A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 14. IMPLEMENTING A SIMPLE DSL 116
let hasArgAttr : attributes → bool = hasAttribute argStr
let hasAssertAttr : attributes → bool = hasAttribute assertStr
let hasMandatoryAttr : attributes → bool = hasAttribute mandatoryStr
The functions isArgType, and isMandatoryType return true when their argument types have the
indicated attributes.
let isArgType (t : typ) : bool = t | > typeAttrs | > hasArgAttr
let isMandatoryType (t : typ) : bool = t | > typeAttrs | > hasMandatoryAttr
The function getAssertAttr returns the attribute parameter when the type has a "ciltut assert"
attribute, and otherwise throws an exception.
let getAssertAttr (t : typ) : attrparam =
match filterAttributes assertStr (typeAttrs t) with
| [Attr( , [ap])] → ap
| → E.s (E.error "Malformed %s attribute: %a" assertStr d type t)
The function string of exp extracts a string literal from an expression and returns it as an OCaml
string. If the expression is NULL, it returns the empty string. If the expression is not a string, it
raises an exception. We'll use it to extract structure elds for the argument type.
let rec string of exp (e : exp) : string =
match e with
| Const(CStr s) → s
| z when z = zero → ""
| CastE( , e) → string of exp e
| → E.s (E.error "Expected string literal: %a" d exp e)
The function name of argname extracts the name of the argument from the name of the instance
of the argument description structure.
let name of argname (s : string) : string =
if S.length s < 8 then
E.s (E.error "Invalid argument name: %s" s);
S.sub s 8 (S.length s − 8)
Since we're using attributes to express the assertions about arguments, we'll need a few functions
from Chapter 8 that we'll use to compile the attribute parameters. The function req of exp
extracts the attrparam for an argument assertion from a CastE expression, and compiles it using
T.exp of ap. The context c holds all of the global variables, so the assertion can also refer to other
command line arguments.