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[Frama-c-discuss] Frama-c: WP issues with Alt-Ergo (but works with Z3)

  • Subject: [Frama-c-discuss] Frama-c: WP issues with Alt-Ergo (but works with Z3)
  • From: moy at adacore.com (Yannick Moy)
  • Date: Wed, 19 Feb 2014 14:25:24 +0100
  • In-reply-to: <5304851D.3060309@lri.fr>
  • References: <B517F47C2F6D914AA8121201F9EBEE6701C76682DC29@Mail1.FCMD.local>, <52D6B7B0.4020005@fr.merce.mee.com> <B517F47C2F6D914AA8121201F9EBEE6701C7BB59DEAB@Mail1.FCMD.local> <5301AF4D.6050500@ocamlpro.com> <B517F47C2F6D914AA8121201F9EBEE6701C7BB53DF2D@Mail1.FCMD.local>, <5302464C.5000906@ocamlpro.com> <B517F47C2F6D914AA8121201F9EBEE6701C7BB53E00B@Mail1.FCMD.local> <5304851D.3060309@lri.fr>
-- Jean-Christophe Filliatre (2014-02-19)
> 
> Hi,
> 
> I know this is not your question, but it seems to me that there are a
> few mistakes in your code:
> 
> - first, "\exists i. A ==> B" shoud rather be "\exists i. A && B" (in
> the post and in the loop invariant)

Interestingly, Why3 issues a warning on such constructs:

warning: form "exists, P -> Q" is likely an error (use "not P \/ Q" if not)

We've copied this warning for Ada contracts in the GNAT compiler:

wrong.ads:3:14: warning: suspicious expression
wrong.ads:3:14: warning: did you mean (for all X => (if P then Q))
wrong.ads:3:14: warning: or (for some X => P and then Q) instead?

Maybe you could have a similar warning in Frama-C.
--
Yannick Moy, Senior Software Engineer, AdaCore