬(colors equal g.(id).ncolors c') then begin
g.(id).ncolors ← c';
true
end else false
The function processQueue applies processNode to each node of the graph g on queue q. If
processNode for some node returns true, it adds the destinations of the node's outgoing edges to
the end of the queue.