On 01.10.2024 07:25, Roberto Bagnara wrote: > On 2024-09-30 15:07, Jan Beulich wrote: >> On 30.09.2024 14:49, Federico Serafini wrote: >>> guest_handle_ok()'s expansion contains a sizeof() involving its >>> first argument which is guest_handle_cast(). >>> The expansion of the latter, in turn, contains a variable >>> initialization. >>> >>> Since MISRA considers the initialization (even of a local variable) >>> a side effect, the chain of expansions mentioned above violates >>> MISRA C:2012 Rule 13.6 (The operand of the `sizeof' operator shall not >>> contain any expression which has potential side effect). >> >> I'm afraid I need to ask for clarification of terminology and alike here. >> While the Misra doc has a section on Persistent Side Effects in its >> Glossary appendix, what constitutes a side effect from its pov isn't >> really spelled out anywhere. Which in turn raises the question whether it >> is indeed Misra (and not just Eclair) which deems initialization a side >> effect. This is even more so relevant as 13.6 talks of only expressions, >> yet initializers fall under declarations (in turn involving an expression >> on the rhs of the equal sign). >> >> All the same of course affects patch 2 then, too. > > MISRA C leaves the definition of "side effect" to the C Standard. > E.g., C18 5.1.2.3p2: > > Accessing a volatile object, modifying an object, modifying a file, > or calling a function that does any of those operations are all > side effects,[omitted irrelevant footnote reference] which are > changes in the state of the execution environment. > > The MISRA C:2012/2023 Glossary entry for "Persistent side effect" > indirectly confirms that initialization is always a side effect.
Hmm, that's interesting: There's indeed an example with an initializer there. Yet to me the text you quote from the C standard does not say that initialization is a side effect - it would be "modifying an object" aiui, yet ahead of initialization being complete the object doesn't "exist" imo, and hence can be "modified" only afterwards. Jan
