A CIL Tutorial - Department of Computer Science - ETH Zürich

CHAPTER 1. THE AST 13
1.2 Printing the AST
The function tut1FixInstr also uses CIL's logging and pretty-printing features. The call to E.log
causes messages to be printed to stdout. It is similar to Printf.printf from the OCaml standard
library with a few dierences that are documented in cil/ocamlutil/errormsg.mli. Most
importantly, you can print elements of the CIL AST by using the %a format specier. Then, corresponding
to that format you must supply two arguments: a function (unit → α → doc), and such
an α that you want to print. Functions like this for the AST elements are dened in cil.ml (e.g.
Cil.d exp for Cil.exp's). Functions for building objects of type doc are available in the Pretty
module documented in cil/ocamlutil/pretty.mli.
1.3 test/tut1.c
The module tut1.ml deletes writes inside functions named target to global variables named
deleted. Thus, the function target below will return 37.
# include
int deleted = 37;
../test/tut1.c
int target()
{
int l;
deleted = 0;
l = deleted;
return l;
}
int main()
{
int r;
r = target();
printf("r = %d\n", r);
return 0;
}
We can build this le with the following command:
$ ciltutcc --enable-tut1 -o tut1 test/tut1.c
test/tut1.c:14: Deleted assignment: #line 14 "test/tut1.c"
deleted = 0;
Using the log message emitted by tut1FixInstr, ciltutcc informs us that it has removed an
assignment to deleted. Now, we can run the resulting program: