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[Frama-c-discuss] Frama-C/Jessie: not_assigns and mutable parameter

Pariente Dillon wrote:
> Hello,
>
> Please, what is wrong with this annotated code for which the default
> behavior post-condition PO can not be discharged by Jessie/Why/ATPs (a
> mutable_p var seems to be unexploitable in the hypotheses):
> 	/*@ requires \valid(p) && \valid(q);
> 	assigns *\at(p,Post),p;
> 	*/
> 	int main1(int* p,int* q) { p = q; *p = 1; return 1; }
>   
A general rule: function parameters are not modifiable l-values from the 
caller's point of view.
In other words, the caller cannot see that the implementation uses p as 
a modifiable local variable.

In the contract:

/*@ requires \valid(p) && \valid(q);
    assigns *\at(p,Post),p;
   */
int main1(int* p,int* q) ; 

p is just a parameter and cannot be assigned. assigns p is useless. \at(p,Post) is the same as p.
assigns *\at(p,Post) is wrong because equivalent to assigns *p

- Claude


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