Re: [PATCH 1/3] xen/keyhandler: add missing noreturn attribute

[Jan Beulich <jbeulich@suse.com>]

On 05.06.2025 01:49, victorm.lira@amd.com wrote:
> From: Nicola Vetrini <nicola.vetrini@bugseng.com>
> 
> Function `reboot_machine' does not return, but lacks the `noreturn' attribute,
> therefore causing a violation of MISRA C Rule 2.1: "A project shall not contain
> unreachable code".

Is this (uniformly) true? Looking at ...

> --- a/xen/common/keyhandler.c
> +++ b/xen/common/keyhandler.c
> @@ -251,7 +251,7 @@ static void cf_check dump_hwdom_registers(unsigned char key)
>      }
>  }
> 
> -static void cf_check reboot_machine(unsigned char key, bool unused)
> +static void noreturn cf_check reboot_machine(unsigned char key, bool unused)
>  {
>      printk("'%c' pressed -> rebooting machine\n", key);
>      machine_restart(0);

... generated code here, I can see that the compiler is perfectly able to
leverage the noreturn that machine_restart() has, resulting in no
unreachable code to be generated. That is - neither in source nor in
binary there is any unreachable code. Therefore I'm having a hard time
seeing what the violation is here.

That said, I certainly don't mind the addition of the (seemingly) missing
attribute. Otoh I wonder whether an attribute the removal of which has no
effect wouldn't count as "dead code" or alike, violating some other rule.

Jan