Problem with _Bool(when casting to int or with ?:)

ID0001847: This issue was created automatically from Mantis Issue 1847. Further discussion may take place here.

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Id	Project	Category	View	Due Date	Updated
ID0001847	Frama-C	Plug-in > wp	public	2014-07-21	2014-07-21

Reporter	davyg	Assigned To	correnson	Resolution	open
Priority	normal	Severity	minor	Reproducibility	have not tried
Platform	-	OS	-	OS Version	-
Product Version	-	Target Version	-	Fixed in Version	-

Description :

In this example the ensures seems to be impossible to prove whereas it should be easy :

//@ensures (!\result) == (!x); _Bool f(_Bool x) { _Bool y; return (y?x:x); }

I put the bug in Wp category but it can be see as a framaC bug depending from where it comes from.

Additional Information :

This must be due to the transformation of ?: into an if statement with an int local variable which lead more or less to a function like this that can't be proven :

//@ensures (!\result) == (!x); _Bool g(_Bool x) { int t = x; return t; }

This must be due to the lack of information about the cast.

I think that the transformation of ?: should use a _Bool temp variable instead of an int. Or int cast should have a lemma like \forall _Bool x; (x != 0) <==> (((int) x) != 0);