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[Frama-c-discuss] Problem with \old

  • Subject: [Frama-c-discuss] Problem with \old
  • From: michaelschausten at googlemail.com (Michael Schausten)
  • Date: Thu, 20 May 2010 12:12:25 +0200
Hello,

I'm getting started using Frama-c, but now I'm stuck with a (probably 
simple) problem.
My code:

/*@ ensures (\old(*p) < *p);
*/
void fun(int* p) {
   *p++;
}

I try to prove it with Alt-Ergo via the GWhy-Tool with
frama-c -jessie-analysis -jessie-gui fun.c

It seems to me, that the prover does not make the right usage of \old. 
In the right part of the gWhy-Tool, it says it tries to prove:
integer_of_int32(select(int_P_int_M_p_0_22, p_0)) < 
integer_of_int32(select(int_P_int_M_p_0_22, p_0))
So apparently, it doesn't try to prove \old(*p) < *p, but rather *p < *p 
(which is not provable, of course).

I just can't find out what I'm doing wrong, and I hope you can give me a 
hint what's the problem with my code.