0001495: crash - Frama-C Bug Tracking System

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0001495

Frama-C

Kernel > ACSL implementation

public

2013-10-01 18:03

2014-02-05 17:40

Reporter

alessioiotti

Assigned To

virgile

Priority

normal

Severity

minor

Reproducibility

always

Status

assigned

Resolution

open

Platform

OS Version

Product Version

Frama-C Fluorine-20130601

Target Version

Fixed in Version

Summary

0001495: crash

Description

The full backtrace is:
Raised at file "hashtbl.ml", line 254, characters 18-27
Called from file "hashtbl.ml", line 262, characters 22-38

The program raise an unexpected error trying to prove an ensures clause with behavior using a logic function.

The code is the following:

/*@
  @ predicate IsValidRange(int* a, integer n) =
  @ (0 <= n) && \valid(a+(0.. n-1));
  @
  @
  @ predicate IsEqual{A, B}(int* a, int* b, integer n) =
  @ \forall integer i; 0 <= i < n ==> \at(a[i], A) == \at(b[i], B);
  @
  @ logic integer MinIndex(int* a, int* b, integer starting_index, integer count) =
  @ ((count <= 0 || starting_index >= count) ? -1 :
  @ (starting_index == count)) ? -1 :
  @ (a[starting_index] != b[starting_index]) ? starting_index : MinIndex(a, b, (starting_index + 1), count);
*/

/*@ requires \valid(a+(0..n-1)) && \valid(b+(0..n-1)) && (n >= 0);
  @ assigns \nothing;
  @ behavior equal:
  @ assumes IsEqual{Here, Here}(a, b, n);
  @ ensures \result == n;
  @ behavior not_equal:
  @ assumes !IsEqual{Here, Here}(a, b, n);
  @ ensures \result == MinIndex(a, b, 0, n);
  @ complete behaviors;
  @ disjoint behaviors;
*/
int mismatch(const int* a, const int* b, int n) {
    /*@ loop assigns i;
      @ loop invariant (0 <= i <= n) && IsEqual{Here, Here}(a, b, i);
      @ loop variant n - i;
    */
  for (int i = 0; i < n; i++)
    if (a[i] != b[i])
      return i;

  return n;
}

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Notes
(0004511) virgile (developer) 2014-02-05 17:40	issue lies in the fact that MinIndex is recursive and uses an implicit label, which fails to be propagated in the recursive call. A work around is to explicitely declare MinIndex as taking a label argument and to pass it in the recursive call.

Issue History
Date Modified	Username	Field	Change
2013-10-01 18:03	alessioiotti	New Issue
2013-10-01 18:03	alessioiotti	Status	new => assigned
2013-10-01 18:03	alessioiotti	Assigned To	=> correnson
2014-02-05 17:37	virgile	Assigned To	correnson => virgile
2014-02-05 17:37	virgile	Category	Plug-in > wp => Kernel > ACSL implementation
2014-02-05 17:40	virgile	Note Added: 0004511