A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 7. TYPE QUALIFIERS 55
let warning for tcres (tcr : typecheck result) : unit =
match tcr with
| TypesMismatch(t1, t2) →
E.warn "%a: type mismatch: %a %a" d loc (!currentLoc) d type t1 d type t2
| ColorsMismatch(t1, t2) →
E.warn "%a: color mismatch: %a %a" d loc (!currentLoc) d type t1 d type t2
| TypesOkay → ()
Now, we'll visit the AST looking for places where we must check type compatibility. We must check
compatibility at assignments, casts, and parameter passing. In the case for casts, we allow constants
to be cast to a qualied type. Without this exception, it would be impossible to initialize variables
with qualied types without an error or warning. The case for function calls is left as an exercise.
class colorCheckVisitor = object(self)
inherit nopCilVisitor
method vinst (i : instr) =
match i with
| Set(lv, e, loc) →
let tcres = colorTypesCompat (typeOfLval lv) (typeOf e) in
warning for tcres tcres;
DoChildren
| Call(rlvo, fe, args, loc) → DoChildren (∗ See exercise ∗)
| → DoChildren
method vexpr (e : exp) =
match e with
| CastE(t, e) when ¬(isConstant e) →
let tcres = colorTypesCompat t (typeOf e) in
warning for tcres tcres;
DoChildren
| → DoChildren
end
The function checkColorTypes invokes the visitor colorCheckVisitor on a function.
let checkColorTypes (fd : fundec) (loc : location) : unit =
let vis = new colorCheckVisitor in
ignore(visitCilFunction vis fd)
Since gcc doesn't understand the color type attributes, we must use the colorEraserVisitor to
remove them from the program before passing the code on to it. We do this by overriding the vattr
method of the nopCilVisitor and ltering out the color attributes.