Re: [PATCH] docs/misra: add Rule 16.4

[Jan Beulich <jbeulich@xxxxxxxx>]

On 13.03.2024 01:28, Stefano Stabellini wrote:
> --- a/docs/misra/rules.rst
> +++ b/docs/misra/rules.rst
> @@ -478,6 +478,30 @@ maintainers if you want to suggest a change.
>       - In addition to break, also other unconditional flow control statements
>         such as continue, return, goto are allowed.
>  
> +   * - `Rule 16.4 
> <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_16_04.c>`_
> +     - Required
> +     - Every switch statement shall have a default label
> +     - Switch statements with enums as controlling expression don't need
> +       a default label as gcc -Wall enables -Wswitch which warns (and
> +       breaks the build)

I think this could do with mentioning -Werror.

> if one of the enum labels is missing from the
> +       switch.
> +
> +       Switch statements with integer types as controlling expression
> +       should have a default label:
> +
> +       - if the switch is expected to handle all possible cases
> +         explicitly, then a default label shall be added to handle
> +         unexpected error conditions, using BUG(), ASSERT(), WARN(),
> +         domain_crash(), or other appropriate methods;
> +
> +       - if the switch is expected to handle a subset of all
> +         possible cases, then a default label shall be added with an
> +         in-code comment as follows::
> +
> +             /* only handle a subset of the possible cases */
> +             default:
> +                 break;

Unless it being made crystal clear that mechanically reproducing this
comment isn't going to do, I'm going to have a hard time picking
between actively vetoing or just accepting if someone else acks this.
At the very least, though, the suggested (or, as requested, example)
comment should match ./CODING_STYLE. And it may need placing
differently if I understood correctly what Misra / Eclair demand
(between default: and break; rather than ahead of both).

The only place I'd accept a pre-cooked comment is to cover the
"notifier pattern".

Jan