I am working on a Plugin for Frama-C, using the Value-analysis.
I simply want to print the state of the variables (values) after each statement (I think the solution is quiet easy, but I couldn't figure it out).
I got the current state with Db.Value.get_stmt_state
in the vstmt_aux
method in the visitor.
How can I now get the values of the variables?
PS: I found this post, but it didn't help, there is no real solution, and with the help of the description I was not able to do it:
How to use functions in Value.Eval_expr, Value.Eval_op etc modules of Frama-c Value plugin
Here's a concrete example of how to print, for each local and global variable, the result computed by Value before each statement in a given function (read the functions from bottom to top):
open Cil_types
(* Prints the value associated to variable [vi] before [stmt]. *)
let pretty_vi fmt stmt vi =
let kinstr = Kstmt stmt in (* make a kinstr from a stmt *)
let lval = (Var vi, NoOffset) in (* make an lval from a varinfo *)
let loc = (* make a location from a kinstr + an lval *)
!Db.Value.lval_to_loc kinstr ~with_alarms:CilE.warn_none_mode lval
in
Db.Value.fold_state_callstack
(fun state () ->
(* for each state in the callstack *)
let value = Db.Value.find state loc in (* obtain value for location *)
Format.fprintf fmt "%a -> %a@." Printer.pp_varinfo vi
Locations.Location_Bytes.pretty value (* print mapping *)
) () ~after:false kinstr
(* Prints the state at statement [stmt] for each local variable in [kf],
and for each global variable. *)
let pretty_local_and_global_vars kf fmt stmt =
let locals = Kernel_function.get_locals kf in
List.iter (fun vi -> pretty_vi fmt stmt vi) locals;
Globals.Vars.iter (fun vi _ -> pretty_vi fmt stmt vi)
(* Visits each statement in [kf] and prints the result of Value before the
statement. *)
class stmt_val_visitor kf =
object (self)
inherit Visitor.frama_c_inplace
method! vstmt_aux stmt =
(match stmt.skind with
| Instr _ ->
Format.printf "state for all variables before stmt: %a@.%a@."
Printer.pp_stmt stmt (pretty_local_and_global_vars kf) stmt
| _ -> ());
Cil.DoChildren
end
(* usage: frama-c file.c -load-script print_vals.ml *)
let () =
Db.Main.extend (fun () ->
Format.printf "computing value...@.";
!Db.Value.compute ();
let fun_name = "main" in
Format.printf "visiting function: %s@." fun_name;
let kf_vis = new stmt_val_visitor in
let kf = Globals.Functions.find_by_name fun_name in
let fundec = Kernel_function.get_definition kf in
ignore (Visitor.visitFramacFunction (kf_vis kf) fundec);
Format.printf "done!@.")
This is far from ideal, and the output is uglier than simply using Cvalue.Model.pretty state
, but it could serve as base for further modifications.
This script has been tested with Frama-C Magnesium.
To retrieve the state after a statement, simply replace the ~after:false
parameter in fold_state_callstack
with ~after:true
. My previous version of the code used a function which already bound that value for the pre-state, but no such function is exported for the post-state, so we must use fold_state_callstack
(which is incidentally more powerful, because it allows retrieving a specific state per callstack).