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[Frama-c-discuss] bug with loop invariant, wrong loop invariant gets proven

  • Subject: [Frama-c-discuss] bug with loop invariant, wrong loop invariant gets proven
  • From: Claude.Marche at inria.fr (Claude Marché)
  • Date: Fri, 23 Jan 2009 10:10:30 +0100
  • In-reply-to: <4979803D.2090000@inria.fr>
  • References: <CCFF6F0509A5405C8124C03AA51AF1B1@AHARDPLACE> <4979803D.2090000@inria.fr>

Claude March? wrote:
> third loop: no problem. Beware that your "rewriting" of the loop has the 
> effect that the invariant is now posed after incrementation of i. Which 
> makes things different! No bug here.

To make things clearer: a proper rewriting of

while(++i != length) {}

would be

while(true) {
    i++;
    if (i == length) break;
}




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