A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 7. TYPE QUALIFIERS 53
let color strings = [redStr; blueStr; greenStr; ]
As mentioned in a previous chapter, it is useful to have functions that convert a type to and from
a string. The function string of color returns redStr, blueStr, or greenStr as appropriate.
let string of color (c : color) : string =
match c with
| Red → redStr
| Blue → blueStr
| Green → greenStr
The function color of string returns the color corresponding to the string cs it gets as input.
let color of string (cs : string) : color =
match S.lowercase cs with
| s when s = redStr → Red
| s when s = blueStr → Blue
| s when s = greenStr → Green
| → E.s(E.bug "Expected a color string, got: %s" cs)
The function isColorType returns true when a type is qualied by a particular color attribute. The
function isTypeColor the same with the order of the arguments reversed. The next three functions
tell if a type is qualied by a particular color. These functions to largely similar things, but they'll
be useful in dierent situations.
isColorType is written with the function hasAttribute, which comes from the core Cil module.
It returns true when a list of attributes contains an attribute with the given name. typeAttrs
extracts the attributes from a type. Attributes are one of the extensions to C accepted by gcc. CIL
parses these attributes, even custom attributes not understood by gcc, and includes them in its
AST attached to types, elds, functions, formal parameters, and blocks of code. All we care about
for now, though, is whether or not a type is qualied by one of the colors.
let isColorType (cs : string) (t : typ) : bool =
hasAttribute cs (typeAttrs t)
let isTypeColor (t : typ) (cs : string) : bool = isColorType cs t
let isRedType : typ → bool = isColorType redStr
let isBlueType : typ → bool = isColorType blueStr
let isGreenType : typ → bool = isColorType greenStr
The function colors of type takes a type and returns a list of colors that qualify the type.