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[Frama-c-discuss] Unable to prove assigns clause for array

  • Subject: [Frama-c-discuss] Unable to prove assigns clause for array
  • From: Boris.Hollas at de.bosch.com (Hollas Boris (CR/AEY1))
  • Date: Mon, 30 Mar 2009 18:12:42 +0200
Hello,

I'm trying to verify the following code:


/*@ requires \valid(a+ (0..aLength-1));
    requires aLength >= 2;
    assigns a[0..aLength-2];
*/
void foo(int a[], int aLength) {
  int j;
  const int x;

  x = a[aLength-1];
  /*@    loop invariant x == a[aLength-1];
         loop invariant 0 <= j;
  */
  for(j=0; j<aLength-1; j++) {
    a[j] = 0;
  }
}


However, I'm unable to prove assigns a[0..aLength-2]. I recall that David Mentre had a similar problem proving an assigns clause on arrays.

In addition, Simplify (but not Alt-Ergo) is unable to check  x = a[aLength-1] for arithmetic overflow.

Any suggestions?

- Boris