A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 8. DEPENDANT TYPE QUALIFIERS 66
let color includes (loc : location)
(is this : color) (in this : color)
: instr list
=
match is this, in this with
| ExactRGB c1, ExactRGB c2 → [mkColorEqInst () loc c1 c2]
| ExactRGB c1, LowerRGB c2
| LowerRGB c1, LowerRGB c2 → [mkColorLeInst () loc c2 c1]
| ExactRGB c1, UpperRGB c2
| UpperRGB c1, UpperRGB c2 → [mkColorLeInst () loc c1 c2]
| → E.error "%a: color inclusion test will always fail" d loc (!currentLoc);
[ ]
The function colors includes checks that every color of is this is included in every color of
in this. Notice how the nested List.map functions perform this all-pairs check, and builds the
resulting list of instructions with List.concat
let colors includes (loc : location)
(is this : colors) (in this : colors)
: instr list
=
if (is this = [ ] ∧ in this ≠ [ ]) ∨ (is this ≠ [ ] ∧ in this = [ ]) then
(∗ Either both have colors or neither do ∗)
E.error "%a: color mismatch" d loc loc;
L.concat (
L.map (fun c1 →
L.concat(L.map (color includes loc c1) in this)
) is this
)
8.1.6 Type-checking
Now, we can write the visitor that performs type-checking. First, we dene two functions that
extract colors from lvals and exps using colors of type. The function colors of lval adds
mappings to the context using context for struct in the case that lv accesses a structure eld.
colors of exp rst checks whether the expression is for an lval, and if so uses colors of lval
function. Otherwise it simply extracts the type of the expression and uses colors of type.
let colors of lval (c : ctxt) (loc : location) (lv : lval) : colors =
colors of type (context for struct c loc lv) loc (typeOfLval lv)