A CIL Tutorial - Department of Computer Science - ETH Zürich

Chapter 12
Comments
CIL has a very basic mechanism for tracking comments. In this chapter we'll see how to use
it. CIL only sees comments when they are maintained in the output of the preprocessor. The
preprocessor may be instructed to maintain comments in its output by using the -C switch to
ciltutcc. Then, the comments in the source are collected by CIL's parser and placed in the
array Cabshelper.commentsGA. commentsGA is a GrowArray.t of triples of type (Cabs.cabsloc ×
string × bool). The cabsloc is the source location of the comment. The string is the comment
itself, and the bool is set aside for application bookkeeping.
12.1 tut12.ml
In this example, we'll visit the AST and print out comments nearby instructions and statements,
taking care to only print each comment once. This will be accomplished by extracting the source
location from instructions and statements and then doing a binary search on the array of comments.
The array of comments lives in the Cabshelper module. The locations of the comments are dened
in terms of the Cabs.cabsloc record type.
module GA = GrowArray
module A = Cabs
module CH = Cabshelper
First, we'll need a few utility functions, some of which are hidden away in Tututil (e.g. functions
for ordering source locations and comments). prepareCommentArray lters out comments not from
source le fname, and sorts the results according to source location.
let prepareCommentArray (cca : comment array) (fname : string) : comment array =
cca | > array filter (fun (cl, , ) → fname = cl.A.filename)
|> array sort result comment compare
The funcion commentsAdjacent returns the indexes of at most two comments that are immediately
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