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[Frama-c-discuss] WP RTE mem_access condition is Unknown

  • Subject: [Frama-c-discuss] WP RTE mem_access condition is Unknown
  • From: loic.correnson at cea.fr (Loïc Correnson)
  • Date: Mon, 26 May 2014 11:01:07 +0200
  • In-reply-to: <1400876442.8745.6.camel@one>
  • References: <1400876442.8745.6.camel@one>
Hi,
This simply because you don?t have any assigns clause to function b, which then is potentially able to writes everywhere in the memory, and allocate or deallocate any locations.
	L.



Le 23 mai 2014 ? 22:20, Mansour Moufid <mansourmoufid at gmail.com> a ?crit :

> Hi everyone,
> 
> I'm having some difficulty validating a program with the WP RTE plugin.
> 
> This program validates:
> 
>    /*@ requires \valid(x);
>     */
>    void a(int *x, const int y)
>    {
>        if (y > 0) {
>            *x = y;
>        }
>        return;
>    }
> 
> The -wp-rte option gives this output:
> 
>    $ frama-c -wp -wp-rte foo.c
>    [kernel] preprocessing with "gcc -C -E -I.  foo.c"
>    [wp] Running WP plugin...
>    [wp] Collecting axiomatic usage
>    [rte] annotating function a
>    [wp] 1 goal scheduled
>    [wp] [Qed] Goal typed_a_assert_rte_mem_access : Valid
>    [wp] Proved goals:    1 / 1
>         Qed:             1
> 
> But this program does not produce the same result:
> 
>    int b(int x)
>    {
>        return (x > 0);
>    }
>    /*@ requires \valid(x);
>     */
>    void a(int *x, const int y)
>    {
>        if (b(y) != 0) {
>            *x = y;
>        }
>        return;
>    }
> 
> Here is the output of Frama-C with the -wp-print option:
> 
>    $ frama-c -wp -wp-rte bar.c -wp-print
>    [kernel] preprocessing with "gcc -C -E -I.  bar.c"
>    [wp] Running WP plugin...
>    [wp] Collecting axiomatic usage
>    [rte] annotating function a
>    [rte] annotating function b
>    [wp] 1 goal scheduled
>    [wp] [Alt-Ergo] Goal typed_a_assert_rte_mem_access : Unknown
>    [wp] Proved goals:    0 / 1
>         Alt-Ergo:        0  (unknown: 1)
>    ------------------------------------------------------------
>      Function a
>    ------------------------------------------------------------
> 
>    Goal Assertion 'rte,mem_access' (file bar.c, line 10):
>    Assume {
>      (* Domain *)
>      Type: (is_sint32 b_0).
>      (* Heap *)
>      Have: (linked Malloc_1).
>      (* Pre-condition (file bar.c, line 5) in 'a' *)
>      (* Pre-condition: *)
>      Have: (valid_rw Malloc_1 x_1 1).
>      (* bar.c:9: Then *)
>      Have: 0!=b_0.
>    }
>    Prove: (valid_rw Malloc_0 x_1 1).
>    Prover Alt-Ergo returns Unknown
> 
>    ------------------------------------------------------------
> 
> I don't understand why the condition (valid_rw Malloc_0 x_1 1) cannot be
> shown to be true. Could someone please explain why it is "Unknown"?
> 
> Thanks for your time.
> 
> Mansour
> 
> 
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