A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 14. IMPLEMENTING A SIMPLE DSL 115
getopt long and uses sscanf to parse any options the arguemnts might have.
14.1.1 Specication Extraction
The argument type is where we'll collect the information the programmer gives us about the command
line arguments.
type argument = {
mutable argName : string; (∗ The name of the argument, i.e. -- ∗)
mutable argType : typ; (∗ The type of the argument ∗)
mutable argShort : string; (∗ The short form of the argument, i.e. -n ∗)
mutable argHelp : string; (∗ The help message for the argument ∗)
mutable argFmt : string; (∗ The format specier for sscanf ∗)
mutable argDef : exp; (∗ The default value of the argument ∗)
mutable argReq : exp; (∗ An assertion about the argument ∗)
mutable argOpt : bool; (∗ Whether the argument is optional ∗)
mutable argVi : varinfo; (∗ The global varialbe for the argument ∗)
mutable argGot : varinfo; (∗ Global variable indicating whether the argument was given ∗)
mutable argOption : bool; (∗ Whether the argument as a parameter ∗)
}
The function makeArgument makes a fresh argument initialized with dummy values.
let makeArgument () = (∗ ... ∗)
Now that we've dened the argument type, we can write utility functions for extracting information
from type attributes. In particular, structure types that should be interpreted as argument speci-
cations are annotated with the ciltutarg type attribute. Also, we extract the parameter to the
ciltut assert attribute on the type of the requires eld of the argument structure to be used as
an assertion that must be true of the argument, e.g. intarg > 0 in the example above.
As usual, we begin by dening some global variables for the string constants, along with a list
of the strings.
let argStr = "ciltutarg"
let assertStr = "ciltut assert"
let mandatoryStr = "mandatory"
let attr strings = [argStr; assertStr; mandatoryStr; ]
The functions hasArgAttr, hasAssertAttr, and hasMandatoryAttr return true if their arguments
have the indicated attributes.