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[Frama-c-discuss] similar assertions not all validated

  • Subject: [Frama-c-discuss] similar assertions not all validated
  • From: Claude.Marche at inria.fr (Claude Marche)
  • Date: Wed, 18 Apr 2012 07:31:55 +0200
  • In-reply-to: <CAC3Lx=aEdtucjWTyiDfDO=QQJ1iOY6hzRVcch_Je5xJtWR_btw@mail.gmail.com>
  • References: <0627805BEE18C14981A31E75C2452AA123AD5E490A@Y000IMRV02.rd1.rf1> <CAC3Lx=aEdtucjWTyiDfDO=QQJ1iOY6hzRVcch_Je5xJtWR_btw@mail.gmail.com>
On 04/17/2012 03:42 PM, David MENTRE wrote:
> Why on your initial code the loop invariants where proven valid? My
> guess is that the invalid invariant or an unproven assertion was used
> as hypothesis to prove the remaining VCs. But I let Frama-C experts
> explain the precise reason.

This is precisely the reason. Although, with the WP plug-in, the status will
not be "valid", but "valid in a context which was not proven valid", 
which is more precise.
Jessie unfortunately does not make the difference.
> My advice would be to avoid using assertions. As they are taken as
> hypothesis for following code, wrong assertions can lead to prove
> incorrect logic annotations. Better is to write correct annotations
> that are proved progressively, one line after the other.

Assertions can be very useful. A better advice could be: look at the 
first unproved VC and fix it, before looking at the VC that come after.


- Claude