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acsl-language / acsl

Sources for the ANSI/ISO C Specification Language manual
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Arithmetic conversion #14

Open vprevosto opened 7 years ago

vprevosto commented 7 years ago

if e1 and e2 are two expressions of C arithmetic type tau and we do in C res = e1 op e2; (with res also of type tau and res an arithmetic operation), do we always have in ACSL (tau) (e1 op e2) == res.

This is probably wrong for signed arithmetic where overflow results in undefined behavior. What about unsigned arithmetic?

pbaudin commented 6 years ago

I don't really understand the question, but I can say that arithmetic never overflow into ACSL (signed as well as unsigned, even for arithmetic shift operation). That could have to be highlighted.

Also, we could say that the verification of the mentioned ensures clause requires the verification of the precondition of the C operation. ACSL document is there to gives the semantics of ACSL properties, not on how we can prove them. The major question is: does the ACSL document have to present what are C run time errors and how to consider them ?