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[Frama-c-discuss] Inductive definition of reachability in an array-implemented list.

  • Subject: [Frama-c-discuss] Inductive definition of reachability in an array-implemented list.
  • From: eric.jenn at (JENN Eric)
  • Date: Thu, 04 Jun 2009 15:52:50 +0200

Dear Colleagues,

I am puzzled by the following example, which is a slightly adapted 
version of a bigger piece of code I am working on:

typedef int T_ID;

typedef struct
  T_ID          next;
} T_ELT;


// Definition of reachability
    inductive is_reachable{L}(T_ID start_id, T_ID end_id) {
    case is_length_one{L}:
     \forall T_ID alert_id;
        (0 <= alert_id < 4) ==>
          is_reachable(alert_id, alert_id);
     case is_path_non_one{L}:
     \forall T_ID start_id, T_ID end_id;
       ((0 <= start_id < 4) && (0 <= end_id < 4)) ==>
            is_reachable(LIST[start_id].next, end_id) ==>
                is_reachable( start_id, end_id);





void f()
  LIST[0].next = 1;
  LIST[1].next = 2;
  LIST[2].next = 3;
  LIST[3].next = -1;


The PO for the second postcondition is verified (hopefully).
The PO for the first post-condition can't be discharged neither by Ergo, 
nor by Simply, nor by Z3.

(As usual,) I am certainly missing something obvious, but what?

Thanks for your help



By the way...
A few proposals for "improvements" to gWhy:
- It would be nice if one could select provers on a per-PO basis and 
save this configuration, so as to replay the proof automatically with 
the appropriate prover.
- It would be nice if it were possible to try another prover when a 
proof fails with a given prover (the one selected using the menu).
- It would be nice if we could benefit from multi-cores to start as many 
provers as there are cores, automatically (that what I do manually...).

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