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[Frama-c-discuss] z3 failure

A problem is double. The same program with int arrays for arguments is
successfully proved by Z3.


---
Eugene Kornykhin,
Lomonosov Moscow State University

On 7 October 2013 01:06, Stephen Siegel <siegel at udel.edu> wrote:

> I have a very simple example (below) which I want to verify with frama-c +
> Jessie.  The VCs are discharged easily by Alt-Ergo, CVC3, and CVC4.
>  However they are not discharged by Z3.  This is surprising since Z3 is a
> very powerful prover.   I'm wondering if anyone has any idea what is going
> on, or how to look into it.
>
> I am using Z3 4.3.1.  There are two VCs.  One, "copy_safety" is discharged
> by Z3 very quickly.  The other, "copy_ensures_default" runs forever. I've
> moved the timeout to 60 seconds, and it still times out.
>
> BTW, this warning appears with both VCs:
>
> WARNING: '=' cannot be used in patterns
>
> Here is the program copy.c:
>
> /*@
>   @ requires n>=0 && \valid(a+(0..n-1)) && \valid(b+(0..n-1)) ;
>   @ ensures \forall integer i ; 0 <= i < n ==> a[i] == b[i] ;
>   @ assigns b[0..n-1] ;
>   @*/
> void copy(int n, double a[], double b[]) {
>   int i = 0;
>
>   /*@
>     @ loop invariant 0<=i<=n;
>     @ loop invariant \forall integer j ; 0<=j<i ==> b[j] == a[j] ;
>     @ loop variant n - i ;
>     @*/
>   while (i < n) {
>     b[i] = a[i];
>     i++;
>   }
> }
>
>
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