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

  • Subject: [Frama-c-discuss] \at in ACSL assertions
  • From: guillaume.melquiond at inria.fr (Guillaume Melquiond)
  • Date: Mon, 15 Nov 2010 17:10:41 +0100
  • In-reply-to: <1036151116.560170.1289836597250.JavaMail.root@zmbs3.inria.fr>
  • References: <AANLkTimyk_961c8Xk6_U33TAxabBGSeoaRB+EtM-OiBR@mail.gmail.com> <20101115145125.5bad24be@is010235> <4CE13E87.5030807@adacore.com> <2035721159.552419.1289831625935.JavaMail.root@zmbs3.inria.fr> <1289832872.1984.60.camel@guillaume-laptop> <2038674242.558849.1289835496349.JavaMail.root@zmbs3.inria.fr> <1289836319.1984.68.camel@guillaume-laptop> <1036151116.560170.1289836597250.JavaMail.root@zmbs3.inria.fr>
Le lundi 15 novembre 2010 ? 16:56 +0100, Anne Pacalet a ?crit :
> Le 15/11/2010 16:51, Guillaume Melquiond a ?crit :
> > So I will state my point again and refrain from giving an example. It is
> > not obvious to me that \at(v,l) is the value of variable v the last time
> > the program reached label l. It could also be any value of v any time
> > the program reached l.
> 
> Your interpretation looks strange if you consider the annotation :
>    //@ assert x > \at (y, Here);
> Would it means that x is greater than every values y can take
> in any execution ?

As a matter of fact, that's exactly the current ACSL interpretation. The
annotation above is syntactic sugar for

Here42:
//@ assert \at(x,Here42) > \at(y,Here42);

and it precisely states that for any program state at label Here42, the
value of variable x in that state is greater than the value of variable
y in that state.

That said, I see how my interpretation fails when it involves several
labels in a loop, so Virgile's one seems like the only sensible one, if
any.

Best regards,

Guillaume