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# [Frama-c-discuss] arrays in structures

• Subject: [Frama-c-discuss] arrays in structures
• From: agoodloe at gmail.com (Alwyn Goodloe)
• Date: Wed, 28 Jul 2010 08:10:29 -0400

```In trying to understand what happens when valid_range applied is to an
array
in a structure I did the following experiment with
generating the proof conditions in PVS.

For    int a[3];     \valid_range(a,0,2) will (after some unfolding)
produces the
completely understandable proof obligation

{-1}  offset_min[int_P](int_P_a_1_alloc_table!1, a) <= 0 AND
offset_max[int_P](int_P_a_1_alloc_table!1, a) >= 2
........

|-----------------

[1] offset_min[int_P](int_P_a_1_alloc_table!1, a) <= 0

But for   struct SS {a[3];} ;
struct SS xx;

I write
/*@ assert  \valid_range(xx.a,0,2); */

and I thought I would have gotten the same pretty much the same thing, but
nope
the consequent is basically the same, but the antecedent only has the bounds
on the
xx

{-1}  offset_min[SS](SS_xx_1_alloc_table, xx) <= 0 AND
offset_max[SS](SS_xx_1_alloc_table, xx) >= 0

and never mentions the array xx.a and thus the proof becomes stuck.
So I'm guessing that the I need to say more in the assertion or
use something other than valid_range.  Any suggestions would be helpful
since it's kinda preventing me rolling out the tool for others to use.

-A

--
Alwyn E. Goodloe, Ph.D.
agoodloe at gmail.com

Computer Scientist
National Institute of Aerospace
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