MISRA C rules 10.3 and 10.4

On Aug 8, 1:27 pm, Hans-Bernhard Br=F6ker <HBBroe...@t-online.de> wrote:
> David Brown wrote:
> > If the emphasis had been on explicit casting, it would have made sense -
> > "the value may only be *explicitly cast* to a type that is narrower, not
> > implicitly", then it would have made sense.  But (according to the above
> > link),Misra-C allows:
>
> > u16x =3D (U16)(u32a + u32b);
>
> > but not:
>
> > u32x =3D (U32)(u16a + u16b);
>
> If so, that's quite positive achievement.  Too many people believe that
>
>         u16a =3D 40000;
>         u16b =3D 40000;
>         u32x =3D (U32)(u16a + u16b);
>
> will end up with u32x =3D 80000.  IfMISRAcan invent rules that trigger
> on precisely this case and convince those people to write what they
> actually wanted:
>
>         u32x =3D (U32) u16a + (U32) u16b;
>
> that would be a very good thing indeed.

I posted this reply on MISRA-Cs forum because it was the best answer I
could find in the thread. They have now answered:

"10.3 and 10.4 do apply to explicit casts. They are in the section
6=2E10.7 entitled "Explicit conversions (casts)".

Therefore the example above clearly illustrates the intent of MISRA-C
and is correct in its reasoning."

So I think that will conclude the discussion. Thanks for the
contributions everyone.

- Eirik