A CIL Tutorial - Department of Computer Science - ETH Zürich
A CIL Tutorial - Department of Computer Science - ETH Zürich
A CIL Tutorial - Department of Computer Science - ETH Zürich
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CHAPTER 8. DEPENDANT TYPE QUALIFIERS 62<br />
8.1.2 Context for compiling type qualiers<br />
We would like to allow our color type qualiers to refer to C expressions. Therefore, in order<br />
to interpret them, and to compile them into our OCaml type (color), we require a context to<br />
translate names into <strong>CIL</strong> expressions. Instances <strong>of</strong> the ctxt type simply map strings to <strong>CIL</strong><br />
expressions. Here, we'll also write some functions for looking up strings in the context, adding<br />
variables, expressions, and elds to a context, and extending a context so that type qualiers may<br />
refer to global varialbes, local variables, and structure elds. We also include a function so that the<br />
types <strong>of</strong> formal parameters may refer to other formal parameters.<br />
type ctxt = exp SM.t<br />
let exp <strong>of</strong> string (c : ctxt) (s : string) : exp = SM.find s c<br />
let ctxt add var (c : ctxt) (vi : varinfo) : ctxt = SM.add vi.vname (v2e vi) c<br />
let ctxt add exp (c : ctxt) (s : string) (e : exp) : ctxt = SM.add s e c<br />
let ctxt add field (blv : lval) (c : ctxt) (fi : fieldinfo) : ctxt =<br />
SM.add fi.fname (Lval(addOffsetLval (Field(fi, NoOffset)) blv)) c<br />
The function context for globals generates a fresh context containing mappings for the global<br />
variables. It does this by folding over the list <strong>of</strong> globals in f.globals and using ctxt add var when<br />
encountering a global variable declaration or denition.<br />
let context for globals (f : file) : ctxt =<br />
L.fold left (fun c g →<br />
match g with<br />
| GVarDecl(vi, ) → ctxt add var c vi<br />
| GVar(vi, , ) → ctxt add var c vi<br />
| → c)<br />
SM.empty f.globals<br />
The function context for locals extends a context with mappings for local variables and function<br />
parameters.<br />
let context for locals (c : ctxt) (fd : fundec) : ctxt =<br />
L.fold left ctxt add var c (fd.slocals @ fd.sformals)<br />
Used at a call site, the function context for call extends a context with mappings from formal<br />
parameters to actual parameters. Since there may be more actuals than formals, we use<br />
list take dened in Tututil to limit the mapped actuals to the number <strong>of</strong> formals. Then, we<br />
map ctxt add exp over the lists. It is used for resolving function argument types at a call site,<br />
which may refer to the other function arguments.
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