[PATCH] score: Simplify _Objects_Is_api_valid()

[Joel Sherrill]

On Thu, Mar 23, 2023 at 11:09 AM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 23.03.23 17:03, Joel Sherrill wrote:
> >
> > On Thu, Mar 23, 2023 at 10:40 AM Sebastian Huber
> > <sebastian.huber at embedded-brains.de
> > <mailto:sebastian.huber at embedded-brains.de>> wrote:
> >
> >     Close #4863.
> >     ---
> >       cpukit/include/rtems/score/objectimpl.h | 4 +---
> >       1 file changed, 1 insertion(+), 3 deletions(-)
> >
> >     diff --git a/cpukit/include/rtems/score/objectimpl.h
> >     b/cpukit/include/rtems/score/objectimpl.h
> >     index c58957ccb5..a1a87b5ccb 100644
> >     --- a/cpukit/include/rtems/score/objectimpl.h
> >     +++ b/cpukit/include/rtems/score/objectimpl.h
> >     @@ -542,9 +542,7 @@ static inline bool _Objects_Is_api_valid(
> >         uint32_t   the_api
> >       )
> >       {
> >     -  if ( !the_api || the_api > OBJECTS_APIS_LAST )
> >     -   return false;
> >     -  return true;
> >     +  return ( 1 <= the_api && the_api <= OBJECTS_APIS_LAST );
> >       }
> >
> >
> > I'd really prefer we avoid compound logical expressions since it
> > becomes something that needs MCDC analysis at higher levels
> > of verification/qualification.
>
> How does this simplify MC/DC analysis? The truth table doesn't change if
> I replace a short-circuit boolean expression with if + return.
>

gcov cannot directly do mcdc analysis but using simple expressions
avoids the introduction of those cases. So gcov reports can be equivalent
of an expensive MCDC analysis tool.

I'm at the FSW this week and one of the NASA Johnson people shared
information on an open source tool and way to use gcov where you
are guaranteed to have gcov reports cover this. I'm going to experiment
with this when I get home. If it is as easy as it sounds, I'll write up
something
on the technique and we can discuss if we want to apply this to RTEMS.
I think we do since it would allow us to use gcov to ensure we do
MCDC level analysis as required by the highest level of all the safety
standards I know.


>
> >
> > Please rewrite using simple logical expressions even if it means
> > two exit paths at the source leve. It's the same machine code.
>
> Yes.
>
Thanks.


>
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