--- layout: fc_discuss_archives title: Message 6 from Frama-C-discuss on October 2013 ---
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++; } }