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[Frama-c-discuss] Specification Examples

  • Subject: [Frama-c-discuss] Specification Examples
  • From: Claude.Marche at inria.fr (Claude Marché)
  • Date: Thu Oct 9 16:18:16 2008
  • In-reply-to: <4FA912B7D4D8468FBACF5B5DDE198385@AHARDPLACE>
  • References: <4FA912B7D4D8468FBACF5B5DDE198385@AHARDPLACE>

Christoph Weber wrote:
> #2: in the second example the preservation of the loop invariant wont work
> 
> 
> 
> /*@ 
>  requires 0 < n;  
>  requires \valid_range(a, 0, n-1) && \valid_range(b, 0, n-1);
>  ensures  \forall int k; 0 <= k < n ==> a[k] == b[k];
> */
> void array_cpy(int* a, int n, int* b){ 
>  /*@ loop invariant 0 <= i <= n && \forall int m; 0 <= m < i  ==> a[m] == b[m];
>  */
>  for(int i = 0;i< n;i++){    
>   a[i]=b[i];    
>  } 
> }
> 
> 
> What am I missing, to get the examples running?

You must take into account the fact that arrays a and b might overlap, 
such as if you call array_cpy as

   array_cpy(t,10,t+1);

in such a case your spec does not hold I think.

- Claude

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