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[Frama-c-discuss] \at in ACSL assertions

Le lundi 15 novembre 2010 ? 15:33 +0100, Pascal Cuoq a ?crit :
> On Mon, Nov 15, 2010 at 3:07 PM, Yannick Moy <yannick.moy at> wrote:
> > Interesting possibility, to designate the last value at some label
> I initially thought this would allow to talk imprecisely about
> execution paths in ACSL, but now that I think about it, I am not sure
> it is limited to imprecise characterizations of execution paths. Viz:
>   for (i=0; i<=5; i++)
>     {
>     a:
>       j=i;
>     b:
>       j=i;
>     }
>   /*@ assert \at( \at( \at( \at( \at( \at(i, b), a), b), a), b), a) == 2; */

Unless I'm mistaken, this is equivalent to

/*@ assert \at(i, b) == 2; */

since all the other \at operators apply to constant values and are
therefore ignored.

That said, characterizing a label in an inner loop does not seem that
obvious to me. Virgile explained it should be the last one encountered,
but why couldn't it be all the labels at once? In other words, the
logical property would become an invariant of the loop.

Best regards,