Frama-C-discuss mailing list archives

This page gathers the archives of the old Frama-C-discuss archives, that was hosted by Inria's gforge before its demise at the end of 2020. To search for mails newer than September 2020, please visit the page of the new mailing list on Renater.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Frama-c-discuss] Verifications of calls to unannotated functions

Le lun. 01 f?vr. 2010 15:18:24 CET,
BAUDIN Patrick <Patrick.Baudin at cea.fr> a ?crit :

> Hollas Boris (CR/AEY1) wrote:
> > Consider a function that calls another function:
> >
> > Void f1(...) {
> >   ...
> >   K = f2(...); // (*)
> >   ...
> > }
> >
> > I assume that if f2 has a contract (ie, pre- and postcondition as given by the user), this contract will be used by the verifier at the place of the function call. That is, the prover shows that
> > - the postcondition of f2 implies the wp derived so far
> > - the precondition of f2 is the new precondition for line (*).
> >
> > What happens if f2 isn't annotated? Will the call to f2 just be ignored by the verifier?
> >   
> Please, look at the document "ACSL: ANSI/ISO C Specification Language",
> section 2.3.5 about "default contracts".

To complete Patrick's answer, even if f2 is not annotated, it has a
contract (requires \true; ensures \true;), thus the schema you
described above still holds (of course, you'll have trouble proving
anything related to K after line (*)).
The absence of assigns clause is more problematic. In theory, this
means that f2 could modify any memory location. In practice, if the code
of f2 is given Jessie will infer an over-approximation of the set of
locations that may have been modified (so that any property about
locations which are not in this set still holds after the call). If
only the declaration of f2 is available, frama-c's kernel infer some
assigns clause based on the type of the arguments of f2, but does not
offer any guarantee of correction for this clause (in particular,
it considers that no global is modified directly by f2).

-- 
E tutto per oggi, a la prossima volta.
Virgile